JP2013242232A - Object approaching surveillance device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device that can broaden a surveillance range and allows a simpler structure to notify a person of an object approach by a position of sound source.SOLUTION: A surveillance device includes: a plurality of pairs of reception antennas that is disposed at a plurality of positions different in the surveillance range; a phase difference signal detector that is provided for each reception antenna of each pair thereof and detects a phase difference signal of a first reception signal received by a first reception antenna and a second reception signal received by a second antenna; and a sound signal generator that generates a sound signal of intensity corresponding to amplitude of each phase difference signal detected by the phase difference signal detector. On the basis of each installation position for each reception antenna of each pair thereof, each right ear head transfer function and each left ear head transfer function serving as respective transfer functions between a right ear of the human being and a left ear thereof and each sound signal output by the sound signal generator, a pseudo sound signal is generated that is a sound signal making the right ear of the human being and the left ear thereof sensed such that each sound source of each sound signal exists at each installation position of the reception antennas and a sound output is performed to the right ear of the human being and the left ear thereof.

Description

The present invention relates to a monitoring device that notifies a person of an approach of an animal or an object such as a human to a monitoring range around a human or a moving body such as a vehicle as a sound.
When used in a vehicle, it is possible to provide a device that makes the driver feel the direction and speed of approach of a monitored object such as a person, a bicycle, or a vehicle around the traveling vehicle as the movement of the virtual sound source. Thereby, the safety device which prevents the interference between the vehicle and the monitoring object can be realized. In addition, when this apparatus is used for a human, it can be used as an auxiliary apparatus for visual acuity that can recognize the approach of a monitored object as a movement of a virtual sound source for a person who has temporarily suffered visual impairment.

  2. Description of the Related Art Conventionally, there is known an apparatus in which ultrasonic sensors are provided at four corners of a vehicle and the surroundings of the four corners of the vehicle are monitored by the ultrasonic sensors. In this apparatus, regarding the approach of the vehicle to the object, the approaching location is indicated by an image, the degree of approach is indicated by a periodic sound, and the danger is notified to the driver by shortening the period of the sound immediately before the interference. There is also known an apparatus that detects the periphery of a vehicle with an image sensor and displays the positions of surrounding objects in a top view together with the vehicle.

  Further, as in Patent Document 1 below, obstacle sensors by radar are provided at the four corners of the vehicle, the direction in which the obstacle exists is determined from the outputs of these sensors, and the sensors are provided at a plurality of locations inside the vehicle. There is known an alarm device that outputs sound from each speaker so that a sound source is present in the direction in which an obstacle exists from the other speaker.

Japanese Patent Laid-Open No. 5-58219

  When an ultrasonic sensor is used for the monitoring device, there is a problem that the monitoring range of the obstacle is narrow. When the direction of the obstacle is shown in the image, the driver needs to change the line of sight from the front or the direction to be watched in the direction of the image, which is bothersome and the direction in which the actual obstacle exists. If the line of sight is delayed, there is a problem that it is difficult to avoid interference with an obstacle.

Further, in the case of Patent Document 1, the position of the obstacle is audibly determined by setting the virtual sound source in the direction in which the obstacle exists by the sound output from a plurality of speakers. To inform. Therefore, there is an advantage that the driver does not need to change the line of sight, and the driver does not hinder driving of the vehicle.
However, in the method of Patent Document 1, it is necessary to calculate the direction in which an obstacle exists from detection signals from a plurality of sensors, and the audio signal to be output to each speaker so as to have a sound source in the specified direction. Need to be generated. For this reason, there has been a problem that the apparatus becomes complicated.
An object of the present invention is to realize a device that can widen the monitoring range and can notify a person of the approach of an object to the person by the position of a sound source with a simpler configuration.

  The present invention relates to a monitoring device that notifies a person of an approach of an object in a monitoring range around the human by sound, and an exciter that outputs an electromagnetic wave to the monitoring range and the electromagnetic wave output by the exciter are arranged at predetermined intervals. The first receiving antenna and the second receiving antenna are set as one set, and each set of antennas is provided for each set of receiving antennas and a plurality of receiving antennas arranged at a plurality of positions having different monitoring ranges. A phase difference signal detector for detecting a phase difference signal between the first reception signal received by the first reception antenna and the second reception signal received by the second antenna, and detected by the phase difference signal detector An audio signal generator that generates an audio signal having an intensity corresponding to the amplitude of each phase difference signal, and each installation function for each set of receiving antennas and each right ear that is a transfer function between the human right and left ears Head Based on the function and each left ear head transfer function and each sound signal output from the sound signal generator, so that the sound source of each sound signal exists at each installation position of the receiving antenna. A pseudo sound signal generating device that generates a pseudo sound signal that is a sound signal to be sensed by the left ear, and a sound output device that outputs the signal output from the pseudo sound signal generating device to the human right and left ears as sound And a monitoring device characterized by comprising:

  An exciter is a device that forms an electromagnetic field by electromagnetic waves in a monitoring range. The monitoring range is the space around the person when the device is installed on the person. When this device is installed in a vehicle, the space around the outside of the vehicle becomes the monitoring range. Although the frequency of electromagnetic waves is arbitrary, for example, 2.4 GHz is used. Sine waves and cosine waves are used as electromagnetic waves.

