WO2015059866A1 - Wind detection apparatus - Google Patents

Wind detection apparatus Download PDF

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Publication number
WO2015059866A1
WO2015059866A1 PCT/JP2014/004815 JP2014004815W WO2015059866A1 WO 2015059866 A1 WO2015059866 A1 WO 2015059866A1 JP 2014004815 W JP2014004815 W JP 2014004815W WO 2015059866 A1 WO2015059866 A1 WO 2015059866A1
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WO
WIPO (PCT)
Prior art keywords
wind
microphones
sound
sounds
detection apparatus
Prior art date
Application number
PCT/JP2014/004815
Other languages
French (fr)
Inventor
Ryuji Funayama
Jun Sato
Hideo Fukamachi
Tadaaki Sakamoto
Tomoya Takatani
Toshiki Kindo
Naohiro Yasuda
Original Assignee
Toyota Jidosha Kabushiki Kaisha
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Publication of WO2015059866A1 publication Critical patent/WO2015059866A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M9/00—Aerodynamic testing; Arrangements in or on wind tunnels
    • G01M9/06—Measuring arrangements specially adapted for aerodynamic testing
    • G01M9/065—Measuring arrangements specially adapted for aerodynamic testing dealing with flow
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/14—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring differences of pressure in the fluid
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/005—Circuits for transducers, loudspeakers or microphones for combining the signals of two or more microphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/08—Mouthpieces; Microphones; Attachments therefor
    • H04R1/083—Special constructions of mouthpieces
    • H04R1/086—Protective screens, e.g. all weather or wind screens
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
    • H04R2201/40—Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but not provided for in any of its subgroups
    • H04R2201/401—2D or 3D arrays of transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2410/00—Microphones
    • H04R2410/07—Mechanical or electrical reduction of wind noise generated by wind passing a microphone
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
    • H04R2499/10—General applications
    • H04R2499/13—Acoustic transducers and sound field adaptation in vehicles

Definitions

  • the present invention relates to a wind detection apparatus for detecting wind by using a plurality of microphones.
  • a wind noise detection apparatus which comprises a plurality of microphones having substantially the same characteristic and disposed close to each other, to compare the levels of the signals output from the respective microphones and to detect wind noises in response to the difference between the levels of the signals (see for example Patent Document 1).
  • a crosswind warning apparatus which also comprises a plurality of microphones mounted on a vehicle to estimate crosswind around the vehicle from the sounds collected by the microphones outside the vehicle and to calculate the wind power or wind speed, thereby making it possible to warn a driver of the crosswind (see for example Patent Document 2).
  • a vehicle exterior sound detection apparatus which also comprises a plurality of microphones mounted on a vehicle to detect only one detection target sound from the exterior sounds collected by the microphones outside the vehicle (see for example Patent Document 2).
  • the vehicle exterior sound detection apparatus is designed to detect running sounds emitted from the approaching vehicles as vehicle exterior sounds.
  • Patent Document 1 Japanese Published Unexamined Utility Model Application No. H3-69996
  • Patent Document 2 Japanese Patent Application Publication No. 2008-254487
  • Patent Document 3 Japanese Patent Application Publication No. 2011-233090
  • Patent Document 1 only discloses that the wind noise detection apparatus is configured to detect the presence or absence of the wind noises in response to the level difference of the output signals output from the microphones, but does not disclose the particulars about a comparison method of the output signals output from the microphones. For this reason, there is a room to improve for accurately detecting the wind by using a plurality of microphones having substantially the same characteristic and disposed in the vicinity of each other.
  • running vehicle sounds generated by the vehicle with tires running on the public roads have a specific frequency characteristic, and have a high sound pressure component in a frequency band area (hereinafter simply referred to as "running sound band are”) especially in the range of 800Hz to 3000Hz.
  • running sound band are a frequency band area
  • a suitable filter is used to cut off the frequency outside of the running sound band, thereby preventing an erroneous detection caused by the sounds other than the running vehicle sound.
  • the sounds generated by the wind hitting the microphones frequently include a frequency component in the running sound band in the range of 800Hz to 3000Hz. For this reason, under the condition that the wind cannot be accurately detected, only using such a filter as mentioned in the above cannot satisfactorily prevent the erroneous detection caused by the wind sound.
  • the present invention has been made to solve the problems of the prior art as described above, and has an object to provide a wind detection apparatus which can accurately detect the wind.
  • the wind detection apparatus (1) comprises a plurality of microphones, a frequency characteristic acquisition unit that acquires frequency characteristics from signals of sounds detected by the plurality of microphones, the frequency characteristics each representing a sound pressure at each of frequency band areas respectively divided at a predetermined frequency interval, a frequency characteristic comparison unit that compares the frequency characteristics of the plurality of microphones acquired by the frequency characteristic acquisition unit, and a wind determination unit that determines that the sounds detected by the plurality of microphones are wind sounds, respectively, when a difference among the sound pressures of the plurality of microphones is detected throughout the frequency band areas excluding a low frequency band area in a range of zero to a predetermined frequency in accordance with comparison results of the frequency characteristic comparison unit.
  • the wind detection apparatus is adapted to determine that the sounds detected by the plurality of microphones are wind sounds, respectively, when the difference among the sound pressures of the plurality of microphones is detected by the wind determination unit throughout the predetermined frequency band areas, based on the sound pressures in respective frequency band areas of the plurality of microphones acquired by the frequency characteristic acquisition unit.
  • the wind detection apparatus can determine whether or not the sounds detected by the plurality of microphones are respectively caused by the wind by utilizing the fact that there is a remarkable difference seen among the frequency characteristics of the sound pressures acquired when the wind hits the plurality of microphones even if the sound signals detected by the plurality of microphones include frequency components of the sounds such as the running vehicle sounds other than the wind sounds. Therefore, the wind detection apparatus according to the present invention can accurately detect the wind.
  • the wind detection apparatus as set forth in (1), (2) may further comprise a storage unit that preliminarily stores as a default value data indicating dispersions of the sound pressures in each frequency band area in the frequency characteristics of the plurality of microphones acquired from the signals of the sounds detected by the plurality of microphones in absence of the wind, and in which the wind determination unit determines that the sounds detected by the plurality of microphones are wind sounds, respectively, when the difference among the sound pressures of the plurality of microphones is larger than the default value.
  • the wind detection apparatus is adapted to have the wind determination unit determine that the sounds detected by the plurality of microphones are wind sounds, respectively, when the difference among the sound pressures of the plurality of microphones is large in comparison with the default value acquired from the signals of the sounds of the plurality of microphones in the absence of the wind. This leads to the fact that the wind detection apparatus according to the present invention can accurately detect the wind as compared with the case in which the difference among the sound pressures of the plurality of microphones is detected throughout the predetermined frequency band area as seen from the above description (1).
  • the frequency characteristic comparison unit compares dispersions of the sound pressures in the frequency characteristics of the plurality of microphones acquired by the frequency characteristic acquisition unit, and the wind determination unit determines that the sounds detected by the plurality of microphones are wind sounds, respectively, when the dispersion of the sound pressures of the microphone having a high sound pressure is smaller than the dispersion of the sound pressures of the microphone having a low sound pressure, in accordance with comparison results of the frequency characteristic comparison unit.
  • the wind detection apparatus is adapted to have the wind determination unit determine that the sounds detected by the plurality of microphones are wind sounds, respectively, when the dispersion of the sound pressures having a high sound pressure is smaller than the dispersion of the sound pressures having a low sound pressure.
  • the wind detection apparatus can detect that the dispersion of the sound pressures of a microphone having a high sound pressure is smaller than the dispersion of the sound pressures of another microphone having a low sound pressure, thereby making it possible to more accurately detect the wind.
  • the present invention can provide a wind detection apparatus which can accurately detect the wind.
  • Fig. 1 is a diagram showing frequency characteristics of sounds detected by the two microphones in the absence of wind.
  • Fig. 2 is a diagram showing frequency characteristics of sounds detected by the two microphones hit by the wind.
  • Fig. 3A is a view for explaining sound pressure variations of sound and wind detected by the two microphones.
  • Fig. 3B is a view for explaining sound pressure variations of sound and wind detected by the two microphones.
  • Fig. 4 is a first embodiment of a wind detection apparatus according to the present invention, and a block diagram showing the constitution of the wind detection apparatus.
  • Fig. 5A is a view showing a first embodiment of the wind detection apparatus according to the present invention, and a microphone forming a part of a microphone array constituting a part of the wind detection apparatus and mounted on a vehicle.
  • Fig. 5B is a view showing a first embodiment of the wind detection apparatus according to the present invention, and a microphone forming a part of a microphone array constituting a part of the wind detection apparatus and mounted on a vehicle.
  • Fig. 5C is a view showing a first embodiment of the wind detection apparatus according to the present invention, and a microphone forming a part of a microphone array constituting a part of the wind detection apparatus and mounted on a vehicle.
  • Fig. 6 is a first embodiment of the wind detection apparatus according to the present invention, and a flow chart showing an example of a process relating to the wind detection.
  • Fig. 7 is a first embodiment of the wind detection apparatus according to the present invention, and a flow chart showing another example of the process relating to the wind detection.
  • Fig. 5B is a view showing a first embodiment of the wind detection apparatus according to the present invention, and a microphone forming a part of a microphone array constituting a part of the wind detection apparatus and mounted on a vehicle.
  • FIG. 8 is a first embodiment of the wind detection apparatus according to the present invention, and a flow chart showing a further example of the process relating to the wind detection.
  • Fig. 9 is a second embodiment of the wind detection apparatus according to the present invention, and a block diagram showing a schematic constitution of a warning device using the wind detection apparatus.
  • Fig. 10 is a third embodiment of the wind detection apparatus according to the present invention, and a block diagram showing a schematic constitution of the warning device using the wind detection apparatus.
  • Fig. 11A is a third embodiment of the wind detection apparatus according to the present invention, and shows an explanation view of a mesh structure to be mounted on each of the microphones.
  • FIG. 11B is a third embodiment of the wind detection apparatus according to the present invention, and shows an explanation view of a mesh structure to be mounted on each of the microphones.
  • Fig. 11C is a third embodiment of the wind detection apparatus according to the present invention, and shows an explanation view of a mesh structure to be mounted on each of the microphones.
  • the wind detection apparatus can be applied to various applications, but the embodiments described below will be explained raising examples to be applied to a system for having microphones respectively catch sounds generated by other surrounding running vehicles (other vehicles) outside of a driver's vehicle (hereinafter simply referred to as "own vehicle” to detect other vehicles, and a system for warning the detection of the other running vehicles to a driver.
  • GCC-PHAT generalized cross correction phase transform
  • CSP cross-power spectrum phase analysis
  • the sound produced by a vehicle with tires on a public road has a high sound pressure component in a running sound band area (800Hz ⁇ 3000Hz) as described above.
  • the frequency outside of the running sound band area is generally designed to have the above correlation values of sounds be out of targets to be calculated to prevent the erroneous detection caused by the sounds other than the running vehicle sounds.
