JP2010076715A - Noise reduction device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device attaining an effective reduction of noise by small power-consumption according to variation in installation environment in a noise reduction device mounted on an aircraft or the like. <P>SOLUTION: The noise reduction device includes: a noise detection means 10 for detecting the noise; a noise control means 11 for generating a control sound signal for cancelling the noise detected with the noise detection means 10 based on information from the noise detection means 10; and a control sound output means 12 for outputting the control sound based on the control sound signal from the noise control means 11. The control characteristic of the noise control means 11 is changed to an optimum characteristic based on the environment characteristic from an environment characteristic input means 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a noise reduction device and a noise reduction system, and more particularly to a noise reduction device used in a sealed structure such as an aircraft or a railway vehicle.

  When providing information such as voice service to a user seated in a seat in an aircraft or vehicle having a high noise level, noise in the seat becomes a problem.

  When using an internal space that is bounded by continuous walls, such as an aircraft or a vehicle, the use location is a kind of sealed structure, and if there are noise sources inside and outside the use location, it will be difficult for the user. The noise environment will be fixed. For this reason, depending on the level of noise, noise becomes a physical and mental pressure factor on the user, and the comfort of the place of use decreases. In particular, when a service is provided to a user as a cabin such as an aircraft, the quality of service work is seriously hindered, such as preventing a good sleep and making conversation difficult.

  In particular, in the case of aircraft, it is generated as the aircraft moves through the air layer, such as the noise of equipment that generates thrust of the aircraft centered on propellers and engines, and wind noise generated by the tip of the aircraft and both wings during flight. Since the sound related to the air flow is a major noise source, the in-flight noise causes discomfort to passengers and hinders voice services and the like.

  On the other hand, as a countermeasure for reducing noise in the sealed room, conventionally, a method using a passive damping means has been generally used, and a sound insulating material having acoustic absorptivity such as a barrier material or an absorbing material is used as the sealed structure. Noise can be reduced by disposing it between the generation source. As the barrier material, for example, a high-density barrier material is used, and as the absorbing material, for example, a sound absorbing sheet is used. However, materials having acoustic absorption generally have a high density, and high density materials are associated with increased weight. As the weight increases, the flight fuel increases and the cruising range decreases. Therefore, the economical efficiency and function as an aircraft are reduced. In addition, as a structural material, deterioration in function in terms of strength such as being easily damaged and design in terms of texture cannot be ignored.

  As a method of reducing noise by the active attenuation means, a method of generating a sound wave having a phase opposite to that of the noise has been generally practiced. Yes. By this method, the noise level can be reduced at or near the generation source, and the noise can be prevented from propagating to the area where the noise needs to be reduced. Examples of specific applications include a microphone that detects sound generated from a noise source, a controller that amplifies the electrical signal input from the microphone and inverts the phase, and converts the electrical signal input from the controller into sound. An audio erasing device including an oscillating speaker has been proposed (see, for example, Patent Document 1).

  In recent years, methods for taking noise countermeasures from the viewpoint of improving convenience in passenger seats have been studied based on the above-described method of reducing noise by active damping means in a moving body such as an aircraft. For example, a user can install a sound reduction device for each seat and install a speaker, microphone, and controller near the seat, or a plurality of speakers and microphones placed near the user seated in the seat. There has been proposed a method (for example, refer to Patent Documents 2 to 3) for improving the noise reduction effect on the noise.

In addition, as a method to effectively mute following the environmental change of the moving body, the temperature of the moving body is monitored and the propagation characteristics between the speaker and the microphone are changed following the temperature change to improve the noise reduction effect. Proposed (see Patent Document 4) and a method (see Patent Document 5) for enhancing the silencing effect by detecting sound depending on the traveling speed with a microphone and performing adaptive processing.
Japanese Patent Laid-Open No. 1-270489 JP-A-5-289676 Japanese Patent Laid-Open No. 5-281980 Japanese Patent Laid-Open No. 10-49175 JP 7-319480 A