  When used in a vehicle, the main body of the exciter is provided inside the vehicle and the body is excited by attaching a transmission electrode to the body of the vehicle, or an arbitrary number of transmission antennas are provided outside the vehicle. Electromagnetic waves may be radiated to the monitoring range along the four sides.

  The receiving antenna is an antenna having a set of a first receiving antenna and a second receiving antenna separated by a predetermined interval, for example, about 5 cm. The number of sets is arbitrary as long as it is plural. In order to specify the orientation on the opened surface, it is sufficient to have at least two sets of receiving antennas. When monitoring the periphery of the vehicle, each set of receiving antennas may be provided at the four corners of the vehicle, or may be provided at the center of each of the four sides of the vehicle. The phase difference detector is a device that detects a phase difference between the first received signal and the second received signal, and a phase difference signal is obtained by mixing both signals. When a person, bicycle, car, or other object (hereinafter referred to as “monitoring object”) approaches the monitoring range, the electromagnetic wave environment in the monitoring range is disturbed. That is, an electromagnetic multipath environment is generated. As a result, the phases of the first received signal received by the first receiving antenna and the second received signal received by the second receiving antenna change temporally. Thereby, the phase difference signal becomes a low frequency signal whose frequency changes with time. Further, the amplitude of the phase difference signal increases as the monitored object approaches the first receiving antenna and the second receiving antenna, and the frequency of the phase difference signal increases in proportion to the approaching speed of the monitored object. The present invention uses this phenomenon.

The audio signal generator is a device that generates a virtual sound source. An audio signal having a component of a predetermined frequency band or a white noise component can be used. An audio signal generator can be obtained by amplifying the output of the sound source with a variable gain amplifier.
Each left ear head transfer function and each right ear head transfer function are measured in advance with respect to the installation position of each set of receiving antennas. When each set of receiving antennas is provided at four corners of the vehicle, there are four left ear head transfer functions and four right ear head transfer functions.

  The pseudo audio signal generation device is a device that generates a virtual sound source in real time in the direction in which the monitoring object exists by moving the position of the virtual sound source in accordance with the movement of the monitoring object. A virtual sound source recognized by human hearing is generated by generating a pseudo audio signal that is output to a bone conduction device that directly excites headphones, earphones, or ear shells, or a pseudo audio signal that is output to a speaker. The

  The sound output device can use headphones, earphones, and bone conduction devices that directly excite the ear shells, which directly give sound to the right and left ears of humans, and a plurality of surrounding human beings. A speaker arranged at the position can be used.

  In the present invention, it is desirable that the audio signal generator generates an audio signal having a frequency corresponding to the frequency of each phase difference signal and an intensity corresponding to the amplitude of each phase difference signal. As a result, the approach speed of the monitoring object can be made to be perceived by a human by setting the approach speed of the monitored object to be higher as the sound level is higher, for example, the higher the approach speed.

In the present invention, the pseudo audio signal generation device generates a right ear pseudo audio signal for the right ear by combining each signal obtained based on each audio signal and each right ear head transfer function, and each audio signal and each This is a device for generating a left ear pseudo audio signal for the left ear by synthesizing each signal obtained based on the left ear head transfer function, and the audio output device inputs the right ear pseudo audio signal, It can be set as the apparatus which outputs a sound to a right ear, inputs a left ear pseudo sound signal, and outputs a sound to a human left ear, respectively.
With the right ear pseudo audio signal and the left ear pseudo audio signal, a human can feel as if the virtual sound source exists at the position of the monitored object.

  The method for generating the right ear pseudo speech signal can be obtained in real time by the inverse Fourier transform of the synthesis of each product of the Fourier transform of each speech signal and each right ear head transfer function. Similarly, the method for generating the left ear pseudo audio signal is to calculate the product of each product of the Fourier transform of each audio signal and each left ear head transfer function in real time, and to perform the inverse Fourier transform on the synthesis. Can be sought.

The pseudo audio signal generation device generates a right ear pseudo audio signal for the right ear by combining each signal obtained by convolution integration of each audio signal and each impulse response of each right ear head transfer function. It is good also as an apparatus which produces | generates the left ear pseudo audio | voice signal with respect to a left ear by the synthesis | combination of each signal obtained based on each signal and each impulse response of each left ear head transfer function.
This method is a method of obtaining a pseudo audio signal on the time axis without using Fourier transform and inverse Fourier transform. As a device, each impulse response is stored in a storage device, and a transversal filter is configured using this characteristic as a tap coefficient, so that real-time convolution integration can be executed.