  • the running sound band includes a frequency component of the sound other than the running vehicle sound.
  • the sound pressure increases throughout the running sound band.
  • FIGS. 1 and 2 showing frequency characteristics of the sounds detected by the microphones, respectively are compared, the frequency characteristic of the sound in the presence of the wind hitting the microphone (see FIG. 2 is seen as being increased in the sound pressure throughout the entire frequency band area (0 ⁇ 12000Hz in an illustrated example) including the running sound band (800Hz ⁇ 3000Hz) as compared with the frequency characteristic of the sound in absence of the wind (see FIG. 1).
  • the current technique determines that when the wind hits the microphone, the sound caused by the wind hitting the microphone is deemed to be a running vehicle sound, thereby leading to erroneously detecting the existence of the other running vehicle in the vicinity of the own vehicle.
  • This erroneous detection of the other vehicle leads to giving an unnecessary warning to the driver. It will therefore be understood that the above erroneous detection is one of important problems to be solved.
  • the wind detection apparatus according to the embodiment of the present invention is constructed by utilizing the fact that when the wind hits the microphone, the sound pressure varied for every frequency band area is characteristic., viz., causing a remarkable difference between the frequency characteristics of the sounds detected by the two microphones.
  • the wind detection apparatus according to the embodiment of the present invention thus constructed can determine whether or not the sounds are affected by the wind.
  • FIG. 1 is a diagram showing frequency characteristics acquired by the signals of the sounds detected by the two microphones in the absence of wind.
  • FIG. 2 is a diagram showing frequency characteristics acquired by the signals of the sounds detected by the two microphones hit by the wind.
  • the horizontal axis represents the frequency (Hz)
  • the vertical axis represents the sound pressure level (dB).
  • the frequency characteristics shown by the broken line are obtained from one of microphones (microphone 11), while the frequency characteristics shown by the solid line are obtained from the other of microphones (microphone 12).
  • the frequency characteristics shown in FIGS. 1 and 2 are obtained from the signals of the sound detected by the two microphones 11, 12.
  • the sound energies (sound pressures SP1, SP2) caught by the two microphones 11, 12 are substantially the same with each other in the frequency band areas excluding one part of low frequency band areas in the vicinity of zero, thereby allowing both of the frequency characteristics to be matched with each other due to the fact that the two microphones 11, 12 are arranged close to each other, for example, at a distance of 10cm.
  • the sound pressure SP1 of one of the microphone 11 is, as shown in FIG. 2, higher in level than the sound pressure SP2 of the other of the microphone 12 throughout the entire frequency band area. This is due to the following reasons.
  • the wind When the wind is considered to be blowing at a wind speed of 10m/sec from the direction laterally inclined with respect to the two microphones 11, 12 as shown in FIG. 3B, the wind firstly hits one of the microphone 11, and then hits the other of the microphone 12 after about 10msec elapses. This means that the time difference appearing with the effect of the wind with respect to the two microphones 11, 12, is about 10msec or less.
  • the sound is a vibration that is alternately generated by the density state of air or wind.
  • the running sound band area is about 800Hz ⁇ 3000Hz, while the air density vibration generated by the wind is far less, i.e., far slowly than that of the running sound.
  • the mass of air containing the vibration of air of the running sound is in the form of the two microphones 11, 12, hit by the wind, so that the sound pressure of each of the two microphones 11, 12 in the presence of the wind becomes larger in the almost entire frequency band area excluding the extremely small portion of the low frequency band area than that of each of the two microphones 11, 12 in the absence of the wind (see FG. 1 and FIG. 2.
  • This effect is substantially constant regardless of the frequency due to the above reason.
  • the wind with the wind speed 10m/sec influencing the change of the sound pressure of the microphone 11 reaches the microphone 12 spaced apart at a distance of 10cm from the microphone 11 approximately 10msec after the change of the sound pressure of the microphone 11, thereby leading to the fact that at this time, the change of the sound pressure of the microphone 12 is also observed.
  • the difference of the sound pressures in each of the frequency band areas between the one and the other of the two microphones 11, 12 is observed at the moment when the wind firstly hits the microphone 11, the sound pressure SP1 of the microphone 11 is higher than the sound pressure SP2 of the microphone 12 throughout the entire frequency band area (frequency band area shown by a symbol "WF" in FIG. 2) excluding the low frequency band area in a predetermined range from zero as shown in FIG. 2.
  • the sound pressure difference (sound pressure difference shown by a symbol "Df" in FIG. 2) of the sounds detected by the two microphones 11, 12 in each of the frequency band areas makes it possible to determine whether or not the sounds detected by the two microphones 11, 12 are influenced by the wind.
  • FIGS. 4 to 8 show a first embodiment of the wind detection apparatus according to the present invention.
  • the wind detection apparatus As shown in FIG. 4, the wind detection apparatus according to the present invention is provided with a microphone array 10, and an Electronic Control Unit (hereinafter simply referred to as an "ECU") 20.
  • ECU Electronic Control Unit
  • the microphone array 10 comprises a plurality of microphones having substantially the same characteristic (two microphones 11, 12 in this embodiment).
  • the microphones 11, 12 of the microphone array 10 are spaced apart at a distance of 10cm from each other, and thus disposed close to each other in the same arrangement state to catch the sounds respectively reaching the two microphones 11, 12 from the same direction.
  • the wind detection apparatus 1 is mounted on the own vehicle, and the two microphones 11, 12 constituting the microphone array 10 are adapted to detect the sounds generated outside of the own vehicle, the sounds including a wind sound, a running sound generated from other vehicle surrounding the own vehicle and the like.
  • the microphone array 10 is installed at a suitable location on the own vehicle.
  • the microphone array 10 may be installed on the bumper portion B of the vehicle P as shown in FIG. 5A, or otherwise may be installed in the vicinity of the windshield in the bonnet BN of the vehicle P as shown in FIG. 5B. Further, the microphone array 10 may be installed in the roof carrier R which is provided on the ceiling portion of the vehicle P as shown in FIG. 5C.
  • the two microphones 11, 12 constituting the microphone array 10 are adapted to output the signals of the sounds outside of the vehicle detected by the two microphones 11, 12, respectively, to the ECU 20.
  • the ECU 20 is an electronic control unit including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and others, which are not shown in the drawings, to carry out the process according to the wind detection.
  • the ECU 20 includes an analog/digital (A/D) converter unit 21, a spectrum analyzer unit 22, a sound pressure/dispersion comparison unit 23, a wind determination unit 24, and a memory unit 25.
  • A/D analog/digital
  • the A/D converter unit 21 is illustrated by a functional block for A/D converting the sound signals (analog signals) output from the two microphones 11, 12 into digital signals, respectively.
  • the A/D converter unit 21 is configured to output the A/D converted sound signals to the spectrum analyzer unit 22.
  • the spectrum analyzer unit 22 is illustrated by a functional block for acquiring the frequency characteristic (spectrum) representing the sound pressure of each frequency band area divided at a predetermined frequency interval, from the sound signals input through the A/D converter unit 21 from the two microphones 11, 12, the frequency characteristic (spectrum) to be acquired is a frequency characteristic as shown in FIG. 2.
  • the spectrum analyzer unit 22 constitutes a frequency characteristic acquisition unit as set forth in the present invention.
  • the spectrum analyzer unit 22 is adapted to divide the two input sound signals of the two microphones 11, 12 into frequency band areas (for example, each having a frequency interval of 100Hz) by using a Fast Fourier Transform (FFT) to calculate the sound pressures of the two microphones 11, 12, in each frequency band area (performing spectral analysis).
  • FFT Fast Fourier Transform
  • the spectrum analyzer unit 22 may, for example, be configured to calculate FFT for every 10Hz. In this case, the spectral analyzer unit 22 may perform the FFT calculation ten times to average the sound pressures acquired by this calculation, thereby allowing the averaged values to be the sound pressures for 100Hz, respectively.
  • the sound pressure/dispersion comparison unit 23 is illustrated by a functional block for comparing the frequency characteristics (spectrum) of the two microphones 11, 12 obtained by the spectrum analyzer unit 22.
  • the sound pressure/dispersion comparison unit 23 constitutes a frequency characteristic comparison unit as set forth in the present invention.
  • the sound pressure/dispersion comparison unit 23 is adapted to compare the sound pressures at each frequency band area obtained by the spectral analysis for the sound signals of the two microphones 11, 12, and to compare the dispersion of the sound pressures.
  • the wind determination unit 24 is illustrated by a functional block for determining whether or not the sounds detected by the two microphones 11, 12 are respectively wind sounds based on the comparison results by the sound pressure/dispersion comparison unit 23.
  • the wind determination unit 24 constitutes a wind determination unit as set forth in the present invention.
  • the wind determination unit 24 is adapted to determine that the sounds detected by the two microphones 11, 12 are respectively wind sounds when the difference between the sound pressure SP1 of the microphone 11 and the other sound pressure SP2 of the microphone 12, i.e., the sound pressure difference Df between the two microphones 11, 12, is detected throughout the frequency band area WF, which is constituted by the aforementioned frequency band areas excluding the low frequency band area in the range of zero to the predetermined low frequency, in accordance with the frequency characteristics as shown in FIG. 2.
  • the reason why the low frequency band area in the range of zero to the predetermined low frequency is excluded from among the frequency band areas which include a detection target of the sound pressure difference will be described hereinafter.
  • the reason is due to the fact that the sound difference Df between the sound pressures of the two microphones 11, 12 sufficiently does not appear in the low frequency band area even if the wind is blowing.
  • the low frequency band area to be excluded from among the detection targets may be in the range of, for example, 0 ⁇ 1000Hz as shown in FIG. 2.
  • the wind determination unit 24 is adapted to determine that the microphone 11 catches the wind sound at the moment (see FIG. 3) when the wind firstly strikes the microphone 11, and to detect, at this time, the difference Df (see FIG. 2) between the sound pressures of the two microphones 11, 12.
  • the difference Df see FIG. 2
  • the wind determination unit 24 may determine in accordance with the comparison results by the sound pressure/dispersion comparison unit 23 that the microphone 11 catches the wind sound when the numerical percentage of the frequency band areas in which the sound pressure SP1 of the microphone 11 is higher than the sound pressure SP2 of the microphone 12 I is equal to or more than a predetermined ratio.
  • the wind determination unit 24 may determine in accordance with the comparison results by the sound pressure/dispersion comparison unit 23 that the microphone 11 catches the wind sound when the total value totaling in all of the frequency band areas the differences obtained by reducing the sound pressures SP2 of the microphone 12 from the sound pressures SP1 of the microphone 11 for each of the frequency band areas.
  • the memory unit 25 is adapted to store the data indicating the dispersion of the sound pressures in each of frequency band areas of the two microphones 11, 12 calculated from the sound signals respectively detected by the two microphones 11, 12 in the absence of the wind, viz., the data of the frequency characteristics as shown in FIG 1 for example as default values.
  • the memory unit 25 constitutes a storage unit as set forth in the present invention.