  However, the above method has a problem that the calculation load and power consumption for noise reduction are always large, and even when the environment changes and the calculation load and power consumption can be reduced, these are not changed. SUMMARY OF THE INVENTION The present invention solves the above problems, and an object of the present invention is to provide an effective noise reduction device for a user with low power consumption by reducing the calculation load in accordance with a change in the environment of a moving body. In addition, when reducing the computational load by reducing the number of microphones used, it is possible to reduce the frequency of use of the microphones by selecting the microphones to be used in order, reducing the deterioration of the microphones and extending the life of the device. Can be extended. Furthermore, it is possible to reduce the probability that abnormal sound is generated due to the liquid being applied to the operating microphone, the touching of the operating microphone, etc., and highly reliable control is possible.

  In order to achieve the above-described object, a noise reduction device according to claim 1 of the present invention is a device installed on a moving body, and a noise detection means for detecting noise emitted from a noise source, A noise control means for generating a control sound for reducing the noise detected by the noise detection means, a control sound output means for outputting the control sound, and an environmental characteristic input means for inputting the environmental characteristics of the moving body, The control sound is optimized based on environmental characteristics. With such a configuration, it is possible to optimize the control sound based on the environmental characteristics of the mobile body, reduce the calculation load according to the environmental change of the mobile body, and reduce noise effectively for the user with low power consumption An apparatus can be provided.

  According to a second aspect of the present invention, there is provided a noise reduction apparatus comprising residual sound detection means for detecting a residual sound obtained by reducing noise with a control sound, and optimizing the control sound based on environmental characteristics and the residual sound. It is characterized by. With such a configuration, it is possible to optimize the control sound based on the environmental characteristics of the mobile body, reduce the calculation load according to the environmental change of the mobile body, and reduce noise effectively for the user with low power consumption An apparatus can be provided.

  The noise reduction device according to claim 3 of the present invention is characterized in that the environmental characteristic is altitude information of the moving body. With such a configuration, it is possible to optimize the control sound based on the altitude information of the moving body, reduce the calculation load according to the environmental change of the moving body, and reduce the noise effectively for the user with low power consumption An apparatus can be provided.

  The noise reduction apparatus according to claim 4 of the present invention is characterized in that the environmental characteristic is speed information of the moving body. With such a configuration, it is possible to optimize the control sound based on the speed information of the moving body, reduce the calculation load according to the environmental change of the moving body, and reduce the noise effectively for the user with low power consumption An apparatus can be provided.

  The noise reduction device according to claim 5 of the present invention is characterized in that the environmental characteristic is route information of the moving body. With this configuration, it is possible to optimize the control sound based on the route information of the moving body, reduce the calculation load according to the environmental change of the moving body, and reduce noise effectively for the user with low power consumption. An apparatus can be provided.

  Further, in the noise reduction device according to claim 6 of the present invention, the number of used noise detection means when the altitude information is low altitude is n, and the number of noise detection means used when the altitude information is high is m. It is characterized by optimizing so that the number of noise detection means used at a low altitude is smaller than the number of noise detection means used at a high altitude (n <m). With such a configuration, it is possible to optimize the number of noise detection means used based on the altitude information of the moving body, reduce the calculation load according to changes in the environment of the moving body, and reduce power consumption to the user. It is possible to provide an effective noise reduction device.

  In the noise reduction device according to claim 7 of the present invention, the noise control means is constituted by a digital filter, the number of taps of the digital filter when the altitude information is low altitude is p, and the digital filter is high when the altitude information is high. The number of taps is q, and optimization is performed so that the number of taps of the digital filter at a low altitude is smaller than the number of taps of the digital filter at a high altitude (p <q). With such a configuration, it is possible to optimize the number of taps of the digital filter based on the altitude information of the moving body, reducing the calculation load according to the environmental change of the moving body, and effective for the user with low power consumption. It is possible to provide a simple noise reduction device.