The audio output device is a speaker disposed at each of a plurality of locations around a human. The pseudo audio signal generation device includes each first transfer function between each speaker and the right ear, and between each speaker and the left ear. Each installation position for each receiving antenna and each third transfer function between the speakers determined based on each second transfer function, each right ear head transfer function, and each left ear head transfer function, It can be set as the apparatus which produces | generates the pseudo audio | voice signal which should be output to each speaker by the synthesis | combination of each signal obtained based on each audio | voice signal.
In this device, a pseudo sound source is generated at the position where a monitoring object is present in the human sense of hearing by the sound output of a plurality of speakers arranged around the human. Each third transfer function is based on each pseudo audio signal, and the sound output from each speaker reaches the right ear and the sound when the left ear reaches the right ear. This is a transfer function that is defined to be equivalent to a voice that is transfer-synthesized by the partial transfer function and each left ear-head transfer function.

A method for generating each pseudo audio signal to be output to each speaker is to calculate, in real time, a Fourier transform of each audio signal and a synthesis of each product of each third transfer function for that speaker for one speaker, The synthesis can be obtained by inverse Fourier transform.
In addition, when using a speaker, the pseudo audio signal generating device outputs a pseudo audio signal to be output to each speaker by combining each signal obtained by convolution integration of each audio signal and each impulse response of each third transfer function. It can be set as the apparatus which produces | generates. In this case, each impulse response of each third transfer function is stored in the storage device. Then, by constructing a transversal filter using the impulse response characteristics as tap coefficients, real-time convolution integration can be executed.

  In the present invention, the position of the monitored object can be detected as the position of the pseudo sound source that is detected by human hearing. The movement of the monitoring object can be detected as the movement of the pseudo sound source in the auditory dimension. Further, when a monitored object is closer to a person or vehicle having this apparatus, the sound of the pseudo sound source becomes stronger, and the degree of the approach distance can be detected. Further, the approaching speed of the monitored object can be detected by the level of sound from the pseudo sound source. For example, as the approach speed increases, the pitch increases. Further, in the present invention, a pseudo audio signal can be obtained in real time only by storing each right ear head transfer function and each impulse response thereof, each left ear head transfer function and each impulse response thereof. The configuration of the apparatus is extremely simple.

1 is a configuration diagram of a monitoring device according to Embodiment 1. FIG. The block diagram of an exciter. Explanatory drawing which showed the relationship between the monitoring range of a vehicle periphery, a receiving antenna group, and the installation position of a transmitting antenna. 1 is a configuration diagram of a phase difference detector according to Embodiment 1. FIG. The block diagram of the audio | voice signal generator of Example 1, and a pseudo | simulation audio | voice signal generation apparatus. The block diagram which showed the detail of the audio | voice signal generator of Example 1. FIG. 1 is a configuration diagram of a convolution integrator according to Embodiment 1. FIG. FIG. 6 is a configuration diagram of a monitoring device according to a third embodiment. FIG. 4 is a waveform diagram of each phase difference signal detected by the monitoring apparatus according to the first embodiment. The enlarged waveform figure of the one phase difference signal detected with the monitoring device of Example 1 when a person walks around the vehicle. The enlarged waveform figure of the one phase difference signal detected by the monitoring device of Example 1 when a person runs around the vehicle.

  Hereinafter, the present invention will be described based on specific examples. The present invention is not limited to the following examples.

In the present embodiment, the monitoring object is monitored in the auditory space of the driver by moving the virtual sound source in accordance with the movement of the monitoring object with respect to the driver of the vehicle with a certain width along the four rectangular sides of the vehicle as the monitoring range. This is a device that informs the presence of the device.
FIG. 1 is a diagram illustrating the configuration of the monitoring apparatus according to the first embodiment. The monitoring apparatus according to the first embodiment includes an exciter 1, four reception antenna sets 20, a phase difference detector 2, an audio signal generator 3, a pseudo audio signal generation apparatus 4, and an audio output apparatus 5. I have.

  FIG. 2 is a diagram showing the configuration of the exciter 1. The exciter 1 includes an oscillator 10 and a transmission antenna group 13 connected to the oscillator 10 via a band pass filter 11. The band pass filter 11 transmits only the frequency band of the electric signal oscillated by the oscillator 10. This band pass filter 11 is not always necessary, but it is desirable to provide this filter in order to remove noise and improve the sensitivity of the monitoring apparatus of the first embodiment. An electric signal from the band pass filter 11 is radiated into the space as an electromagnetic wave from the transmitting antenna group 13.

As shown in FIG. 3, let the corners of the outer periphery of the rectangle of the vehicle 300 be A, B, C, and D. A first receiving antenna set AT ₁ , a second receiving antenna set AT ₂ , a third receiving antenna set AT ₃ , and a fourth receiving antenna set AT ₄ are provided at each of the corners A, B, C, and D. These receiving antenna sets are configured as a set of a first receiving antenna and a second receiving antenna that are spaced apart from each other by 5 cm in a direction perpendicular to the side surface of the vehicle 300.