  • the wind determination unit 24 is adapted to determine with reference to the data (default values) stored in the memory unit 25 that the sounds respectively detected by the two microphones 11, 12 are wind sounds, respectively, when the difference Df between the sound pressures of the two microphones 11, 12 is larger than the default value.
  • the wind determination unit 24 is adapted to determine in accordance with the comparison results by the sound pressure/dispersion comparison unit 23 that the sounds respectively detected by the two microphones 11, 12 are wind sounds, respectively, when the dispersion of the sound pressure SP1 of the microphone 11(see FIG. 2) having a high sound pressure is smaller than the dispersion of the sound pressure SP2 of the microphone 12 having a low sound pressure.
  • the reason why the previous determination can be performed is based on the following description. This reason is due to the fact that the pressure raised by the effect of the wind leads to suppressing the sound from being vibrated. In other words, it can be estimated that the microphone 11 having the high sound pressure is to receive a relatively small pressure generated under the influence of the wind, thereby making it possible to relatively reduce the dispersion (variation amount) of the sound pressure SP1 of the microphone 11.
  • the memory unit 25 is adapted to store, as a lookup table, the data indicating the relationships between the wind speeds and the differences of the sound pressures of the two microphones 11, 12 in each of frequency band areas of the two microphones 11, 12.
  • the wind speeds and the differences between the sound pressures of the two microphones 11, 12 are preliminarily acquired through repeated experiments.
  • the data indicating the differences between the sound pressures of the two microphones 11, 12 the average value of the differences between the sound pressures of the two microphones 11, 12 in each of frequency band areas of the two microphones 11, 12 to be obtained through the first method, or otherwise the total value of the differences between the sound pressures of the two microphones 11, 12 to be obtained through the second method is used.
  • the wind determination unit 24 is adapted to estimate the wind strength (wind speed) in accordance with the average value or the total value of the difference between the sound pressures of the two microphones 11, 12.
  • the reason why the wind determination unit 24 can estimate the wind strength (wind speed) is due to the fact that the stronger the wind is (the higher the wind speed is), the above difference between the sound pressures is increased.
  • FIG 6 is a flowchart showing an example of the process relating to the wind detection.
  • the ECU 20 is input with the sound signals respectively detected by the two microphones 11, 12 (Step S1).
  • the sound signals (analog signals) input into the ECU 20 is converted into digital signals, respectively, through the A/D converter unit 21, and then input into the spectrum analyzer unit 22.
  • the spectrum analyzer unit 22 then divides the input sound signals (digital signals) of the two microphones 11, 12 for example into a plurality of frequency band areas of 100Hz each by using the Fast Fourier Transform (FFT) (Step S2), and to calculate the sound pressure for every frequency band area of each of the two microphones 11, 12 (Step S3).
  • the wind detection apparatus therefore can acquire the frequency characteristics (spectrum) as shown in FIG. 2.
  • the sound pressure/dispersion comparison unit 23 then compares the sound pressures of the two microphones 11, 12 in each of the frequency band areas in the frequency characteristics (spectrum) acquired by the spectrum analyzer unit 22 (Step S4).
  • the wind determination unit 24 determines whether or not the difference Df between the sound pressures (see FIG. 2) of the two microphones 11, 12 is detected throughout the frequency band area WF, which is constituted by the plurality of said divided frequency band areas excluding the low frequency band area in the range of zero to the predetermined low frequency, in accordance with the comparison results obtained by the sound pressure/dispersion comparison unit 23 (Step S5).
  • Step S5 the wind determination unit 24 determines that the difference Df between the sound pressures of the two microphones 11, 12 is detected throughout the frequency band area WF ("YES" in Step S5), the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are caused by the wind to output the signal indicative of the determination results showing that the sounds are caused by the wind (Step S6). The above process of the wind detection apparatus is repeated thereafter.
  • the wind determination unit 24 determines that the difference Df between the sound pressures of the two microphones 11, 12 is not detected throughout the frequency band area WF ("NO" in Step S5), the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are not caused by the wind to output the signal indicative of the determination results showing that the sounds are not caused by the wind. The above process of the wind detection apparatus is repeated thereafter.
  • FIG 7 is a flowchart showing another example of the process relating to the wind detection to be carried out by the wind detection apparatus according to the present invention.
  • the process flow shown by this flow chart is assumed to show a case in which the determination results in the Step 5 is "YES" in the flow chart shown in FIG. 6 (viz., a case in which the difference between the sound pressures of the two microphones 11, 12 is detected over the predetermined frequency band area).
  • the wind determination unit 24 in the ECU 20 reads out from the memory unit 25 the default value preliminarily obtained, viz., the data indicating the dispersion of the sound pressures of the two microphones 11, 12 in the absence of the wind (Step S11).
  • the wind determination unit 24 determines whether or not the difference Df between the sound pressures (see FIG. 2) of the two microphones 11, 12 in accordance with the comparison results by the sound pressure/dispersion comparison unit 23 is larger than the default value read out from the memory unit 25 (Step S12).
  • the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are caused by the wind (Step S13) to output the signal indicative of the determination results showing that the sounds are caused by the wind. The above process of the wind detection apparatus is repeated thereafter.
  • the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are not caused by the wind to output the signal indicative of the determination results showing that the sounds are not caused by the wind. The above process of the wind detection apparatus is repeated thereafter.
  • FIG 8 is a flowchart showing a further example of the process relating to the wind detection to be carried out by the wind detection apparatus according to the present invention.
  • the process flow shown by this flow chart is assumed to show a case in which the determination result in the Step 5 is "YES" in the flow chart shown in FIG. 6 (viz., a case in which the difference between the sound pressures of the two microphones 11, 12 is detected over the predetermined frequency band area).
  • the sound pressure/dispersion comparison unit 23 in the ECU 20 compares the dispersions of the sound pressures of the two microphones 11, 12 for each of the frequency band areas in accordance with the frequency characteristics obtained by the spectrum analyzer unit 22 (spectrum) (Step S21).
  • the wind determination unit 24 determines in accordance with the comparison results obtained by the sound pressure/dispersion comparison unit 23 whether or not the dispersion of the sound pressure SP1 of the microphone 11 (see FIG. 2) having a high sound pressure is smaller than the dispersion of the sound pressure SP2 of the microphone 12 having a low sound pressure (Step S22).
  • the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are caused by the wind to output the signal indicative of the determination results showing that the sounds are caused by the wind (Step S23). The above process of the wind detection apparatus is repeated thereafter.
  • the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are not caused by the wind to output the signal indicative of the determination results showing that the sounds are not caused by the wind. The above process of the wind detection apparatus is repeated thereafter.
  • the wind detection apparatus 1 is configured to have the wind determination unit 24 in the ECU 20 determine that the sounds respectively detected by the two microphones 11, 12 are caused by the wind when the difference Df between the sound pressure of the microphone 11 and the sound pressure of the microphone 12 is detected throughout the predetermined frequency band area WF from among the sound pressures of the two microphones 11, 12 in each of the frequency band areas analyzed by the spectrum analyzer unit 22 (frequency characteristics shown in FIG. 2).
  • the wind detection apparatus 1 can determine whether or not the sounds detected by the two microphones 11, 12 are respectively caused by the wind by utilizing the fact that there is a remarkable difference seen between the frequency characteristics of the sound pressures SP1, SP2 acquired when the wind hits the two microphones 11, 12 as shown in FIG. 2 even if the sound signals detected by the two microphones 11, 12 include frequency components of the sounds such as the running vehicle sounds other than the wind sounds as previously mentioned. Therefore, the wind detection apparatus 1 according to the present embodiment can more accurately detect the wind.
  • the wind detection apparatus 1 is configured to determine that the sounds detected by the two microphones 11, 12 are respectively caused by the wind when the difference Df between the sound pressures of the two microphones 11, 12 (see FIG. 2) is large as compared with the default value (frequency characteristic shown in FIG. 1) acquired from the sound signals of the two microphones 11, 12 in the absence of the wind. This leads to the fact that the wind detection apparatus 1 according to the present embodiment can more accurately detect the wind as compared with the case in which the difference Df between the sound pressures of the two microphones 11, 12 is detected throughout the predetermined frequency band area WF.
  • the wind detection apparatus 1 is configured to determine that the sounds detected by the two microphones 11, 12 are respectively caused by the wind when the ECU 20 detects the fact that the dispersion of the sound pressure SP1 of the microphone 11 (see FIG. 2) having the high sound pressure is smaller than the dispersion of the sound pressure SP2 of the microphone 12 having the low sound pressure.
  • the wind detection apparatus 1 can detect the fact that the dispersion of the sound pressure SP1 of the microphone 11 having the high sound pressure becomes smaller than the dispersion of the sound pressure SP2 of the microphone 12 having the low sound pressure.
  • FIG. 9 shows a second embodiment of the wind detection apparatus according to the present invention.
  • the second embodiment of the wind detection apparatus is partly constituted by a warning device which is operative together with the wind detection apparatus according to the first embodiment previously mentioned.
  • the warning device 2 As shown in FIG. 9, the warning device 2 according to the present embodiment is provided with the wind detection apparatus 1 according to the first embodiment previously mentioned, an ECU 30, and a display unit 35.
  • the microphones 11, 12 in a microphone array 10 constituting a part of the wind detection apparatus 1 is adapted to output the vehicle outside sound signals respectively detected by the two microphones 11, 12 not only to the ECU 30 but also to the ECU 20 (see FIG. 4) of the wind detection apparatus 1.
  • the ECU 30 is an electronic control unit which includes a CPU, a ROM, a RAM, and others.
  • the ECU 30 includes an analog/digital (A/D) conversion unit 31, a running vehicle detection unit 32, and a warning mode control unit 33.
  • A/D analog/digital
  • the A/D conversion unit 31 is illustrated by a functional block for A/D converting the sound signals (analog signals) output from the two microphones 11, 12 into the digital signals, respectively. Further, the A/D conversion unit 31 is adapted to output the sound signals A/D converted to the running vehicle detection unit 32.
  • the running vehicle detection unit 32 is illustrated by a functional block for detecting running vehicles (other vehicles) around the own vehicle from the sound signals input through the A/D conversion unit 31 from the two microphones 11, 12.
  • the running vehicle detection unit 32 detects the running vehicles, the running vehicle detection unit 32 is adapted to output the detection information in response to the detection modes.
  • the warning mode control unit 33 is illustrated by a functional block for controlling the process to issue warnings (alert) to the driver in accordance with the detection information output from the running vehicle detection unit 32, and the wind determination results output from the wind detection apparatus 1.
  • the warning mode control unit 33 is adapted to output a control signal indicative of the warning to the display unit 35.
  • the warning mode control unit 33 is adapted to output a control signal for performing the predetermined alert when the running vehicle is detected by the running vehicle detection unit 32, and further to output a control signal for changing the alert modes, viz., one alert mode to the other alert mode when the wind is detected by the wind detection apparatus 1.
  • the display unit 35 includes a monitor or the like for performing an alarm display, and a speaker for outputting sound.
