Sound system and in-vehicle communication support system

Abstract

The invention provides a sound system and an in-vehicle communication support system, which can suppress the disadvantage of ultrasonic radiation through a parametric speaker and increase the reproduction level of audible sound. Ultrasonic waves, which have been amplitude-modulated with audible sound emitted from a parametric speaker (1), are incident on an audible sound collector (2) with high directivity. The audible sound collector (2) attenuates incident ultrasonic waves and ultrasonic waves in audible sound self-demodulated from the ultrasonic waves, reflects the audible sound, and collects sound at a position in the vicinity of a user. The audible sound collector (2) can be configured from a reflector (21) having a reflecting surface that is a paraboloid of revolution and a sound absorber (22) that absorbs sound of ultrasonic waves, and the sound absorber (22) can be configured using an inverter tube (221) and a sound absorbing material using a photonic crystal.

Description

Technical Field

[0001] This invention relates to a technique for partial reproduction using parametric loudspeakers. Background Technology

[0002] As a technique for partial reproduction using a parametric loudspeaker, there is a known parametric loudspeaker technique that uses an audible sound signal to amplitude modulate an ultrasonic signal, and uses the amplitude-modulated signal to drive a highly directional ultrasonic transducer array to emit ultrasonic waves, thereby reproducing audible sound as radially self-demodulated audible sound during the propagation of ultrasonic waves in the air, with highly directional reproduction (e.g., Patent Document 1).

[0003] In addition, the following techniques are known: making the direction of the directivity of such a parameter loudspeaker variable, and controlling the direction of the directivity (e.g., Patent Document 2).

[0004] In addition, there are known technologies that use a reflector with a rotating parabolic or rotating elliptical surface as the reflector to reflect ultrasonic waves that are amplitude modulated and emitted using audible sound signals, thereby collecting the sound at a location near the user and reproducing the audible sound (e.g., Patent Documents 3 and 4).

[0005] In addition, as a technology related to this invention, sound-absorbing materials made of phononic crystals that absorb only the ultrasonic components emitted from the parametric loudspeaker are known (Non-Patent Document 1).

[0006] In addition, as a technology related to the present invention, the following technologies are known: ultrasonic sound-absorbing materials having a bubble structure (e.g., Patent Document 5), and technologies for absorbing noise in the resonant frequency band of the phase inverter tubes by arranging closed tubes with one side open and the other closed (e.g., Patent Document 6).

[0007] [Existing Technical Documents]

[0008] [Patent Documents]

[0009] Patent Document 1: Japanese Patent Application Publication No. 2011-234248

[0010] Patent Document 2: Japanese Patent Application Publication No. 2004-349816

[0011] Patent Document 3: Japanese Patent Application Publication No. 2003-158788

[0012] Patent Document 4: Japanese Patent Application Publication No. 7-107588

[0013] Patent Document 5: Japanese Utility Model Registration No. 3128029

[0014] Patent Document 6: Japanese Patent Application Publication No. 07-302087

[0015] [Non-patent literature]

[0016] Non-Patent Literature 1: Sugawara Akiko, Li Xiaozhen, Sakamoto Shinichi, Takeoka Seito, “Research on the Reduction of Ultrasonic Waves in the Measurement of Architectural Acoustic Characteristics Using Parametric Loudspeakers as Sound Sources”, Proceedings of the Autumn Research Presentation of the Acoustical Society of Japan, pp. 1061-1062, September 2017 Summary of the Invention

[0017] In the reproduction of audible sound via ultrasound using a parametric loudspeaker, the following problems generally need to be addressed.

[0018] That is, there is a problem that the audible sound reproduced is of a lower level than the ultrasonic level, and that ultrasonic waves of a higher level are emitted to the user and reproduced at the destination of ultrasonic wave reflection.

[0019] The problem of audible sound level can be improved by setting up a reflector that collects the ultrasonic waves emitted from the parameter speaker towards a location near the user. However, if this is done, it may result in the emission of ultrasonic waves of a higher level towards the user, and thus create a problem with the reproduction of audible sound at the reflection destination based on the higher level ultrasonic waves.

[0020] Therefore, the technical problem of the present invention is to suppress the adverse effects caused by the emission of ultrasonic waves and increase the level of audible sound reproduction when reproducing audible sound via ultrasonic waves using a parametric loudspeaker.

[0021] To achieve the aforementioned technical problem, the present invention provides an audible sound collector for a parametric loudspeaker that emits ultrasonic waves modulated with audible sound as emitted sound waves. The audible sound collector includes a reflector and a sound absorber. The reflector has a reflecting surface that reflects sound waves incident from the same direction as the incident sound waves. Furthermore, the sound absorber is positioned closer to the direction of the incident sound waves than the reflecting surface of the reflector, causing attenuation of the ultrasonic component of the emitted sound waves reaching the reflecting surface. The reflecting surface of the reflector reflects the audible component of the emitted sound waves that is demodulated and incident on the audible sound collector, focusing the sound at a predetermined sound collection position.