  The transmission antenna group 13 includes four transmission antennas 131, 132, 133, and 134 provided at the respective corners A, B, C, and D, respectively. All transmit antennas are excited by the same oscillator 10. The transmission antenna group 13 is only required to form an electromagnetic field by electromagnetic waves in the monitoring area, and the number and the installation position thereof are arbitrary.

  FIG. 4 is a diagram showing the configuration of the phase difference detector 2 for one receiving antenna set. The phase difference detector 2 detects a phase difference between the first reception signal S1 received by the first reception antenna 201A of the first reception antenna set 201 and the second reception signal S2 received by the second reception antenna 201B. Circuit. The first and second receiving antennas 201A and 201B are connected to input sides of multipliers (mixers) 23A and B via bandpass filters 21A and 21B and amplifiers 22A and 22B, respectively. The band-pass filters 21A and B transmit only the oscillation frequency band of the transmitter 10, and the amplifiers 22A and B amplify electric signals from the band-pass filters 21A and B, respectively.

A PLL (Phase-locked loop) circuit 24 is commonly connected to the other input side of the multipliers 23A and 23B. The PLL circuit 24 generates a signal whose frequency is close to the oscillation frequency of the oscillator 10. In the multipliers 23A and 23B, the first reception signal S1 output from the first reception antenna 201A and the second reception signal S2 output from the second reception antenna 201B are respectively multiplied by the signal from the PLL circuit 24. The first reception signal S1 and the second reception signal S2 are down-converted to an intermediate frequency electric signal that makes it easy to compare the phases. The output sides of the multipliers 23A and 23B are connected to two input sides of a multiplier (mixer) 28 via bandpass filters 25A and 25B, PLL circuits 26A and B, and amplifiers 27A and 27B, respectively. The band-pass filters 25A and 25B transmit only the signal in the intermediate frequency band, and the PLL circuits 26A and B are N times the frequency of the electric signal from the band-pass filters 25A and B (N is greater than 1). (Real number) and output. The amplifiers 27A and B amplify the electric signals from the PLL circuits 26A and B. The multiplier 28 multiplies the electric signals from the amplifiers 27A and 27B and outputs the result. The electrical signal output from the multiplier 28 is a low-frequency signal reflecting N times the phase difference between the first reception signal S1 and the second reception signal S2. The output side of the multiplier 28 is connected to a low pass filter 29. The output of the low-pass filter 29 is a phase difference signal α _n . The phase difference signal α _n is input to the audio signal generator 3 and the pseudo audio signal generator 4.

  When the interval between the first receiving antenna 201A and the second receiving antenna 201B is equal to or less than λ / 2 when the oscillation wavelength of the oscillator 10 is λ, the PLL circuits 26A and 26B have the first receiving signal S1 and the second receiving signal S2. Since the phase difference may become very small, it is provided to increase the phase difference and increase the S / N ratio.

FIG. 5 shows a configuration of an apparatus including the audio signal generator 3 and the pseudo audio signal generation apparatus 4. The audio signal generator 3 and the pseudo audio signal generation device 4 are common to the right ear system and the left ear system. The audio signal generator 3 includes a white noise source 30, a frequency band selector 31, and a variable gain amplifier 32. As will be described later, the frequency band selector 31 is a device that controls the signal band of the white noise source 30 based on the frequency of the phase difference signal α _n obtained from the n-th receiving antenna set AT _n . The faster the approaching speed of the monitoring object is, the higher the frequency band is, and the sound signal β _n whose amplitude increases as the monitoring object approaches the nth receiving antenna set AT _n is input to the convolution integrator 41. The convolution integrator 41 includes a right ear transversal filter in which a tap coefficient is set by a right ear head transfer function and a left ear transversal filter in which a tap coefficient is set by a left ear head transfer function.

Note that the apparatus shown in FIG. 5 is a digital processing circuit. The output of the white noise source 30 is a digital value obtained by sampling white noise. The digital value may be one that generates a random number by digital signal processing instead of sampling. The initial frequency band selection device 31, the variable gain amplifier 32, and the convolution integrator 41 are also devices that perform digital operations. The convolution integrator 41 is a device that performs convolution integration between the audio signal β _n corresponding to the _n- th receiving antenna set AT _n and the impulse response P _Rn of the right ear head transfer function Z _Rn . The signal output from the convolution integrator 41 is a pseudo audio signal A _Rn modulated by the phase difference signal α _n obtained from the n-th receiving antenna set AT _n . The pseudo audio signal A _Rn corresponding to the n-th receiving antenna set AT _n is synthesized by the synthesizer 42 to become a right ear pseudo audio signal R, which is converted into an analog signal by the D / A converter 43, It is output to the right receiver of the headphone 51. Similarly, in the left ear system, a convolution integrator 41 and a combiner 42 are configured. In the left ear system, the convolution integrator 41 is a device that performs convolution integration between the audio signal β _n corresponding to the nth receiving antenna set AT _n and the impulse response P _Ln of the left ear head transfer function Z _Ln . In the left ear system, the output of the convolution integrator 41 corresponding to the nth receiving antenna set AT _n becomes the pseudo audio signal A _Ln , and the pseudo audio signal A _Ln is synthesized by the synthesizer 42 to become the left ear pseudo audio signal L, It is converted into an analog signal and output to the left receiver of the headphone 51.