  • the display unit 35 When the running vehicle is detected by the running vehicle detection unit 32 in the ECU 30, the display unit 35 outputs the information prompting the warning to the driver through the speaker, or otherwise displays on the monitor in accordance with the control signal output from the warning mode control unit 33.
  • the display unit 35 may audio output a message, for example, "the running vehicle approaching", or otherwise may display on the monitor.
  • the display unit 35 is adapted to change the output of the alert or the display mode in accordance with the control signal output from the warning mode control unit 33.
  • the display unit 35 may audio output a message, for example, "the strong wind makes it for the warning system to be under no operation", or otherwise may display information to this effect on the monitor, thereby stopping the alert to the driver.
  • the present invention does not necessarily limit the case in which it is determined that the sounds caught by the microphones 11, 12 are caused by the wind, but may include a case in which the wind speed estimated by the wind determination unit 24 (see FIG. 4) is equal to or faster than a predetermined speed.
  • the present invention does not limit the case in which any alert as previously mentioned is not performed, but may include a case in which the intensity of the alert (for example, volume of the warning sound) in response to the estimated wind is varied. More specifically, the present invention may make stronger the intensity of the alert by determining that the running vehicle detection is not sufficiently affected by the wind if the wind speed is low. On the contrary, the present invention may make weaker the intensity of the alert by regarding the confidence of the running vehicle detection as being low due to the fact that the running vehicle detection is strongly affected by the wind if the wind speed is high.
  • the intensity of the alert for example, volume of the warning sound
  • the warning device 2 using the wind detection apparatus 1 is adapted to perform the predetermined alert when the wind detection apparatus 1 detects the running vehicles around the own vehicle, and further to change the alert modes when the wind detection apparatus 1 detects the wind in accordance with the information of sounds outside of the own vehicle collected by the ECU 30 using the microphone array 10, i.e., the two microphones 11, 12.
  • the wind detection apparatus can reduce unnecessary alerts to the driver, and can solve such a problem as giving an erroneous alert to the driver despite the sound which is not the running vehicle sound as seen in the state of the art. This contributes greatly to the improvement of the reliability of the warning device 2.
  • FIGS. 10 and FIG. 11 show a third embodiment of the wind detection apparatus according to the present invention.
  • the third embodiment of the wind detection apparatus is partly constituted by a running vehicle detection apparatus, using the wind detection apparatus according to the first embodiment previously mentioned.
  • the running vehicle detection apparatus 3 is provided with a plurality of wind detection apparatuses (in the illustrated example, three wind detection apparatuses 1, 1a and 1b), and an ECU 40.
  • the three wind detection apparatuses 1, 1a and 1b respectively include a microphone array 10 (two microphones 11, 12), a microphone array 10a (two microphones 11a, 12a), and a microphone array 10b (two microphones 11b, 12b) which are respectively different in wind preventing effect from one another.
  • the wind preventing effects to be performed by the microphone array 10, the microphone array 10a, and the microphone array 10b, respectively, can be realized by attaching mesh-like structures (hereinafter simply referred to as "mesh structures") 13 on the front surfaces of the vibration plates of the two microphones 11, 12, 11 a, 12a, 11b, 12b.
  • the mesh structure 13 thus attached can suppress the two microphones 11, 12, 11 a, 12a, 11b, 12b (hereinafter simply referred to as "each microphone 11 or the like”) from catching the wind sound, however, gives rise to lowering reducing the energy of sound to be input to each microphone 11 or the like, thereby simultaneously causing the sensitivity of each microphone 11 or the like to be reduced.
  • the present embodiment is configured to make different the wind preventing effects and the sensitivities for the microphone arrays 10, 10 a, 10b, by preparing a plurality of mesh structures 13 different in mesh roughness, and attaching each of the mesh structures 13 to each microphone 11 or the like. More specifically, the mesh structures 13a relatively coarse in mesh roughness, and the mesh structures 13b relatively fine in mesh roughness are used as shown in FIG. 11B and FIG. 11C.
  • the mesh structure 13a relatively coarse in mesh roughness to be used can reduce the wind preventing effect, but can reduce the microphone sensitivity to a smaller level. This means that the microphone array (for example, microphone array 10) using the mesh structure 13a relatively coarse in mesh roughness can catch the wind sound even with the weaker wind.
  • the mesh structure 13b relatively fine in mesh roughness is used, the wind preventing effect can be heightened, however, the microphone sensitivity is greatly reduced. This means that the microphone array (for example microphone array 10a) using the mesh structure 13a relatively fine in mesh roughness cannot catch the wind sound without the strong wind.
  • the two microphones 11, 12, 11a, 12a, 11b 12b in the microphone arrays 10, 10a, 10b partly constituting the wind detection apparatus 1, 1a, 1b are adapted to output the respective signals indicative of the detected sounds outside of the vehicle to the ECU 40 through the signal line 14 (see FIG. 11A).
  • the ECU 40 is an electronic control unit including a CPU, a ROM, a RAM, and others.
  • the ECU 40 includes a microphone array selection unit 41, and a running vehicle detection unit 42.
  • the microphone array selection unit 41 is illustrated by a functional block for A/D converting into digital signals the sound signals (analog signals) of the two microphones 11, 12, 11a, 12a, 11b, 12b, respectively, output from the microphone arrays 10, 10a, 10b, and for thereafter selecting the outputs of the microphone arrays 10, 10 a, 10b to be used for the running vehicle detection.
  • the microphone array selection unit 41 is adapted to determine whether the microphone arrays 10, 10 a, 10b catch or do not catch the wind sounds in an ascending order of wind preventing effect (in a descending order of microphone sensitivity) in accordance with the sound signals respectively output from the microphone arrays 10, 10 a, 10b.
  • the microphone array selection unit 41 is adapted to search the microphone having a larger wind preventing effect (lower microphone sensitivity) and to select the microphone array determined not to catch the wind sound, viz., to select the output of the microphone array to use the running vehicle detection when the wind sound is determined to be caught.
  • the running vehicle detection unit 42 is illustrated by a functional block for detecting vehicles (other vehicles) around the own vehicle by using the output (sound signals) of the microphone array selected by the microphone array selection unit 41.
  • the running vehicle detection apparatus 3 is adapted to use the plural wind detection apparatuses 1, 1a, 1b different in wind preventing effect and microphone sensitivity, and to have the ECU 40 detect the running vehicles from among the outputs of the microphone arrays 10, 10a, 10b by using the sound signals of the microphone arrays determined not to catch the wind sound
  • the wind detection apparatus can prevent the influence of the wind as much as possible, and in addition can detect the running vehicles by using the signals of the sounds of the microphone array having an extremely high microphone sensitivity. In other words, the performance of the running vehicle detection is best in the state when the wind hits each microphone 11 or the like.
  • the wind detection apparatus 1, 1a, 1b are applied to a system (the running vehicle detection apparatus, the warning device) to be mounted on a vehicle
  • the wind detection apparatus according to the present invention is not necessarily limited to these structures to be mounted on the vehicle.
  • the wind detection apparatus according to the present invention can be applied for example to a system which can open and close an automatic door to be attached to a building or the like, and may halt the opening and closing actions when the wind speed estimated is equal to or higher than the predetermined level.
  • each of the microphone arrays may be constituted by three or more microphones.
  • the wind detection apparatus has such an advantage that the wind detection apparatus can accurately detect the wind, and is useful for wind detection apparatuses in general for detecting the wind by using the plurality of microphones.
  • the wind detection apparatus according to the present invention is useful when applied to a system that detects vehicles around the own vehicle to catch the sounds of the microphones generated outside of the vehicle to provide a warning to the driver.

Abstract

Provided is a wind detection apparatus which can accurately detect wind. The wind detection apparatus 1 comprises a plurality of microphones 11, 12, a spectrum analyzer unit 22 for acquiring a frequency characteristic representing a sound pressure at each frequency band area from a plurality of sound signals detected by the two microphones 11, 12, a sound pressure/dispersion comparison unit 23 for comparing the acquired frequency characteristics (sound pressure/dispersion) of the two microphones 11, 12, and a wind determination unit 24. The wind determination unit 24 determines in accordance with the comparison results of the sound pressure/dispersion comparison unit 23 that the sounds detected by the two microphones 11, 12 are wind sounds when the difference between the sound pressures of the two microphones 11, 12 is detected throughout the predetermined frequency band areas.

Description

WIND DETECTION APPARATUS
The present invention relates to a wind detection apparatus for detecting wind by using a plurality of microphones.
There have so far been proposed a wide variety of techniques for detecting the wind by using a plurality of microphones. As one example of the techniques, there is a wind noise detection apparatus which comprises a plurality of microphones having substantially the same characteristic and disposed close to each other, to compare the levels of the signals output from the respective microphones and to detect wind noises in response to the difference between the levels of the signals (see for example Patent Document 1).
Further, there is proposed a crosswind warning apparatus which also comprises a plurality of microphones mounted on a vehicle to estimate crosswind around the vehicle from the sounds collected by the microphones outside the vehicle and to calculate the wind power or wind speed, thereby making it possible to warn a driver of the crosswind (see for example Patent Document 2).
Furthermore, there is proposed a vehicle exterior sound detection apparatus which also comprises a plurality of microphones mounted on a vehicle to detect only one detection target sound from the exterior sounds collected by the microphones outside the vehicle (see for example Patent Document 2). This means that the vehicle exterior sound detection apparatus is designed to detect running sounds emitted from the approaching vehicles as vehicle exterior sounds.
Patent Document 1: Japanese Published Unexamined Utility Model Application No. H3-69996
Patent Document 2: Japanese Patent Application Publication No. 2008-254487
Patent Document 3: Japanese Patent Application Publication No. 2011-233090
However, Patent Document 1 only discloses that the wind noise detection apparatus is configured to detect the presence or absence of the wind noises in response to the level difference of the output signals output from the microphones, but does not disclose the particulars about a comparison method of the output signals output from the microphones. For this reason, there is a room to improve for accurately detecting the wind by using a plurality of microphones having substantially the same characteristic and disposed in the vicinity of each other.
Further, the following disadvantages may occur when such a wind detection apparatus is applied to a system for detecting outside running vehicles (other vehicle) surrounding the own vehicle by catching the sounds generated outside of the own vehicle by the microphones as described in Patent Document 3 described above, or otherwise applied to a system that gives a predetermined warning (alert) to the driver when detecting the wind as described in Patent Document 2 described above.
More specifically, there are various kinds of sounds other than running vehicle sound under the real environment. Among other sounds, especially remarkably generated is wind sound. Unless the wind sound can be detected, it is a high possibility that the sound generated when the wind hits the microphone (especially when strong wind is blowing), is erroneously detected as being running vehicle sound. As a consequence, the driver may erroneously be warned despite the sounds of the wind being really not the sounds emitted from the running nearby vehicle, thereby resulting in lowering the reliability as a warning system.