  In the noise reduction device according to claim 8 of the present invention, the number of used noise detecting means when the speed information is high is a, the number of noise detecting means used when the speed information is low, and b. The number of noise detection means used at the time is optimized to be less than the number of noise detection means used at a low speed (a <b). With such a configuration, it is possible to optimize the number of noise detection means used based on the speed information of the moving body, reducing the calculation load according to changes in the environment of the moving body, and reducing the power consumption. It is possible to provide a typical noise reduction device.

  In the noise reduction apparatus according to claim 9 of the present invention, the noise control means is constituted by a digital filter, the number of taps of the digital filter when the speed information is high is s, and the number of taps of the digital filter is low. It is characterized in that the number is t and the number of taps of the digital filter at high speed is less than the number of taps of the digital filter at low speed (s <t). With such a configuration, it is possible to optimize the number of taps of the digital filter based on the speed information of the moving body, reducing the calculation load in accordance with the environment change of the moving body, and effective for the user with low power consumption. It is possible to provide a simple noise reduction device.

  According to the noise reduction device and the noise reduction system of the present invention, it is an object to provide a noise reduction device that is effective for a user with low power consumption by reducing a calculation load in accordance with an environmental change of a moving body. In addition, when reducing the computational load by reducing the number of microphones used, it is possible to reduce the frequency of use of the microphones by selecting the microphones to be used in order, reducing the deterioration of the microphones and extending the life of the device. Can be extended. Furthermore, it is possible to reduce the probability that abnormal sound is generated due to the liquid being applied to the operating microphone, the touching of the operating microphone, etc., and highly reliable control is possible.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

(Embodiment)
The noise reduction device according to the embodiment of the present invention will be described below with reference to a case where it is mounted on an aircraft.

  First, the basic configuration of the noise reduction device of the present invention will be described with reference to FIG. In FIG. 1, 10 is a noise detection means, 11 is a noise control means, 12 is a control sound output means, 13 is an environmental characteristic input means, and 14 is a residual sound detection means.

  In the noise reduction device of the present invention, noise is detected by the noise detection means 10, converted into a noise signal, and output to the noise control means 11. Based on the input noise signal, the noise control unit 11 generates a sound wave having an opposite phase capable of reducing noise as a control sound signal and outputs the control sound signal to the control sound output unit 12. The control sound output means 12 oscillates, as a control sound, a sound wave having an opposite phase that can reduce noise based on the input control sound signal, and reduces noise. At this time, the control characteristic of the noise control unit 11 can be changed to an optimum characteristic by the environmental characteristic from the environmental characteristic input unit 13. Further, the residual sound after this control is detected by the residual sound detection means 14 and is fed back to the noise control means 11 as a residual sound signal, so that it is possible to obtain optimum control characteristics, and it can be installed as necessary. Use properly or not.

  In the present embodiment, as an example, the noise detection unit 10 will be described as a noise microphone, the control sound output unit 12 as a speaker, and the residual sound detection unit 14 as a residual sound microphone.

  Next, a noise environment in an aircraft that requires installation of a noise reduction device will be described with reference to FIGS.

  First, the noise environment of the entire aircraft according to the embodiment of the present invention will be described with reference to FIG. In FIG. 2, 100 is an aircraft, 101a and 101b are left and right wings, and 102a and 102b are left and right engines. A, B, and C respectively indicate cabins in the cabin and are provided with seat rows such as 103a, 103b, and 103c. NS1a, NS1b, and NS1c are main noise sources. Further, D is a space combining the guest room A and the guest room B, and will be described later with reference to FIG.

  From the viewpoint of the noise environment of an aircraft, the engine is an important noise source because it involves not only the rotational noise but also the reverberation of the air flow. From the passenger service standpoint, the engines 102a, 102b are seat rows 103a, 103b installed in the cabin A (eg, first class), cabin B (eg, business class) and cabin C (eg, economy class), for example. , 103c acts as external noise sources NS1a and NS1b on each part of the fuselage, and collision noise (wind noise) with the airflow at the tip of the fuselage and both wings as the fuselage moves through the air layer at high speed However, the noise source NS1c adversely affects the in-flight information providing service and the conversation between passengers and passengers.