Next, the operation of the monitoring apparatus according to the first embodiment will be described.
First, an electrical signal is generated by the oscillator 10 of the exciter 1 and noise components and the like are removed by passing through the band-pass filter 11. Is formed.

  The electromagnetic waves in the monitoring range are received by the first and second receiving antennas 201A and 201B in each receiving antenna set. Since the first and second receiving antennas 201A and 201B are separated from each other, the first and second receiving antennas 201A and 201B are separated according to the relative distance between the transmitting antenna group 13 of the exciter 1 and the first and second receiving antennas 201A and 201B. The phases of the first reception signal S1 and the second reception signal S2 received by the second reception antennas 201A and 201B are different. Hereinafter, for simplification of description, the first reception signal S1 received by the first reception antenna 201A will be considered as cos (ωt + θA), and the second reception signal S2 received by the second reception antenna 201B will be considered as cos (ωt + θB). ω is 2πf, and f is the oscillation frequency of the oscillator 10.

  Only the frequency band of the oscillator 10 is transmitted through the band-pass filter 21A and cos (ωt + θA), which is the first reception signal S1, is amplified by the amplifier 22A. Further, cos (ωt + θB) that is the second received signal S2 is transmitted only through the frequency band of the oscillator 10 by the band-pass filter 21B, and the signal is amplified by the amplifier 22B.

The electric signals from the amplifiers 22A and 22B are multiplied by the electric signals from the PLL circuit 24 in the multipliers 23A and 23B, respectively. Assuming that the electrical signal from the PLL circuit 24 is sin (ω _LO t + θ _LO ), the output from the multiplier 23A is a component of sin (Δωt + θA−θ _LO ) and a component having a frequency of ω + ω _LO . Here, Δω = ω−ω _LO was set. A component having this frequency of ω + ω _LO is cut by the band pass filter 25A. Similarly, the output from the multiplier 23B is a component of sin (Δωt + θB−θ _LO ) and a component of frequency ω + ω _LO , and the component of frequency ω + ω _LO is cut by the band pass filter 25B.

The frequency and phase of the electrical signal from the band pass filter 25A are multiplied by N by the PLL circuit 26A, and an electrical signal sin (N × (Δωt + θA−θ _LO )) is output. Similarly, the frequency and phase of the electrical signal from the band pass filter 25B are multiplied by N by the PLL circuit 26B, and an electrical signal sin (N × (Δωt + θB−θ _LO )) is output.

The electric signals from the PLL circuits 26A and 26B are amplified by the amplifiers 27A and 27B, respectively, and then multiplied by the multiplier 28. The output from the multiplier 28 is a component of cos (Nψ) and a component having a frequency of 2NΔω. Here, ψ = θA−θB. ψ is the phase difference between the electrical signal S1 received by the antenna 20A and the electrical signal S2 received by the antenna 20B. Of these components, the component having a frequency of 2NΔω is cut by the low-pass filter 29, so that only the component of cos (Nψ) is sent to the audio signal generator 3 as the phase difference signal α _n .

The audio signal generator 3 calculates Nψ from cos (Nψ), and calculates a time change N * dψ / dt of Nψ, that is, a frequency. Then, the frequency is input to the frequency band selector 31, and the frequency band of white noise is selected. Further, the amplitude of cos (Nψ) changes the gain of the variable gain amplifier 32. Here, the time change of Nψ occurs in response to a change in the multipath environment formed between the exciter 1 and the n-th receiving antenna set AT _n . Changes in the multipath environment, the approach of monitoring the object in the region between the exciter 1 and the second n receive antenna pairs AT _n, caused by such withdrawal. Therefore, according to the monitoring apparatus of the first embodiment, it can be sensed by hearing the environmental change monitoring range between exciter 1 and the n receiving antenna pairs AT _n humans.

Next, the part which produces | generates audio | voice signal (beta) _n from the phase difference signal (alpha) _n in the audio | voice signal generator 3 is demonstrated. In FIG. 6, the phase difference signal α _n is input to the A / D converter 70, converted into a digital value, and input to the band pass filter 71. Only a meaningful signal band of the phase difference signal α _n is extracted by the band pass filter 71. From the output of the band pass filter 71, the frequency of the phase difference signal α _n is calculated. The output of the band pass filter 71 is input to the saturation amplifier 72, the output is input to the pulse edge detector 73, the output is input to the single pulse generator 74, and the output is input to the pulse flattener 75. That is, the phase difference signal α _n is amplified by the saturation amplifier 72 and shaped into a square wave having the same frequency as the frequency of the phase difference signal.