On the other hand, it is known that the above running vehicle sounds generated by the vehicle with tires running on the public roads have a specific frequency characteristic, and have a high sound pressure component in a frequency band area (hereinafter simply referred to as "running sound band are") especially in the range of 800Hz to 3000Hz. In view of the previously mentioned fact, it may be considered to deem the sounds of the frequency outside of the running sound band to be disturbance sounds. For this reason, a suitable filter is used to cut off the frequency outside of the running sound band, thereby preventing an erroneous detection caused by the sounds other than the running vehicle sound.
However, the sounds generated by the wind hitting the microphones frequently include a frequency component in the running sound band in the range of 800Hz to 3000Hz. For this reason, under the condition that the wind cannot be accurately detected, only using such a filter as mentioned in the above cannot satisfactorily prevent the erroneous detection caused by the wind sound.
The present invention has been made to solve the problems of the prior art as described above, and has an object to provide a wind detection apparatus which can accurately detect the wind.
To achieve the above object, the wind detection apparatus according to the present invention (1) comprises a plurality of microphones, a frequency characteristic acquisition unit that acquires frequency characteristics from signals of sounds detected by the plurality of microphones, the frequency characteristics each representing a sound pressure at each of frequency band areas respectively divided at a predetermined frequency interval, a frequency characteristic comparison unit that compares the frequency characteristics of the plurality of microphones acquired by the frequency characteristic acquisition unit, and a wind determination unit that determines that the sounds detected by the plurality of microphones are wind sounds, respectively, when a difference among the sound pressures of the plurality of microphones is detected throughout the frequency band areas excluding a low frequency band area in a range of zero to a predetermined frequency in accordance with comparison results of the frequency characteristic comparison unit.
The wind detection apparatus according to the present invention is adapted to determine that the sounds detected by the plurality of microphones are wind sounds, respectively, when the difference among the sound pressures of the plurality of microphones is detected by the wind determination unit throughout the predetermined frequency band areas, based on the sound pressures in respective frequency band areas of the plurality of microphones acquired by the frequency characteristic acquisition unit.
As will be explained hereinafter in detail, the wind detection apparatus according to the present invention can determine whether or not the sounds detected by the plurality of microphones are respectively caused by the wind by utilizing the fact that there is a remarkable difference seen among the frequency characteristics of the sound pressures acquired when the wind hits the plurality of microphones even if the sound signals detected by the plurality of microphones include frequency components of the sounds such as the running vehicle sounds other than the wind sounds. Therefore, the wind detection apparatus according to the present invention can accurately detect the wind.
The wind detection apparatus as set forth in (1), (2) may further comprise a storage unit that preliminarily stores as a default value data indicating dispersions of the sound pressures in each frequency band area in the frequency characteristics of the plurality of microphones acquired from the signals of the sounds detected by the plurality of microphones in absence of the wind, and in which the wind determination unit determines that the sounds detected by the plurality of microphones are wind sounds, respectively, when the difference among the sound pressures of the plurality of microphones is larger than the default value.
The wind detection apparatus according to the present invention is adapted to have the wind determination unit determine that the sounds detected by the plurality of microphones are wind sounds, respectively, when the difference among the sound pressures of the plurality of microphones is large in comparison with the default value acquired from the signals of the sounds of the plurality of microphones in the absence of the wind. This leads to the fact that the wind detection apparatus according to the present invention can accurately detect the wind as compared with the case in which the difference among the sound pressures of the plurality of microphones is detected throughout the predetermined frequency band area as seen from the above description (1).
In the wind detection apparatus as set forth in (1), (3) the frequency characteristic comparison unit compares dispersions of the sound pressures in the frequency characteristics of the plurality of microphones acquired by the frequency characteristic acquisition unit, and the wind determination unit determines that the sounds detected by the plurality of microphones are wind sounds, respectively, when the dispersion of the sound pressures of the microphone having a high sound pressure is smaller than the dispersion of the sound pressures of the microphone having a low sound pressure, in accordance with comparison results of the frequency characteristic comparison unit.
The wind detection apparatus according to the present invention is adapted to have the wind determination unit determine that the sounds detected by the plurality of microphones are wind sounds, respectively, when the dispersion of the sound pressures having a high sound pressure is smaller than the dispersion of the sound pressures having a low sound pressure.
As will be explained hereinafter in more detail, it can be assumed that when the wind hits the plurality of microphones, the microphone having a high sound pressure is less influenced by the wind and thus has a relatively smaller pressure, so that the microphone having the high sound pressure has a relatively smaller dispersion of sound pressures. Therefore,the wind detection apparatus according to the present invention can detect that the dispersion of the sound pressures of a microphone having a high sound pressure is smaller than the dispersion of the sound pressures of another microphone having a low sound pressure, thereby making it possible to more accurately detect the wind.
The present invention can provide a wind detection apparatus which can accurately detect the wind.
Fig. 1 is a diagram showing frequency characteristics of sounds detected by the two microphones in the absence of wind. Fig. 2 is a diagram showing frequency characteristics of sounds detected by the two microphones hit by the wind. Fig. 3A is a view for explaining sound pressure variations of sound and wind detected by the two microphones. Fig. 3B is a view for explaining sound pressure variations of sound and wind detected by the two microphones. Fig. 4 is a first embodiment of a wind detection apparatus according to the present invention, and a block diagram showing the constitution of the wind detection apparatus. Fig. 5A is a view showing a first embodiment of the wind detection apparatus according to the present invention, and a microphone forming a part of a microphone array constituting a part of the wind detection apparatus and mounted on a vehicle. Fig. 5B is a view showing a first embodiment of the wind detection apparatus according to the present invention, and a microphone forming a part of a microphone array constituting a part of the wind detection apparatus and mounted on a vehicle. Fig. 5C is a view showing a first embodiment of the wind detection apparatus according to the present invention, and a microphone forming a part of a microphone array constituting a part of the wind detection apparatus and mounted on a vehicle. Fig. 6 is a first embodiment of the wind detection apparatus according to the present invention, and a flow chart showing an example of a process relating to the wind detection. Fig. 7 is a first embodiment of the wind detection apparatus according to the present invention, and a flow chart showing another example of the process relating to the wind detection. Fig. 8 is a first embodiment of the wind detection apparatus according to the present invention, and a flow chart showing a further example of the process relating to the wind detection. Fig. 9 is a second embodiment of the wind detection apparatus according to the present invention, and a block diagram showing a schematic constitution of a warning device using the wind detection apparatus. Fig. 10 is a third embodiment of the wind detection apparatus according to the present invention, and a block diagram showing a schematic constitution of the warning device using the wind detection apparatus. Fig. 11A is a third embodiment of the wind detection apparatus according to the present invention, and shows an explanation view of a mesh structure to be mounted on each of the microphones. Fig. 11B is a third embodiment of the wind detection apparatus according to the present invention, and shows an explanation view of a mesh structure to be mounted on each of the microphones. Fig. 11C is a third embodiment of the wind detection apparatus according to the present invention, and shows an explanation view of a mesh structure to be mounted on each of the microphones.
DESCRITION OF EMBODIMENTS
The embodiments of the wind detection apparatus according to the present invention will hereinafter be explained with reference to the drawings.
The wind detection apparatus according to the present invention can be applied to various applications, but the embodiments described below will be explained raising examples to be applied to a system for having microphones respectively catch sounds generated by other surrounding running vehicles (other vehicles) outside of a driver's vehicle (hereinafter simply referred to as "own vehicle" to detect other vehicles, and a system for warning the detection of the other running vehicles to a driver.
(Preliminary Items)
First, in order to better understand the wind detection apparatus according to the present invention, there will be described problems in the current state of the art and how to solve the problems.
Conventionally, there has been developed a system which is adapted to use a generalized cross correction phase transform (hereinafter simply referred to as "GCC-PHAT") method (or called a cross-power spectrum phase analysis (hereinafter simply referred to as "CSP") method) to warn the driver that there are some running vehicles in the vicinity of the own vehicle. The GCC-PHAT method is carried out by two or more microphone arrays in such a manner to calculate the relationship between the correlation values of the sounds and the difference of the arrival times to the two microphones and to detect the directions and the presence or absence of a specific sound source. The warning system adapted to perform the GCC-PHAT method has an arrangement distance of for example 10cm between the two microphones which collectively constitute a microphone array.
On the other hand, the sound produced by a vehicle with tires on a public road has a high sound pressure component in a running sound band area (800Hz ~ 3000Hz) as described above. For this reason, the frequency outside of the running sound band area is generally designed to have the above correlation values of sounds be out of targets to be calculated to prevent the erroneous detection caused by the sounds other than the running vehicle sounds.
However, the running sound band includes a frequency component of the sound other than the running vehicle sound. Especially when the wind hits the microphones, there is a tendency that the sound pressure increases throughout the running sound band. For example, when FIGS. 1 and 2 showing frequency characteristics of the sounds detected by the microphones, respectively are compared, the frequency characteristic of the sound in the presence of the wind hitting the microphone (see FIG. 2 is seen as being increased in the sound pressure throughout the entire frequency band area (0 ~ 12000Hz in an illustrated example) including the running sound band (800Hz ~ 3000Hz) as compared with the frequency characteristic of the sound in absence of the wind (see FIG. 1).
This means that the current technique determines that when the wind hits the microphone, the sound caused by the wind hitting the microphone is deemed to be a running vehicle sound, thereby leading to erroneously detecting the existence of the other running vehicle in the vicinity of the own vehicle. This erroneous detection of the other vehicle leads to giving an unnecessary warning to the driver. It will therefore be understood that the above erroneous detection is one of important problems to be solved.
For this reason, the following explanation will be directed to the wind detection apparatus according to the embodiment of the present invention which is designed to solve the previously mentioned problem. The wind detection apparatus according to the embodiment of the present invention is constructed by utilizing the fact that when the wind hits the microphone, the sound pressure varied for every frequency band area is characteristic., viz., causing a remarkable difference between the frequency characteristics of the sounds detected by the two microphones. The wind detection apparatus according to the embodiment of the present invention thus constructed can determine whether or not the sounds are affected by the wind.
The following explanation will be made about a principle that determines whether or not the sound detected by the microphone is affected by the wind with reference to FIGS. 1 to 3.
FIG. 1 is a diagram showing frequency characteristics acquired by the signals of the sounds detected by the two microphones in the absence of wind. FIG. 2 is a diagram showing frequency characteristics acquired by the signals of the sounds detected by the two microphones hit by the wind. In FIGS. 1 and 2, the horizontal axis represents the frequency (Hz), while the vertical axis represents the sound pressure level (dB). The frequency characteristics shown by the broken line are obtained from one of microphones (microphone 11), while the frequency characteristics shown by the solid line are obtained from the other of microphones (microphone 12).
When the two microphones 11, 12 are disposed at a distance of 10cm, and are attached to the forward end of the body portion of the own vehicle, the frequency characteristics shown in FIGS. 1 and 2 are obtained from the signals of the sound detected by the two microphones 11, 12.