  Next, the noise environment in the aircraft according to the embodiment of the present invention will be described with reference to FIG. In FIG. 3, the space D in FIG. 2 is shown enlarged. 3, 105 denotes a seat, NS2a, NS2b, NS2c, NS2d, and NS2e denote noise sources, and NS1a, NS1b, and NS1c denote the same noise sources as in FIG.

  The space D is divided into a guest room A and a guest room B by walls. As the sound environment of the space D, noise sources NS1a and NS1b generated from the engines 102a and 102b and wind noise NS1c at the front end of the fuselage exist as external noise sources as shown in FIG. NS2a to NS2e exist as internal noise sources. Considering this as noise in one seat 105 arranged in the cabin A, the seat 105 has an engine 102a (FIG. 2) attached to the wings outside the window and noise sources NS1a to NS1c caused by airflow noise and The noise sources NS2a to NS2e caused by the air conditioner are affected by noise.

  In particular, in the first class shown in FIG. 2 and FIG. 3 in the guest room A, the seat has a shell structure, and inside the shell is a viewing device such as a television or radio for enjoying movies and music, a business There are desks for PCs, PC connection power supplies, etc., and there is a strong demand to provide passengers with an environment where they can relax and concentrate on business. For this reason, there is a particularly great demand for noise reduction inside the shell, and although the shell itself uses a material having a soundproofing effect, it is possible to efficiently reduce the noise around the shell and through the shell. It becomes important. However, it is necessary to increase the thickness and weight of the shell in order to enhance the soundproofing effect with the conventional technology, and it is difficult to realize the installation on an aircraft for reasons such as installation space and weight. On the other hand, in the muffler system using the present invention, noise reduction can be realized without taking up installation space and weight, and a comfortable environment can be provided to passengers.

  Next, a block diagram of the noise reduction apparatus according to the embodiment of the present invention will be described with reference to FIG.

  In FIG. 4, 300 is a noise reduction device, 331 and 335 are A / D converters, and 334 is a D / A converter. Reference numeral 332 denotes a digital filter, and reference numeral 333 denotes a control unit. Reference numeral 301 denotes a user, and 302 denotes a user's ear. 1, 10 is a noise microphone, 11 is a noise control means, 12 is a speaker, 13 is an environmental characteristic input means, and 14 is a residual sound microphone.

  The noise reduction apparatus 300 includes a noise microphone 10, a noise control unit 11, a speaker 12, an environmental characteristic input unit 13, and a residual sound microphone 14. Hereinafter, each structure and function are demonstrated.

  The noise microphone 10 is provided as noise detection means for detecting noise emitted from some noise source 310, and has a function of detecting noise information, converting it into a noise signal, and outputting it.

  The noise control means 11 includes A / D converters 331 and 335, a digital filter 332, a control unit 333, and a D / A converter 334, noise information from the noise microphone 10 and residual sound of the residual sound microphone 14. Based on the signal, a control sound signal having a phase opposite to that of the noise is generated so that the residual sound is minimized, and the speaker 12 is controlled.

  The A / D converter 331 A / D converts the noise signal from the noise microphone 10 and outputs the converted signal to the digital filter 332 and the control unit 333. The digital filter 332 is composed of multi-stage taps, and is an FIR filter that can freely set the filter coefficient of each tap. In addition to the information from the noise microphone 10, residual sound information from the residual sound microphone 14 is input to the control unit 333 via the A / D converter 335, so that the residual sound is minimized. Each filter coefficient of the digital filter 333 is adjusted. That is, a control sound signal that reduces noise from the noise source 310 at the installation position of the residual sound microphone 350 is generated and output to the speaker 12 via the D / A converter 334. The speaker 12 has a function of converting a control sound signal received from the D / A converter 334 into a sound wave and generating a control sound for reducing noise in the vicinity of the ear 302 of the user 301.

  The environmental characteristic input means 13 inputs the environmental characteristics of the moving body to the noise control means 11, and the noise control means 330 changes the control characteristics to the optimum one based on the environmental characteristics.