Next, the rising edge of the square wave is detected by the pulse edge detector 73. Next, in synchronization with the rising of the square wave, the single pulse generator 74 outputs a pulse signal having a constant pulse width. This pulse signal is a signal having the same frequency (cycle) as that of the phase difference signal α _{n and} a constant pulse width. Therefore, this pulse signal is a signal that is PDM modulated at the frequency of the phase difference signal α _n . The higher the pulse density of this pulse signal, the higher the frequency of the phase difference signal α _n . This pulse signal is input to the pulse flattener 75, and a DC value (frequency signal) proportional to the duty ratio is output. This frequency signal is input to the LCF adjustment unit 76 and the HCF adjustment unit 77. The LCF adjustment unit 76 determines a low-pass cutoff frequency of the pass band from the frequency signal, and the HCF adjustment unit 77 determines a high-pass cutoff frequency of the pass band. That is, when the frequency of the phase difference signal α _n is low, the low-frequency cut-off frequency and the high-frequency cut-off frequency are set low so that the low-frequency band signal passes through the frequency band selector 31 more. The When the frequency of the phase difference signal α _n is high, the low-frequency cutoff frequency and the high-frequency cutoff frequency are set high so that the high-frequency band signal passes through the frequency band selector 31 more. Thus, from the white noise source 30, audio signals beta _n pitch in proportion to the frequency of the phase difference signal alpha _n is obtained.

On the other hand, the output of the band pass filter 71 is input to the absolute value calculation unit 78, and the output thereof is input to the low pass filter 79. The absolute value calculator 78 detects the peak value of the phase difference signal α _n , and the low-pass filter 79 detects the envelope of the waveform formed by the peak value. That is, the low-pass filter 79 outputs an envelope signal of the phase difference signal α _n . This signal is input to the adjusting unit 80, and the adjusting unit 80 determines the gain of the variable gain amplifier 32. Therefore, the output signal of the variable gain amplifier 32 is a pitch corresponding to the frequency of the phase difference signal alpha _n, the audio signal beta _n of intensity according to the amplitude of the phase difference signal alpha _n.

  FIG. 7 shows the convolution integrator 41 and the combiner 42 in FIG. 5 so that the right ear system and the left ear system can be seen.

A right ear head transfer function that is a transfer function between the nth reception antenna set and the right ear is Z _Rn , and a left ear head transfer function that is a transfer function between the nth reception antenna set and the left ear is Z _Ln . As already defined, n-th reception antenna sets phase difference signal alpha _n obtained from the audio signal generated based on the phase difference signal alpha _n beta _n, HRTF Z _Rn to the audio signal beta _n, The pseudo audio signals obtained by _applying Z _Ln are A _Rn and A _Ln . The following equation holds.

ただし、Ｆ［ ］はフーリエ変換を表す。
また、疑似音声信号Ａ_Rnを、全位相差信号に対して合成して得られる右耳疑似音声信号Ｒ、疑似音声信号Ａ_Lnを、全位相差信号に対して合成して得られる左耳疑似音声信号Ｌは、次式で表現れる。

However, F [] represents a Fourier transform.
Also, the right ear pseudo audio signal R obtained by synthesizing the pseudo audio signal A _Rn with respect to the entire phase difference signal, and the left ear pseudo obtained by synthesizing the pseudo audio signal A _Ln with the total phase difference signal. The audio signal L is expressed by the following equation.

である。

It is.

ただし、∫（ ）dtは、畳み込み積分を意味する。

となる。 Further, when the impulse response of the right ear head transfer function Z _Rn is P _Rn and the impulse response of the left ear head transfer function Z _Ln is P _Ln , the following equation is established.

However, ∫ () dt means convolution integral.

It becomes.

In this way, the right ear pseudo audio signal R and the left ear pseudo audio signal L are obtained, and the audio based on these signals is output from the right and left receivers of the headphone 51 to the human right and left ears, respectively. In this way, humans feel as if a virtual sound source is present at the position where the monitored object is present in the auditory space. The phase difference signal α _n detected by the n-th receiving antenna set includes the position information of the monitored object observed from the position. Therefore, the audio signal β _n obtained by modulating the white noise with the phase difference signal α _n is converted into the right ear head transfer function between the installation position of the nth receiving antenna set and the right and left ears, the left ear head If a transfer function is transmitted and combined for all receiving antenna sets, a virtual sound source can be obtained at the position of the detected monitored object. The distance between the monitored object and the vehicle can be specified by the sound intensity, the approach speed by the pitch, and the direction by the direction in which the object can be heard. Thereby, the driver can recognize obstacles around the vehicle on the auditory space while driving.

  In addition, about the sound which a person feels, 20Hz-20kHz is an audible range. Further, the time resolution of sound is said to be 1 ms at the shortest, and it is necessary to use modulation of 1 kHz or less for sound discrimination. It is desirable to set the oscillation frequency of the oscillator 10 of the exciter 1 and the value of N of the PLL circuits 26A and B so that the frequency that changes with time of Nψ is in the range of 1 to 1000 Hz.