If there is no wind, the sound energies (sound pressures SP1, SP2) caught by the two microphones 11, 12 are substantially the same with each other in the frequency band areas excluding one part of low frequency band areas in the vicinity of zero, thereby allowing both of the frequency characteristics to be matched with each other due to the fact that the two microphones 11, 12 are arranged close to each other, for example, at a distance of 10cm.
In contrast, when the wind hits the two microphones 11, 12, the sound pressure SP1 of one of the microphone 11 is, as shown in FIG. 2, higher in level than the sound pressure SP2 of the other of the microphone 12 throughout the entire frequency band area. This is due to the following reasons.
When the sounds of the sound speed 340m/sec (for example, running sounds from other vehicles running outside of the own vehicle) reach the two microphones 11, 12 from the same sound source at an angle inclined with respect to the two microphones11, 12 as shown in FIG. 3A, there is caused a time difference when the sounds reach the two microphones 11, 12, respectively. Due to the fact that the distance between the two microphones 11, 12, is 10cm, the time difference of the sounds reaching the two microphones 11, 12, is about 0.3msec or less.
When the wind is considered to be blowing at a wind speed of 10m/sec from the direction laterally inclined with respect to the two microphones 11, 12 as shown in FIG. 3B, the wind firstly hits one of the microphone 11, and then hits the other of the microphone 12 after about 10msec elapses. This means that the time difference appearing with the effect of the wind with respect to the two microphones 11, 12, is about 10msec or less.
The sound is a vibration that is alternately generated by the density state of air or wind. The running sound band area is about 800Hz ~ 3000Hz, while the air density vibration generated by the wind is far less, i.e., far slowly than that of the running sound. This means that the mass of air containing the vibration of air of the running sound is in the form of the two microphones 11, 12, hit by the wind, so that the sound pressure of each of the two microphones 11, 12 in the presence of the wind becomes larger in the almost entire frequency band area excluding the extremely small portion of the low frequency band area than that of each of the two microphones 11, 12 in the absence of the wind (see FG. 1 and FIG. 2. This effect is substantially constant regardless of the frequency due to the above reason.
Therefore, the wind with the wind speed 10m/sec influencing the change of the sound pressure of the microphone 11 reaches the microphone 12 spaced apart at a distance of 10cm from the microphone 11 approximately 10msec after the change of the sound pressure of the microphone 11, thereby leading to the fact that at this time, the change of the sound pressure of the microphone 12 is also observed. When the difference of the sound pressures in each of the frequency band areas between the one and the other of the two microphones 11, 12 is observed at the moment when the wind firstly hits the microphone 11, the sound pressure SP1 of the microphone 11 is higher than the sound pressure SP2 of the microphone 12 throughout the entire frequency band area (frequency band area shown by a symbol "WF" in FIG. 2) excluding the low frequency band area in a predetermined range from zero as shown in FIG. 2.
From the foregoing description, it will be understood that the sound pressure difference (sound pressure difference shown by a symbol "Df" in FIG. 2) of the sounds detected by the two microphones 11, 12 in each of the frequency band areas makes it possible to determine whether or not the sounds detected by the two microphones 11, 12 are influenced by the wind.
(First Embodiment)
FIGS. 4 to 8 show a first embodiment of the wind detection apparatus according to the present invention.
First, the constitution of the wind detection apparatus will be explained hereinafter. As shown in FIG. 4, the wind detection apparatus according to the present invention is provided with a microphone array 10, and an Electronic Control Unit (hereinafter simply referred to as an "ECU") 20.
The microphone array 10 comprises a plurality of microphones having substantially the same characteristic (two microphones 11, 12 in this embodiment). The microphones 11, 12 of the microphone array 10 are spaced apart at a distance of 10cm from each other, and thus disposed close to each other in the same arrangement state to catch the sounds respectively reaching the two microphones 11, 12 from the same direction.
In the present embodiment, the wind detection apparatus 1 is mounted on the own vehicle, and the two microphones 11, 12 constituting the microphone array 10 are adapted to detect the sounds generated outside of the own vehicle, the sounds including a wind sound, a running sound generated from other vehicle surrounding the own vehicle and the like. This means that the microphone array 10 is installed at a suitable location on the own vehicle.
For example, the microphone array 10 may be installed on the bumper portion B of the vehicle P as shown in FIG. 5A, or otherwise may be installed in the vicinity of the windshield in the bonnet BN of the vehicle P as shown in FIG. 5B. Further, the microphone array 10 may be installed in the roof carrier R which is provided on the ceiling portion of the vehicle P as shown in FIG. 5C.
Further, the two microphones 11, 12 constituting the microphone array 10 are adapted to output the signals of the sounds outside of the vehicle detected by the two microphones 11, 12, respectively, to the ECU 20.
The ECU 20 is an electronic control unit including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and others, which are not shown in the drawings, to carry out the process according to the wind detection. As shown in FIG. 4, the ECU 20 includes an analog/digital (A/D) converter unit 21, a spectrum analyzer unit 22, a sound pressure/dispersion comparison unit 23, a wind determination unit 24, and a memory unit 25.
The A/D converter unit 21 is illustrated by a functional block for A/D converting the sound signals (analog signals) output from the two microphones 11, 12 into digital signals, respectively. The A/D converter unit 21 is configured to output the A/D converted sound signals to the spectrum analyzer unit 22.
The spectrum analyzer unit 22 is illustrated by a functional block for acquiring the frequency characteristic (spectrum) representing the sound pressure of each frequency band area divided at a predetermined frequency interval, from the sound signals input through the A/D converter unit 21 from the two microphones 11, 12, the frequency characteristic (spectrum) to be acquired is a frequency characteristic as shown in FIG. 2. The spectrum analyzer unit 22 constitutes a frequency characteristic acquisition unit as set forth in the present invention.
More specifically, the spectrum analyzer unit 22 is adapted to divide the two input sound signals of the two microphones 11, 12 into frequency band areas (for example, each having a frequency interval of 100Hz) by using a Fast Fourier Transform (FFT) to calculate the sound pressures of the two microphones 11, 12, in each frequency band area (performing spectral analysis).
If the interval of the frequency band area to be divided is extremely narrow, the adjacent frequencies sometimes swing up and down. To eliminate this effect, the spectrum analyzer unit 22 may, for example, be configured to calculate FFT for every 10Hz. In this case, the spectral analyzer unit 22 may perform the FFT calculation ten times to average the sound pressures acquired by this calculation, thereby allowing the averaged values to be the sound pressures for 100Hz, respectively.
The sound pressure/dispersion comparison unit 23 is illustrated by a functional block for comparing the frequency characteristics (spectrum) of the two microphones 11, 12 obtained by the spectrum analyzer unit 22. The sound pressure/dispersion comparison unit 23 constitutes a frequency characteristic comparison unit as set forth in the present invention.
More specifically, the sound pressure/dispersion comparison unit 23 is adapted to compare the sound pressures at each frequency band area obtained by the spectral analysis for the sound signals of the two microphones 11, 12, and to compare the dispersion of the sound pressures.
The wind determination unit 24 is illustrated by a functional block for determining whether or not the sounds detected by the two microphones 11, 12 are respectively wind sounds based on the comparison results by the sound pressure/dispersion comparison unit 23. The wind determination unit 24 constitutes a wind determination unit as set forth in the present invention.
More specifically, the wind determination unit 24 is adapted to determine that the sounds detected by the two microphones 11, 12 are respectively wind sounds when the difference between the sound pressure SP1 of the microphone 11 and the other sound pressure SP2 of the microphone 12, i.e., the sound pressure difference Df between the two microphones 11, 12, is detected throughout the frequency band area WF, which is constituted by the aforementioned frequency band areas excluding the low frequency band area in the range of zero to the predetermined low frequency, in accordance with the frequency characteristics as shown in FIG. 2.
The reason why the low frequency band area in the range of zero to the predetermined low frequency is excluded from among the frequency band areas which include a detection target of the sound pressure difference will be described hereinafter. The reason is due to the fact that the sound difference Df between the sound pressures of the two microphones 11, 12 sufficiently does not appear in the low frequency band area even if the wind is blowing. The low frequency band area to be excluded from among the detection targets may be in the range of, for example, 0 ~ 1000Hz as shown in FIG. 2.
Further, the wind determination unit 24 is adapted to determine that the microphone 11 catches the wind sound at the moment (see FIG. 3) when the wind firstly strikes the microphone 11, and to detect, at this time, the difference Df (see FIG. 2) between the sound pressures of the two microphones 11, 12. As a specific method for microphone 11 to catch the wind sound, there may be considered several methods which will be described hereinafter.
As a first method, the wind determination unit 24 may determine in accordance with the comparison results by the sound pressure/dispersion comparison unit 23 that the microphone 11 catches the wind sound when the numerical percentage of the frequency band areas in which the sound pressure SP1 of the microphone 11 is higher than the sound pressure SP2 of the microphone 12 I is equal to or more than a predetermined ratio.
As a second method, the wind determination unit 24 may determine in accordance with the comparison results by the sound pressure/dispersion comparison unit 23 that the microphone 11 catches the wind sound when the total value totaling in all of the frequency band areas the differences obtained by reducing the sound pressures SP2 of the microphone 12 from the sound pressures SP1 of the microphone 11 for each of the frequency band areas.
The memory unit 25 is adapted to store the data indicating the dispersion of the sound pressures in each of frequency band areas of the two microphones 11, 12 calculated from the sound signals respectively detected by the two microphones 11, 12 in the absence of the wind, viz., the data of the frequency characteristics as shown in FIG 1 for example as default values. The memory unit 25 constitutes a storage unit as set forth in the present invention.
The wind determination unit 24 is adapted to determine with reference to the data (default values) stored in the memory unit 25 that the sounds respectively detected by the two microphones 11, 12 are wind sounds, respectively, when the difference Df between the sound pressures of the two microphones 11, 12 is larger than the default value.
The wind determination unit 24 is adapted to determine in accordance with the comparison results by the sound pressure/dispersion comparison unit 23 that the sounds respectively detected by the two microphones 11, 12 are wind sounds, respectively, when the dispersion of the sound pressure SP1 of the microphone 11(see FIG. 2) having a high sound pressure is smaller than the dispersion of the sound pressure SP2 of the microphone 12 having a low sound pressure.
The reason why the previous determination can be performed is based on the following description. This reason is due to the fact that the pressure raised by the effect of the wind leads to suppressing the sound from being vibrated. In other words, it can be estimated that the microphone 11 having the high sound pressure is to receive a relatively small pressure generated under the influence of the wind, thereby making it possible to relatively reduce the dispersion (variation amount) of the sound pressure SP1 of the microphone 11.
The memory unit 25 is adapted to store, as a lookup table, the data indicating the relationships between the wind speeds and the differences of the sound pressures of the two microphones 11, 12 in each of frequency band areas of the two microphones 11, 12. The wind speeds and the differences between the sound pressures of the two microphones 11, 12 are preliminarily acquired through repeated experiments. As the data indicating the differences between the sound pressures of the two microphones 11, 12, the average value of the differences between the sound pressures of the two microphones 11, 12 in each of frequency band areas of the two microphones 11, 12 to be obtained through the first method, or otherwise the total value of the differences between the sound pressures of the two microphones 11, 12 to be obtained through the second method is used.