  It should be noted that the environmental characteristic detection means that gives environmental characteristics to the environmental characteristic input means 13, for example, an altimeter or a speedometer, does not need to be close to the environmental characteristic input means 13, as long as the environmental characteristics can be input to the environmental input means. It can be installed anywhere.

  As shown in FIG. 4A, in the noise reduction apparatus 300 according to the embodiment of the present invention, the noise emitted from the noise source 310 is detected by the noise microphone 10, and the signal is processed by the noise controller 11 and the speaker. The control sound is output from No. 12, and the noise emitted from the noise source 310 by the user 302's ear 302 is superimposed on the sound having the inverted phase to reduce the noise.

  FIG. 4B shows a method for superimposing the control sound output from the speaker 12 and the noise emitted from the noise source 310.

  When the noise spread angle is 310α with respect to the main arrival path 310N of the noise connecting the noise source 310 and the ear 302 of the user 301, the speaker 12 is arranged inside the spread angle 310α. Thereby, the control sound emitted from the speaker 12 with the phase reversed is superimposed on the noise and reaches the ear 302 of the user 301. Further, by arranging the residual sound microphone 14 in the overlapping region, it is possible to detect the residual sound after the noise reduction and to feed back the operation result of the noise reduction device 300, thereby enhancing the noise reduction effect. .

  Next, an installation example of the noise reduction device of the present invention on a seat in an aircraft will be described with reference to FIG. In FIG. 5, 630 is a seat and 650 is a shell surrounding the seat. Further, 10a to 10m are noise microphones as with 10 in FIG. 1 and are distinguished by subscripts because there are a plurality of them. Reference numerals 12a and 12b are speakers as in the case of 12 in FIG. As in FIG. 3, reference numeral 300 denotes a noise reduction device, and 301 denotes a user.

  Noise is detected by the noise microphones 10 a to 10 l attached to the shell 650 that surrounds the seat 630, and the detected noise signal is output to the noise reduction device 300 installed in the shell 300. The noise reduction apparatus 300 generates a control sound signal having an opposite phase based on the noise signal and outputs it to the speakers 12a and 12b. The speakers 12 a and 12 b oscillate a control sound based on the control sound signal, and can reduce the noise at the ear of the user 301 sitting on the seat 630.

  In addition, although the case where the number of noise microphones was 10 was demonstrated as an example here, the number of noise microphones is not restricted to this. Any number of microphones may be installed as long as the number of noise microphones is one or more. Further, although the case where the number of speakers is two has been described, the number of speakers is not limited to this, and any number of speakers may be arranged as long as the number is one or more.

  Although the case where the noise microphone 10 and the speakers 12a and 12b are installed in the shell 650 has been described here, the installation location is not limited to the shell 650. For example, it may be installed on the seat 630, may be installed on the floor, or installed anywhere where a similar effect can be expected.

  Although the case where the noise reduction device 300 is installed inside the shell 650 has been described here, it may be arranged inside the seat 630 or may be installed close to the seat 630 or the shell 650. . In addition, it is obvious that it may be installed anywhere as long as it can receive the noise signal from the noise microphone 10 as an input and output the control sound signal to the speaker 12.

  Next, the characteristics of aircraft noise and the operating principle of the present invention will be described with reference to FIG. FIG. 6 shows the frequency characteristics of aircraft noise during flight. The solid line shows the characteristics at low altitude flight, and the dotted line shows the characteristics at high altitude flight. The vertical axis represents the sound pressure level and the horizontal axis represents the frequency. When the altitude is high, it can be seen that the sound pressure level is low in the low frequency band. This is mainly because the engine output can be suppressed because the air density is low at high altitudes and the aircraft can fly with a small air resistance. Conversely, at low altitudes, the engine output increases and the low frequency band derived from the engine becomes dominant. Here, noise that is dominant in the low range can be effectively silenced even if the number of noise microphones is reduced, so it can be calculated with sufficient noise reduction effect by reducing the number of noise microphones at low altitudes. The amount and power consumption can be reduced.