In the above embodiment, the convolution integration is used to obtain the pseudo audio signal. However, the audio signal may be transmitted to the head in the frequency space and the pseudo audio signal may be obtained by inverse Fourier change. That is, the audio signal β _n is Fourier-transformed to obtain F [β _n ]. Next, the product of the right ear head transfer function Z _Rn , the left ear head transfer function Z _Ln , and F [β _n ] is obtained from the equations (1) and (2). Next, the sum of the product Z _Rn F [β _n ] and the sum of the products Z _Ln F [β _n ] are obtained for all receiving antenna groups by the equations (3) and (4), and the inverse of each sum is obtained. The right ear pseudo audio signal R and the left ear pseudo audio signal L may be obtained by Fourier transform. This calculation may be executed in real time. Further, the section of the Fourier transform may be set by a window function having an appropriate time length.

In the present embodiment, a plurality of speakers are used instead of headphones. An example in which two speakers are used will be described.
The transfer matrix between each speaker and the human right and left ears is a 2 × 2 matrix. Each component of the transfer matrix is a transfer function between each speaker and the right and left ears. That is, the first row component of this transfer matrix is each first transfer function, and the second row component is each second transfer function. Let this transfer matrix be B. A pseudo audio signal to be input to two speakers is represented by a 2 × 1 column vector D. Speech input to the right and left ears is represented by a 2 × 1 column vector C. The following equation holds.

また、上記の第ｎ受信アンテナ組ＡＴ_n と右耳、左耳間の頭部伝達関数Ｚ_Rn、Ｚ_Lnを成分とする２×４の行列を伝達行列Ｚとする。音声信号β_n を成分とする４×１の列ベクトルをβとする。ただし、受信アンテナ組の数を４としている。すなわち、ｎ＝１，２，３，４である。
疑似音声信号（Ｒ，Ｌ）は、次式で表される。

この式が、（９）のＦ［Ｃ］に等しくなるように、各スピーカに入力される疑似音声信号Ｄを生成すれば良い。
すなわち、次式が成立する。

よって、

すなわち、頭部伝達行列Ｚと、各スピーカと右耳、左耳間の伝達行列Ｂとを用いて、各受信アンテナ組と各スピーカ間の伝達行列Ｂ^-1Ｚを得ることができる。２×４の伝達行列Ｂ^-1Ｚの各成分が各受信アンテナ組と各スピーカ間の伝達関数であり、第３伝達関数である。Ｂ^-1Ｚのインパルス応答Ｆ^-1［Ｂ^-1Ｚ］と、音声信号βとの畳み込み積分をすれば、各スピーカに入力すべき疑似音声信号Ｄを得ることができる。この疑似音声信号Ｄにより音を各スピーカから出力すれば、人間は、実施例１と同様に仮想音源を監視物体の位置に認識することができる。

In addition, a 2 × 4 matrix having the above-mentioned head-related transfer functions Z _Rn and Z _Ln between the _n- th receiving antenna set AT _n and the right and left ears as a component is a transfer matrix Z. A 4 × 1 column vector whose component is the audio signal β _n is β. However, the number of reception antenna groups is four. That is, n = 1, 2, 3, 4.
The pseudo audio signal (R, L) is expressed by the following equation.

What is necessary is just to produce | generate the pseudo audio | voice signal D input into each speaker so that this formula may become equal to F [C] of (9).
That is, the following equation is established.

Therefore,

That is, using the head-related transfer matrix Z and the transfer matrix B between each speaker and the right and left ears, the transfer matrix B ⁻¹ Z between each receiving antenna set and each speaker can be obtained. Each component of the 2 × 4 transfer matrix B ⁻¹ Z is a transfer function between each receiving antenna set and each speaker, and is a third transfer function. B and ^-1 Z of the impulse response F ^-1 [B ^-1 Z], if the convolution of an audio signal beta, it is possible to obtain a pseudo audio signal D to be inputted to the speaker. If sound is output from each speaker by the pseudo audio signal D, a human can recognize the virtual sound source at the position of the monitored object as in the first embodiment.

When four speakers are used, the transmission matrix B between the speaker, the right ear, and the left ear is a 2 × 4 matrix, and B ⁻¹ is not defined, but two 2 × 2 small matrices are paired. B ⁻¹ can be obtained by defining the matrix B with an expanded 4 × 4 matrix in which the other components are set to 0 at the corners.
FIG. 8 shows an example in which four speakers 52 are used. The convolution integrator 46 is an integrator for obtaining a matrix of convolution integral with (β _1, β _2, β _3, β ₄ ) and the impulse response F ⁻¹ [B ⁻¹ Z]. The D / A converter 43 converts the pseudo audio signal D (four components) from a digital value to an analog value and outputs the analog value to each speaker 52.