With reference to the data ( a lookup table ) stored in the memory unit 25 , the wind determination unit 24 is adapted to estimate the wind strength (wind speed) in accordance with the average value or the total value of the difference between the sound pressures of the two microphones 11, 12. The reason why the wind determination unit 24 can estimate the wind strength (wind speed) is due to the fact that the stronger the wind is (the higher the wind speed is), the above difference between the sound pressures is increased.
Next, the wind detection process to be carried out by the wind detection unit ECU 20 in the wind detection apparatus 1 according to the present embodiment will be explained hereinafter.
FIG 6 is a flowchart showing an example of the process relating to the wind detection. As shown in FIG 6, the ECU 20 is input with the sound signals respectively detected by the two microphones 11, 12 (Step S1). The sound signals (analog signals) input into the ECU 20 is converted into digital signals, respectively, through the A/D converter unit 21, and then input into the spectrum analyzer unit 22.
The spectrum analyzer unit 22 then divides the input sound signals (digital signals) of the two microphones 11, 12 for example into a plurality of frequency band areas of 100Hz each by using the Fast Fourier Transform (FFT) (Step S2), and to calculate the sound pressure for every frequency band area of each of the two microphones 11, 12 (Step S3). The wind detection apparatus therefore can acquire the frequency characteristics (spectrum) as shown in FIG. 2.
The sound pressure/dispersion comparison unit 23 then compares the sound pressures of the two microphones 11, 12 in each of the frequency band areas in the frequency characteristics (spectrum) acquired by the spectrum analyzer unit 22 (Step S4).
The wind determination unit 24 then determines whether or not the difference Df between the sound pressures (see FIG. 2) of the two microphones 11, 12 is detected throughout the frequency band area WF, which is constituted by the plurality of said divided frequency band areas excluding the low frequency band area in the range of zero to the predetermined low frequency, in accordance with the comparison results obtained by the sound pressure/dispersion comparison unit 23 (Step S5).
When the wind determination unit 24 determines that the difference Df between the sound pressures of the two microphones 11, 12 is detected throughout the frequency band area WF ("YES" in Step S5), the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are caused by the wind to output the signal indicative of the determination results showing that the sounds are caused by the wind (Step S6). The above process of the wind detection apparatus is repeated thereafter.
When, on the other hand, the wind determination unit 24 determines that the difference Df between the sound pressures of the two microphones 11, 12 is not detected throughout the frequency band area WF ("NO" in Step S5), the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are not caused by the wind to output the signal indicative of the determination results showing that the sounds are not caused by the wind. The above process of the wind detection apparatus is repeated thereafter.
FIG 7 is a flowchart showing another example of the process relating to the wind detection to be carried out by the wind detection apparatus according to the present invention. The process flow shown by this flow chart is assumed to show a case in which the determination results in the Step 5 is "YES" in the flow chart shown in FIG. 6 (viz., a case in which the difference between the sound pressures of the two microphones 11, 12 is detected over the predetermined frequency band area).
Under the assumption condition as previously mentioned, the wind determination unit 24 in the ECU 20 reads out from the memory unit 25 the default value preliminarily obtained, viz., the data indicating the dispersion of the sound pressures of the two microphones 11, 12 in the absence of the wind (Step S11).
The wind determination unit 24 then determines whether or not the difference Df between the sound pressures (see FIG. 2) of the two microphones 11, 12 in accordance with the comparison results by the sound pressure/dispersion comparison unit 23 is larger than the default value read out from the memory unit 25 (Step S12).
When the difference Df between the sound pressures of the two microphones 11, 12 is equal to and larger than the default value ("YES" in Step 12), the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are caused by the wind (Step S13) to output the signal indicative of the determination results showing that the sounds are caused by the wind. The above process of the wind detection apparatus is repeated thereafter.
When, on the other hand, the difference Df between the sound pressures of the two microphones 11, 12 is equal to and smaller than the default value ("NO" in Step 12), the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are not caused by the wind to output the signal indicative of the determination results showing that the sounds are not caused by the wind. The above process of the wind detection apparatus is repeated thereafter.
FIG 8 is a flowchart showing a further example of the process relating to the wind detection to be carried out by the wind detection apparatus according to the present invention. The process flow shown by this flow chart is assumed to show a case in which the determination result in the Step 5 is "YES" in the flow chart shown in FIG. 6 (viz., a case in which the difference between the sound pressures of the two microphones 11, 12 is detected over the predetermined frequency band area).
Under the assumption condition as previously mentioned, the sound pressure/dispersion comparison unit 23 in the ECU 20 compares the dispersions of the sound pressures of the two microphones 11, 12 for each of the frequency band areas in accordance with the frequency characteristics obtained by the spectrum analyzer unit 22 (spectrum) (Step S21).
The wind determination unit 24 then determines in accordance with the comparison results obtained by the sound pressure/dispersion comparison unit 23 whether or not the dispersion of the sound pressure SP1 of the microphone 11 (see FIG. 2) having a high sound pressure is smaller than the dispersion of the sound pressure SP2 of the microphone 12 having a low sound pressure (Step S22).
When the dispersion of the sound pressure SP1 of the microphone 11 (see FIG. 2) having the high sound pressure is smaller than the dispersion of the sound pressure SP2 of the microphone 12 having the low sound pressure ("YES" in Step S22), the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are caused by the wind to output the signal indicative of the determination results showing that the sounds are caused by the wind (Step S23). The above process of the wind detection apparatus is repeated thereafter.
When, on the other hand, the dispersion of the sound pressure SP1 of the microphone 11 (see FIG. 2) having the high sound pressure is equal to and higher than the dispersion of the sound pressure SP2 of the microphone 12 having the low sound pressure ("NO" in Step 22), the wind determination unit 24 determines that the sounds respectively caught by the two microphones 11, 12 are not caused by the wind to output the signal indicative of the determination results showing that the sounds are not caused by the wind. The above process of the wind detection apparatus is repeated thereafter.
From the foregoing description, it will be understood that the wind detection apparatus 1 according to the present embodiment is configured to have the wind determination unit 24 in the ECU 20 determine that the sounds respectively detected by the two microphones 11, 12 are caused by the wind when the difference Df between the sound pressure of the microphone 11 and the sound pressure of the microphone 12 is detected throughout the predetermined frequency band area WF from among the sound pressures of the two microphones 11, 12 in each of the frequency band areas analyzed by the spectrum analyzer unit 22 (frequency characteristics shown in FIG. 2).
More specifically, the wind detection apparatus 1 according to the present embodiment can determine whether or not the sounds detected by the two microphones 11, 12 are respectively caused by the wind by utilizing the fact that there is a remarkable difference seen between the frequency characteristics of the sound pressures SP1, SP2 acquired when the wind hits the two microphones 11, 12 as shown in FIG. 2 even if the sound signals detected by the two microphones 11, 12 include frequency components of the sounds such as the running vehicle sounds other than the wind sounds as previously mentioned. Therefore, the wind detection apparatus 1 according to the present embodiment can more accurately detect the wind.
Further, the wind detection apparatus 1 according to the present embodiment is configured to determine that the sounds detected by the two microphones 11, 12 are respectively caused by the wind when the difference Df between the sound pressures of the two microphones 11, 12 (see FIG. 2) is large as compared with the default value (frequency characteristic shown in FIG. 1) acquired from the sound signals of the two microphones 11, 12 in the absence of the wind. This leads to the fact that the wind detection apparatus 1 according to the present embodiment can more accurately detect the wind as compared with the case in which the difference Df between the sound pressures of the two microphones 11, 12 is detected throughout the predetermined frequency band area WF.
Further, the wind detection apparatus 1 according to the present embodiment is configured to determine that the sounds detected by the two microphones 11, 12 are respectively caused by the wind when the ECU 20 detects the fact that the dispersion of the sound pressure SP1 of the microphone 11 (see FIG. 2) having the high sound pressure is smaller than the dispersion of the sound pressure SP2 of the microphone 12 having the low sound pressure.
When the wind hits the two microphones 11, 12, the microphone 11 having the high sound pressure is influenced by the wind and thus have a relatively small pressure,so that the dispersion of the sound pressure SP1 of the microphone 11 is estimated to be relatively reduced, so that the wind detection apparatus 1 according to the present embodiment can detect the fact that the dispersion of the sound pressure SP1 of the microphone 11 having the high sound pressure becomes smaller than the dispersion of the sound pressure SP2 of the microphone 12 having the low sound pressure.
(Second Embodiment)
FIG. 9 shows a second embodiment of the wind detection apparatus according to the present invention. The second embodiment of the wind detection apparatus is partly constituted by a warning device which is operative together with the wind detection apparatus according to the first embodiment previously mentioned.
As shown in FIG. 9, the warning device 2 according to the present embodiment is provided with the wind detection apparatus 1 according to the first embodiment previously mentioned, an ECU 30, and a display unit 35.
The microphones 11, 12 in a microphone array 10 constituting a part of the wind detection apparatus 1 is adapted to output the vehicle outside sound signals respectively detected by the two microphones 11, 12 not only to the ECU 30 but also to the ECU 20 (see FIG. 4) of the wind detection apparatus 1.
Similarly to the ECU 20, the ECU 30 is an electronic control unit which includes a CPU, a ROM, a RAM, and others. The ECU 30 includes an analog/digital (A/D) conversion unit 31, a running vehicle detection unit 32, and a warning mode control unit 33.
The A/D conversion unit 31 is illustrated by a functional block for A/D converting the sound signals (analog signals) output from the two microphones 11, 12 into the digital signals, respectively. Further, the A/D conversion unit 31 is adapted to output the sound signals A/D converted to the running vehicle detection unit 32.
The running vehicle detection unit 32 is illustrated by a functional block for detecting running vehicles (other vehicles) around the own vehicle from the sound signals input through the A/D conversion unit 31 from the two microphones 11, 12. When the running vehicle detection unit 32 detects the running vehicles, the running vehicle detection unit 32 is adapted to output the detection information in response to the detection modes.
The warning mode control unit 33 is illustrated by a functional block for controlling the process to issue warnings (alert) to the driver in accordance with the detection information output from the running vehicle detection unit 32, and the wind determination results output from the wind detection apparatus 1. The warning mode control unit 33 is adapted to output a control signal indicative of the warning to the display unit 35.
More specifically, the warning mode control unit 33 is adapted to output a control signal for performing the predetermined alert when the running vehicle is detected by the running vehicle detection unit 32, and further to output a control signal for changing the alert modes, viz., one alert mode to the other alert mode when the wind is detected by the wind detection apparatus 1.
The display unit 35 includes a monitor or the like for performing an alarm display, and a speaker for outputting sound. When the running vehicle is detected by the running vehicle detection unit 32 in the ECU 30, the display unit 35 outputs the information prompting the warning to the driver through the speaker, or otherwise displays on the monitor in accordance with the control signal output from the warning mode control unit 33. In this case, the display unit 35 may audio output a message, for example, "the running vehicle approaching", or otherwise may display on the monitor.