  Next, a specific operation of the present invention will be described with reference to FIG. FIG. 7A shows a high altitude flight, and FIGS. 7B1 and 7B2 show a low altitude flight, respectively. 7 (a1), 7 (b1), and 7 (b2) are the same as those in FIG. 5, 10a to 10m are noise microphones, 12a and 12b are speakers, and 300 is a noise reduction device. , 301 indicates a user.

  At the time of high altitude flight, the noise reduction effect is obtained by using the noise microphones 10a to 10m installed as shown in FIG. When flying at a high altitude, as shown in FIGS. 7 (b1) and 7 (b2), the amount of calculation can be reduced by reducing the number of noise microphones 10 used when the altitude is low. And power consumption can be reduced. Here, FIG. 7 shows a case where the number of noise microphones to be used is halved, but any number of noise microphones may be used as long as the desired effect of the user can be obtained.

  Here, the description is divided into two stages of high altitude flight and low altitude flight, but the number of noise microphones to be used may be set in more stages for each altitude. For example, it is divided into four levels, altitude a, altitude b, altitude c, altitude d, in descending order of altitude, and by setting the noise microphone 10 to be used corresponding to these, the microphone used corresponding to the four levels of height The number can be changed. Of course, this step may be three steps, and it is obvious that the same effect can be obtained even when there are more than five steps.

  In FIGS. 6B1 and 6B2, the noise microphones to be used and the noise microphones not to be used are set to be reversed. By alternating between the two at high altitudes, the operating time of the noise microphone can be halved, deterioration due to the use of the noise microphone can be reduced, and the life of the apparatus is extended. This is also possible by setting the number of noise microphones to be used in more stages for each altitude and selecting the noise microphones 10 to be used in order, thereby suppressing deterioration due to the use of the noise microphones 10 and extending the life of the device. It becomes possible.

  Further, it is not always necessary to use all installed noise microphones 10 at the time of high altitude flight, and noise microphones 10 that are not used may be provided as spares. In this case, by changing the noise microphone 10 to be used as necessary, deterioration due to use of the noise microphone 10 can be suppressed and the life of the apparatus can be extended.

  In addition, depending on the installation state of the noise microphone 10, there is a possibility that a passenger spills a drink and liquid is applied to the noise microphone 10, or a user hits the noise microphone 10 to generate an abnormal sound. Even in such a case, by reducing the number of noise microphones 10 to be used, it is possible to reduce the probability of occurrence of abnormal sounds.

  In addition, when a noise source that emits particularly loud noise such as an engine can be identified, the noise microphones 10 arranged in the direction of the noise source are preferentially used, so that more noise microphones 10 can be used. Can be effectively reduced.

  Next, a case where power consumption is reduced by reducing the number of taps will be described. High-frequency noise such as wind noise and air conditioning increases the influence of reflection and diffraction. (Sampling period) x (number of taps) is the response length of the filter, and in order to express the influence of reflection and diffraction with the filter, it is necessary to lengthen the response length. For this purpose, it is necessary to increase the number of taps of the filter. Conversely, such a problem does not occur with low-frequency noise, so that the silencing effect can be maintained even if the number of filter taps is reduced. In this way, noise that is dominant in the low range can be effectively silenced even if the number of taps of the filter is reduced. Therefore, by reducing the number of 8 taps of the filter at low altitudes, a sufficient silencing effect can be achieved. The amount of calculation and power consumption can be reduced while maintaining the above.

  Next, a method for selecting an appropriate number of noise microphones and filter coefficients will be described with reference to FIG. This noise reduction apparatus operates based on the flowchart shown in FIG. State s810 is an environment characteristic reading state, s820 is an altitude change determination state, and s830 is a state in which the number of noise microphones and filter coefficients are read. After reading the altitude information of the aircraft in the state s810, the noise control means 11 determines whether there is a change in the altitude information in the state s820. If there is a change, the process moves to state s830, where the number of noise microphones and the filter coefficient are changed to the optimum state obtained in advance, and after a predetermined time, returns to state s810. When there is no high change in the state s820, the process returns to the state s810 after a certain time. By repeating this processing, it is possible to select an appropriate number of noise microphones based on altitude information.