[0022] In this audio system, the reflective surface of the reflector may be a paraboloid of revolution.

[0023] Alternatively, in this audio system, the sound absorber may be a sound-absorbing material that uses phononic crystals to absorb ultrasonic waves.

[0024] Alternatively, in this audio system, the sound absorber may have multiple closed-tube bass reflex ports that absorb ultrasonic waves.

[0025] Alternatively, in this audio system, the sound-collecting position may be located in a direction deviating from the direction of incidence of the emitted sound wave, as observed from the audible sound collector.

[0026] In addition, the present invention also provides an in-vehicle communication support system for automobiles, which includes the above-described audio system. This in-vehicle communication support system includes a microphone that collects the voice of a user seated in the first seat of the automobile, and a parametric speaker that emits ultrasonic waves modulated by the voice collected by the microphone as emitted sound waves. The audible sound collector of the audio system collects the audible sound components at a location near a user seated in the second seat of the automobile.

[0027] According to the above-described sound system, by using a sound absorber to suppress ultrasonic components from reaching the reflecting surface through an audible sound collector, and by focusing the audible sound components at the focusing location through the reflecting surface, it is possible to increase only the level of audible sound. Therefore, it is possible to suppress the problem of reproducing audible sound at the reflection destination based on ultrasonic waves that are emitted to the user at a higher level.

[0028] [Invention Effects]

[0029] As described above, according to the present invention, when reproducing audible sound via ultrasound using a parametric loudspeaker, it is possible to suppress the adverse effects caused by the emission of ultrasound and to increase the reproduction level of audible sound. Attached Figure Description

[0030] Figure 1 This is a diagram showing the structure of an audio system according to an embodiment of the present invention.

[0031] Figure 2 This is a diagram illustrating a structural example of an audible sound collector according to an embodiment of the present invention.

[0032] Figure 3 This is a diagram illustrating a structural example of an audible sound collector according to an embodiment of the present invention.

[0033] Figure 4 This is a diagram illustrating an application example of an audio system according to an embodiment of the present invention.

[0034] Figure 5 This is a diagram illustrating an application example of an audio system according to an embodiment of the present invention.

[0035] Figure 6 This is a diagram illustrating another structural example of an audio system according to an embodiment of the present invention. Detailed Implementation

[0036] The embodiments of the present invention will be described below.

[0037] Figure 1 This describes the structure of the audio system in this embodiment.

[0038] As shown in the figure, the audio system has a speaker 1 and an audible sound collector 2.

[0039] The speaker 1 includes: an oscillator 11 that generates an AC signal, i.e., a carrier signal, at a frequency (e.g., 40 kHz) of the ultrasonic band; a modulator 12 that modulates the carrier signal amplitude using an input audible sound signal; a drive unit 13; and an ultrasonic transducer array 14. The drive unit 13 drives the ultrasonic transducer array 14 using a drive signal that amplifies the modulation signal modulated by the modulator 12 and adjusts the phase for directional control, so that the amplitude-modulated ultrasonic waves are emitted from the ultrasonic transducer array 14 in a predetermined directional direction with high directivity.

[0040] The direction of the amplitude-modulated ultrasonic waves emitted from the ultrasonic transducer array 14 is the direction of the audible sound collector 2, and the amplitude-modulated ultrasonic waves and the audible sound that is self-demodulated from the ultrasonic waves in space are incident on the audible sound collector 2.

[0041] The audible sound collector 2 attenuates the incident ultrasonic waves and the ultrasonic waves in the audible sound, reflects the audible sound, and concentrates the sound at the sound collection position CP near the user.

[0042] Figure 2 This shows a structural example of an audible sound collector 2.

[0043] like Figure 2 As shown in a, the audible sound collector 2 includes: a reflector 21 with a reflective surface having a rotating parabolic surface and a sound absorber 22 for absorbing ultrasonic waves.

[0044] Here, Figure 2 'a' represents the shape of the audible sound collector 2 as viewed from the opening side in the direction of the rotation axis of the parabola of revolution. Figure 2 The 'b' represents the shape of the audible sound collector 2 as viewed from a direction perpendicular to the axis of rotation of the parabolic sphere. Figure 2 c represents Figure 2 The cross section of line AA of a.

[0045] As shown in the figure, the reflector 21 has a parabolic antenna shape, and a sound absorber 22 is arranged in the concave part on the inner side of the reflector to cover the reflector.

[0046] The sound absorber 22 has the functions of absorbing incident ultrasonic waves or reflecting them in a way that prevents them from reaching the reflecting surface, and allowing incident audible sound to pass through.

[0047] Therefore, such as Figure 2 As shown in d, the audible sound collector 2 can reflect only the incident ultrasonic waves and the audible sound from the audible sound to the sound collection point CP near the user and amplify it, increasing the volume of the audible sound that the user can hear, and can suppress the radiation of ultrasonic waves to the user.