Further, when the wind is detected by the wind detection apparatus 1, the display unit 35 is adapted to change the output of the alert or the display mode in accordance with the control signal output from the warning mode control unit 33. In this case, the display unit 35 may audio output a message, for example, " the strong wind makes it for the warning system to be under no operation", or otherwise may display information to this effect on the monitor, thereby stopping the alert to the driver.
Further, as a condition for changing the output of the warning or the display mode, the present invention does not necessarily limit the case in which it is determined that the sounds caught by the microphones 11, 12 are caused by the wind, but may include a case in which the wind speed estimated by the wind determination unit 24 (see FIG. 4) is equal to or faster than a predetermined speed.
Further, as the mode for changing the alert, the present invention does not limit the case in which any alert as previously mentioned is not performed, but may include a case in which the intensity of the alert (for example, volume of the warning sound) in response to the estimated wind is varied. More specifically, the present invention may make stronger the intensity of the alert by determining that the running vehicle detection is not sufficiently affected by the wind if the wind speed is low. On the contrary, the present invention may make weaker the intensity of the alert by regarding the confidence of the running vehicle detection as being low due to the fact that the running vehicle detection is strongly affected by the wind if the wind speed is high.
From the foregoing description, it will be understood that the warning device 2 using the wind detection apparatus 1 according to the present embodiment is adapted to perform the predetermined alert when the wind detection apparatus 1 detects the running vehicles around the own vehicle, and further to change the alert modes when the wind detection apparatus 1 detects the wind in accordance with the information of sounds outside of the own vehicle collected by the ECU 30 using the microphone array 10, i.e., the two microphones 11, 12.
From the above reason, the wind detection apparatus according to the present invention can reduce unnecessary alerts to the driver, and can solve such a problem as giving an erroneous alert to the driver despite the sound which is not the running vehicle sound as seen in the state of the art. This contributes greatly to the improvement of the reliability of the warning device 2.
(Third Embodiment)
FIGS. 10 and FIG. 11 show a third embodiment of the wind detection apparatus according to the present invention. The third embodiment of the wind detection apparatus is partly constituted by a running vehicle detection apparatus, using the wind detection apparatus according to the first embodiment previously mentioned.
As shown in FIG. 10 , the running vehicle detection apparatus 3 according to the present embodiment is provided with a plurality of wind detection apparatuses (in the illustrated example, three wind detection apparatuses 1, 1a and 1b), and an ECU 40. The three wind detection apparatuses 1, 1a and 1b respectively include a microphone array 10 (two microphones 11, 12), a microphone array 10a (two microphones 11a, 12a), and a microphone array 10b (two microphones 11b, 12b) which are respectively different in wind preventing effect from one another.
As shown in FIG. 11A, the wind preventing effects to be performed by the microphone array 10, the microphone array 10a, and the microphone array 10b, respectively, can be realized by attaching mesh-like structures (hereinafter simply referred to as "mesh structures") 13 on the front surfaces of the vibration plates of the two microphones 11, 12, 11 a, 12a, 11b, 12b. The mesh structure 13 thus attached can suppress the two microphones 11, 12, 11 a, 12a, 11b, 12b (hereinafter simply referred to as "each microphone 11 or the like") from catching the wind sound, however, gives rise to lowering reducing the energy of sound to be input to each microphone 11 or the like, thereby simultaneously causing the sensitivity of each microphone 11 or the like to be reduced.
The present embodiment is configured to make different the wind preventing effects and the sensitivities for the microphone arrays 10, 10 a, 10b, by preparing a plurality of mesh structures 13 different in mesh roughness, and attaching each of the mesh structures 13 to each microphone 11 or the like. More specifically, the mesh structures 13a relatively coarse in mesh roughness, and the mesh structures 13b relatively fine in mesh roughness are used as shown in FIG. 11B and FIG. 11C.
In the examples shown in FIG. 11B and FIG. 11C, only two kinds of mesh structures 13a, 13b are shown, however, three or more kinds of mesh structures 13 can be prepared by varying the degree of the mesh roughness.
The mesh structure 13a relatively coarse in mesh roughness to be used can reduce the wind preventing effect, but can reduce the microphone sensitivity to a smaller level. This means that the microphone array (for example, microphone array 10) using the mesh structure 13a relatively coarse in mesh roughness can catch the wind sound even with the weaker wind.
If, on the other hand, the mesh structure 13b relatively fine in mesh roughness is used, the wind preventing effect can be heightened, however, the microphone sensitivity is greatly reduced. This means that the microphone array (for example microphone array 10a) using the mesh structure 13a relatively fine in mesh roughness cannot catch the wind sound without the strong wind.
As shown in FIG 10, the two microphones 11, 12, 11a, 12a, 11b 12b in the microphone arrays 10, 10a, 10b partly constituting the wind detection apparatus 1, 1a, 1b are adapted to output the respective signals indicative of the detected sounds outside of the vehicle to the ECU 40 through the signal line 14 (see FIG. 11A).
Similarly to the ECU 20 and the ECU 30, the ECU 40 is an electronic control unit including a CPU, a ROM, a RAM, and others. The ECU 40 includes a microphone array selection unit 41, and a running vehicle detection unit 42.
The microphone array selection unit 41 is illustrated by a functional block for A/D converting into digital signals the sound signals (analog signals) of the two microphones 11, 12, 11a, 12a, 11b, 12b, respectively, output from the microphone arrays 10, 10a, 10b, and for thereafter selecting the outputs of the microphone arrays 10, 10 a, 10b to be used for the running vehicle detection.
More specifically, the microphone array selection unit 41 is adapted to determine whether the microphone arrays 10, 10 a, 10b catch or do not catch the wind sounds in an ascending order of wind preventing effect (in a descending order of microphone sensitivity) in accordance with the sound signals respectively output from the microphone arrays 10, 10 a, 10b.
Furthermore, the microphone array selection unit 41 is adapted to search the microphone having a larger wind preventing effect (lower microphone sensitivity) and to select the microphone array determined not to catch the wind sound, viz., to select the output of the microphone array to use the running vehicle detection when the wind sound is determined to be caught.
The running vehicle detection unit 42 is illustrated by a functional block for detecting vehicles (other vehicles) around the own vehicle by using the output (sound signals) of the microphone array selected by the microphone array selection unit 41.
From the foregoing description, it will be understood that the running vehicle detection apparatus 3 is adapted to use the plural wind detection apparatuses 1, 1a, 1b different in wind preventing effect and microphone sensitivity, and to have the ECU 40 detect the running vehicles from among the outputs of the microphone arrays 10, 10a, 10b by using the sound signals of the microphone arrays determined not to catch the wind sound
As a consequence, the wind detection apparatus according to the present invention can prevent the influence of the wind as much as possible, and in addition can detect the running vehicles by using the signals of the sounds of the microphone array having an extremely high microphone sensitivity. In other words, the performance of the running vehicle detection is best in the state when the wind hits each microphone 11 or the like.
Although the embodiments previously mentioned have been explained raising the cases in which the wind detection apparatus 1, 1a, 1b are applied to a system (the running vehicle detection apparatus, the warning device) to be mounted on a vehicle, the wind detection apparatus according to the present invention is not necessarily limited to these structures to be mounted on the vehicle. The wind detection apparatus according to the present invention can be applied for example to a system which can open and close an automatic door to be attached to a building or the like, and may halt the opening and closing actions when the wind speed estimated is equal to or higher than the predetermined level.
Although the previously mentioned embodiments have been explained about the cases in which the microphone arrays 10, 10a, 10b are respectively constituted by the two microphones 11, 12; 11a, 12a; 11b, 12b, the wind detection apparatus according to the present invention is not limited to the cases, each of the microphone arrays may be constituted by three or more microphones.
It will be understood from the foregoing description that the wind detection apparatus according to the present invention has such an advantage that the wind detection apparatus can accurately detect the wind, and is useful for wind detection apparatuses in general for detecting the wind by using the plurality of microphones. In particular, the wind detection apparatus according to the present invention is useful when applied to a system that detects vehicles around the own vehicle to catch the sounds of the microphones generated outside of the vehicle to provide a warning to the driver.
EXPLANATION OF REFERENCE NUMERALS
1, 1a, 1b ... wind detection apparatus
2 ... warning device
3 ... running vehicle detection apparatus
10,10 a, 10b ... microphone array
11, 12, 11 a, 12a, 11b, 12b ... microphone
13, 13 a, 13b ... mesh structure
22 ... spectrum analyzer unit (frequency characteristic acquiring unit)
23 ... sound pressure/dispersion comparison unit (frequency characteristic comparison unit)
24 ... wind determination unit
25 ... memory unit (storage unit)
32 ... running vehicle detection unit
33 ... warning mode control unit
35 ... display unit
41 ... microphone array selection unit
42 ... running vehicle detection unit
Df ... difference between the sound pressures
P ... vehicle
SP1, SP2 ... sound pressure
WF ... frequency band area excluding the low frequency band area in the range from zero to the predetermined frequency

Claims (3)

  1. A wind detection apparatus comprising:
    a plurality of microphones,
    a frequency characteristic acquisition unit that acquires frequency characteristics from signals of sounds detected by the plurality of microphones, the frequency characteristics each representing a sound pressure at each of frequency band areas respectively divided at a predetermined frequency interval,
    a frequency characteristic comparison unit that compares the frequency characteristics of the plurality of microphones acquired by the frequency characteristic acquisition unit, and
    a wind determination unit that determines that the sounds detected by the plurality of microphones are wind sounds, respectively, when a difference among the sound pressures of the plurality of microphones is detected throughout the frequency band areas excluding a low frequency band area in a range of zero to a predetermined frequency in accordance with comparison results of the frequency characteristic comparison unit.
  2. The wind detection apparatus as set forth in claim 1, which further comprises a storage unit that preliminarily stores as a default value data indicating dispersions of the sound pressures in each frequency band area in the frequency characteristics of the plurality of microphones acquired from the signals of the sounds detected by the plurality of microphones in absence of the wind, and in which the wind determination unit determines that the sounds detected by the plurality of microphones are wind sounds, respectively, when the difference among the sound pressures of the plurality of microphones is larger than the default value.
  3. The wind detection apparatus as set forth in claim 1, in which
    the frequency characteristic comparison unit compares dispersions of the sound pressures in the frequency characteristics of the plurality of microphones acquired by the frequency characteristic acquisition unit, and the wind determination unit determines that the sounds detected by the plurality of microphones are wind sounds, respectively, when the dispersion of the sound pressures of the microphone having a high sound pressure is smaller than the dispersion of the sound pressures of the microphone having a low sound pressure, in accordance with comparison results of the frequency characteristic comparison unit.
PCT/JP2014/004815 2013-10-24 2014-09-18 Wind detection apparatus WO2015059866A1 (en)

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