  Next, a method for selecting an appropriate number of taps and filter coefficients will be described with reference to FIG. The noise reduction apparatus operates based on the flowchart shown in FIG. 9, and optimizes the number of filter taps and filter coefficients. The noise control unit 11 reads the altitude information of the aircraft in the state s910, and then determines whether there is a change in the altitude information in the state s920. When there is a change, the process moves to state s930, the number of taps and the filter coefficient are changed to the optimum state obtained in advance, and the process returns to state s910 after a predetermined time. When there is no change in the altitude in the state 920, the process returns to the state s910 as it is after a predetermined time. By repeating this processing, it is possible to select an appropriate number of taps based on altitude information.

  As described above, according to the present embodiment, it is possible to optimize the number of noise microphones and the number of filter taps by using the altitude information of the airplane as the environmental characteristics, which is optimal according to the environment. The effect can be provided with low power consumption.

  Next, the case of using airplane speed information as environmental characteristics will be described. When an airplane flies at a high speed, it is necessary to increase the engine output as compared with a case where the airplane flies at a low speed, and noise in a low frequency region caused by the engine increases. Therefore, when flying at high speed, it is possible to effectively mute the sound while reducing the amount of calculation and power consumption by reducing the number of noise microphones and the number of taps as in the case of low altitude. In addition, all other effects can be obtained when the altitude information is used as the environmental characteristics, such as extending the product life and preventing the occurrence of abnormal noise.

  Next, the case where route information is used as environmental characteristics will be described. In general, the route of an airplane is determined by departure point information, destination information, climatic conditions, cruising status of other airplanes, and the like. Of these, focusing on climatic conditions, for example, it can be seen that the vibrations and stagnation of the fuselage increase and the low-frequency noise increases when the atmosphere is unstable. For this reason, the number of noise microphones and the number of taps can be reduced based on this climatic condition, and the amount of calculation and power consumption can be reduced. In addition, all other effects can be obtained when the altitude information is used as the environmental characteristics, such as extending the product life and preventing the occurrence of abnormal noise.

  In addition, regarding altitude information and speed information, by using altitude information and speed information that has been previously obtained as route information at the stage of route design before takeoff, the number of noise microphones and taps can be determined without using real-time measurement values. Reductions are also possible.

  In the present embodiment, the digital filter using the FIR filter has been described as a method for realizing the noise control means. However, this may be an analog filter. In this case, analog filter characteristics may be selected by enabling selection of multiple elements as operations corresponding to reading coefficients with digital filter coefficients, or multiple analog filters having different characteristics may be prepared and selected. May be. Any other configuration that can select desired characteristics may be realized.

  Further, in the embodiment of the present invention, in addition to the noise microphone 320 as sound detection means for detecting noise emitted from the noise source 310, a residual sound microphone 350 for detecting control sound output from the speaker 340 is provided. The residual sound microphone 350 can detect and correct the synthesized sound of the noise and the control sound as the residual sound. However, the residual sound microphone 350 is an essential component for the noise reduction device according to the embodiment of the present invention. is not. Since the residual sound microphone 350 is usually disposed in the vicinity of the user's head, the configuration of the seat in the vicinity of the user's head can be simplified by omitting the residual sound microphone 350. Therefore, it is possible to realize a low-cost noise reduction device that is free from psychological pressure and is convenient for the user.

  In the present embodiment, the case where the present noise reduction device is installed in an aircraft has been described. However, a noise reduction device installed other than a moving body can also be used. For example, for a noise reduction device that reduces noise caused by vehicles passing through a road, traffic information is input to the noise reduction device as environmental information, and when the road is congested and noisy, the amount of computation is increased and the road is If the noise is low, the amount of calculation can be reduced to reduce the power consumption of the noise reduction device. Needless to say, in the case where the increase / decrease in the calculation amount is realized by the increase / decrease in the number of microphones, it is possible to extend the life of the apparatus and reduce the probability of abnormal operation.