In the third embodiment, convolution integration is used to obtain the pseudo audio signal. However, even if the audio signal is transmitted to the speaker in the frequency space and the pseudo audio signal input to each speaker is obtained by inverse Fourier change. good. That is, the audio signal β is Fourier-transformed to obtain F [β]. Next, the matrix F [D] of the Fourier transform of the pseudo audio signal input to the speaker is obtained by the product of the transfer matrix B ⁻¹ Z and F [β] by the equation (12). A matrix D of pseudo sound signals to be input to each speaker can be obtained by inverse Fourier transform of F [D].

[Experimental example]
FIG. 9 shows the waveform of the phase difference signal α _n detected by each receiving antenna set when a person walks around the vehicle in the apparatus of the first embodiment. It can be seen that the amplitude of the phase difference signal α _n gradually increases as it approaches each receiving antenna set.
FIG. 10 shows an enlarged waveform of one phase difference signal α _n . The frequency was about 7 Hz. Further, FIG. 11 shows an enlarged waveform of one phase difference signal α _n when a person walks around the vehicle in a small running area. The frequency was approximately 17-20 Hz. It is understood that the frequency of the phase difference signal α _n increases as the moving speed of the monitored object increases.

An example of use of the present apparatus in a device other than a vehicle is shown below.
[Usage example 1]
The exciter 1 and the receiving antenna set are attached to the human body. For example, attach to fingers, hands, arms, legs, etc. If it does in this way, the approach direction and approach situation of a monitoring object to a human body can be detected by hearing.

[Usage example 2]
The exciter 1 is attached to the first human body, and the device below the receiving antenna set is attached to the second human body that is a third person. In this way, the second human body can sense by hearing which part of the first human body has moved.

[Usage example 3]
The exciter 1 is attached to a moving body. A device below the receiving antenna set is attached to a person. In this way, the person can sense the situation where the moving body approaches by hearing.

  The present invention can be applied, for example, to an apparatus that monitors an obstacle around a vehicle by hearing.

1: Exciter 2: Phase difference detector 20: Reception antenna set 3: Audio signal generator 4: Pseudo signal generator 5: Audio output device 10: Oscillator

Claims (6)

In a monitoring device that informs humans of the approach of objects in the monitoring range around humans with sound,
An exciter that outputs electromagnetic waves to the monitoring range;
The first receiving antenna and the second receiving antenna in which the electromagnetic waves output from the exciter are arranged at predetermined intervals are set as a set, and each set of antennas is disposed at a plurality of positions in the monitoring range. Multiple sets of receive antennas;
A phase difference signal detector that is provided for each of the reception antennas of each set and detects a phase difference signal between a first reception signal received by the first reception antenna and a second reception signal received by the second antenna When,
An audio signal generator that generates an audio signal having an intensity corresponding to the amplitude of each phase difference signal detected by the phase difference signal detector;
Each installation position for each receiving antenna of each set and each right ear head transfer function and each left ear head transfer function which are respective transfer functions between the right and left ears of the human, and the audio signal generator Based on the sound signals output from the sound antenna, the sound signals to be detected by the human right and left ears so that the sound sources of the sound signals exist at the installation positions of the receiving antenna. A pseudo audio signal generating device for generating a pseudo audio signal;
An audio output device that outputs a signal output from the pseudo audio signal generation device as sound to the right and left ears of the human;
The monitoring apparatus characterized by having.   The monitoring apparatus according to claim 1, wherein the audio signal generator generates the audio signal having a frequency corresponding to a frequency of each phase difference signal and an intensity corresponding to an amplitude of each phase difference signal. The pseudo audio signal generation device generates a right ear pseudo audio signal for the right ear by combining each signal obtained based on each audio signal and each right ear head transfer function, and each audio signal and the A device for generating a left-ear pseudo-voice signal for the left ear by synthesizing each signal obtained based on each left-ear head transfer function,
The audio output unit inputs the right ear pseudo audio signal, outputs audio to the human right ear, inputs the left ear pseudo audio signal, and outputs audio to the human left ear, respectively. The monitoring device according to claim 1, wherein the monitoring device is a device that performs monitoring. The audio output device is a speaker arranged at each of a plurality of locations around the human,
The pseudo audio signal generation device includes: a first transfer function between each speaker and a right ear; a second transfer function between each speaker and a left ear; the right ear head transfer function; By combining each signal obtained based on each installation position obtained for each receiving antenna based on the left ear head transfer function, each third transfer function between each speaker, and each audio signal The monitoring device according to claim 1, wherein the monitoring device is a device that generates a pseudo audio signal to be output to each speaker. The pseudo audio signal generation device generates a right ear pseudo audio signal for the right ear by combining each signal obtained by convolution integration of each audio signal and each impulse response of each right ear head transfer function, The apparatus for generating a left-ear pseudo-voice signal for the left ear by combining each signal obtained based on each voice signal and each impulse response of each left-ear head-related transfer function. The monitoring device described in 1. The pseudo audio signal generation device is a device that generates a pseudo audio signal to be output to each speaker by combining each signal obtained by convolution integration of each audio signal and each impulse response of each third transfer function. The monitoring apparatus according to claim 4, wherein the monitoring apparatus is provided.

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