  The noise reduction device according to the present invention can provide an effective noise reduction device with low power consumption according to changes in the installation environment of the noise reduction device. Therefore, it is useful as a noise reduction device installed in a place where the installation environment changes, particularly as a noise reduction device in a use space having noise such as an aircraft, a train, or a car.

The block diagram which shows the basic composition of the noise reduction apparatus in embodiment of this invention Plan view showing the installation environment of the noise reduction device Plan view showing details of the installation environment of the noise reduction device Block diagram showing the detailed configuration of the noise reduction device Plan view showing a specific example when the noise reduction device is installed in an aircraft seat Graph of aircraft noise characteristics at high and low altitudes Plan view showing an operation example of the noise reduction device State transition diagram of the noise reduction device when changing the number of noise microphones based on altitude information State transition diagram of the noise reduction device when changing the number of TAPs based on altitude information

Explanation of symbols

10, 10a-10m Noise detection means (noise microphone)
11 Noise control means 12, 12a, 12b Control sound output means (speaker)
13 Environmental characteristic input means 14 Residual sound detection means (residual sound microphone)
100 Aircraft 101a, 101b Wings 102a, 102b Engine 103a, 103b, 103c Seat row 105, 630 Seat 300 Noise reduction device 301 User 302 Ear 310, NS1a, NS1b, NS1c, NS2a, NS2b, NS2c, NS2d, NS2e Noise source Noise arrival path 310α Noise spread angle 331, 335 A / D converter 332 Digital filter 333 Control unit 334 D / A converter 650 Shell s810, s910 Environmental characteristic reading state s820, s920 Altitude change judgment state s830 Number of noise microphones used Change / filter read status s930 Tap number change / filter read status A, B, C Guest room D Space

Claims (9)

A device installed on a moving body, comprising: a noise detection means for detecting noise emitted from a noise source; a noise control means for generating a control sound for reducing noise detected by the noise detection means; A noise reduction apparatus comprising: control sound output means for outputting control sound; and environmental characteristic input means for inputting environmental characteristics of the mobile body, wherein the control sound is optimized based on the environmental characteristics. 2. The noise according to claim 1, further comprising a residual sound detection unit configured to detect a residual sound obtained by reducing the noise with the control sound, wherein the control sound is optimized based on the environmental characteristics and the residual sound. Reduction device. The noise reduction device according to claim 1, wherein the environmental characteristic is altitude information of the moving body. The noise reduction device according to claim 1, wherein the environmental characteristic is speed information of the moving body. The noise reduction device according to claim 1, wherein the environmental characteristic is route information of the moving body. The number of the noise detection means used when the altitude information is low is n, the number of the noise detection means used when the altitude is high, and the number of the noise detection means used when the altitude is low is 4. The noise reduction device according to claim 3, wherein the noise reduction device is optimized so as to be smaller (n <m) than the number of noise detection means used in the previous period at a high altitude. The noise control means is composed of a digital filter, and when the altitude information is low altitude, the number of taps of the digital filter is p, when the altitude information is high, the number of taps of the digital filter is q, and when the altitude information is low altitude 4. The noise reduction device according to claim 3, wherein the number of taps of the digital filter is optimized (p <q) to be less than the number of taps of the previous digital filter when the altitude is high. When the speed information is high, the number of the noise detection means used is a, the number of the noise detection means used when the speed information is low, and the number of the noise detection means used when the speed is high is low. 5. The noise reduction device according to claim 4, wherein the noise reduction device is optimized so as to be smaller than the number of the first-stage noise detection means (a <b). The noise control means is composed of a digital filter. The number of taps of the digital filter when the speed information is high is s, the number of taps of the digital filter is low when the speed information is low, and the number of taps of the digital filter is high when the speed information is high. The noise reduction device according to claim 4, wherein the noise reduction device is optimized so as to be smaller (s <t) than the number of taps of the previous digital filter when the number of taps is low.

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