[0048] For example, the gain of a parabolic antenna is,

[0049] G=(πd / λ) 2 e A

[0050] Where d: diameter, λ: wavelength, e A The gain (aperture efficiency) is the coefficient; therefore, if the diameter of the reflecting surface is set to 15cm, the gain for audible sound at 1kHz becomes GA = 1.92e. A .

[0051] Furthermore, without the sound absorber 22, the gain of the 40kHz ultrasonic wave, i.e., the carrier wave, is GC = 3073.58e. A An extremely large ultrasonic wave, amplified 1600 times (32dB) compared to audible sound, is emitted toward the user. However, in this embodiment, with the sound absorber 22 provided, the emission of such a greatly amplified ultrasonic wave is suppressed.

[0052] Furthermore, in this embodiment, similar to the biased parabolic antenna, the collection point CP of the audible sound collector 2 is set to a direction that is tilted away from the incident direction of the modulated ultrasonic wave, so as not to obstruct the incident of the user-modulated ultrasonic wave onto the audible sound collector 2.

[0053] In addition, as such a sound absorber 22, for example, a sound-absorbing material utilizing phononic crystals can be used.

[0054] When using phononic crystals, such as Figure 2 As shown in Figure e, if the period of the structure is set to a and the incident angle of the sound wave is set to θ, then the center frequency fc of the sound wave reflection band is fc when C is the speed of sound.

[0055] fc = nC / (2acosθ)

[0056] n = 1, 2, 3, ...

[0057] Therefore, for example, if the speed of sound is set to C and 340 m / s, and the absorber 22 is configured with a = 4 mm and an incident angle θ of 0°, then when n = 1, it can be set to fc = 42.5 kHz.

[0058] Therefore, with regard to the sound absorber 22, when using a 40kHz carrier wave, it is possible to use a sound-absorbing material utilizing phononic crystals to reflect the ultrasonic waves incident on the audible sound collector 2 in a manner that does not reach the reflecting surface.

[0059] Furthermore, when the incident angle θ is not 0°, by setting the structure period a to approximately 40 kHz with nC / (2acosθ), it is possible to reflect the ultrasonic waves incident on the audible sound collector 2 without reaching the reflecting surface when using a 40 kHz carrier wave.

[0060] It is possible to obtain the same center frequency fc of the sound wave reflection band.

[0061] Here, the sound absorber 22 is not limited to the sound-absorbing material using phononic crystals; it can be any material that absorbs ultrasonic waves. It can also be any sound-absorbing material, such as a sound-absorbing material with a bubble structure that absorbs ultrasonic waves, other ultrasonic materials, etc.

[0062] Furthermore, the configuration of the sound absorber 22 can be any configuration that covers the reflective surface when viewed from the incident side; it can be... Figure 2 The configuration shown in f is a recess located only on the opening side of the inner side of the reflective surface. Figure 2 The configuration shown in g is positioned in front of the reflector 21, etc.

[0063] In addition, as a sound absorber 22, a sound absorber 22 that utilizes a closed-tube bass reflex tube can be used.

[0064] Here, the shape of the audible sound collector 2, viewed from the open side in the direction of the rotation axis of the parabolic sphere, is shown when a sound absorber 22 using a closed-tube bass reflex tube is employed. Figure 3 The shape of the audible sound collector 2, as viewed from a direction perpendicular to the axis of rotation of the parabolic sphere, is shown in Figure 1. Figure 3 b, will Figure 3 The cross section of line AA of a is shown in Figure 3 c.

[0065] As shown in the figure, the audible sound collector 2 has the following structure: the sound absorber 22, which is formed by arranging closed-tube phase inverters 221, is arranged with an opening that covers the recessed part inside the reflective surface of the reflector 21.

[0066] like Figure 3As shown in diagram d, if the length L and diameter a of the closed tube are determined, then the length L of the closed tube with natural vibration of wavelength λ is L = λ / 4. Furthermore, the diameter a must be a ≤ 0.586λ relative to the wavelength λ to hold true. Taking the wavelength λ of a 40kHz carrier wave as the natural vibration, if the speed of sound C is set to 340m / s, then according to λ = C / fc, the length L of the tube is L = C / fc / 4 = 0.002125, approximately 2.1mm. Additionally, the diameter a ≤ 0.586λ = 0.004891, approximately 4.9mm or less, is acceptable.

[0067] Therefore, by using a sound absorber 22 consisting of phase-reflecting tubes 221 arranged with a length of approximately 2.1 mm and a diameter of less than 4.9 mm, ultrasonic waves incident on the audible sound collector 2 can be reflected in a manner that does not reach the reflecting surface.

[0068] Furthermore, when using a sound absorber 22 that utilizes a phase inverter 221, the configuration of the sound absorber 22 can be any configuration that covers the reflective surface when viewed from the incident side; it can also be... Figure 3 The configuration shown in figure e, positioned in front of reflector 21, Figure 3 The configuration shown in f is set up in a way that covers the reflective surface, etc.

[0069] The audio system of the present invention has been described above.

[0070] Such a sound system can be applied to a variety of systems.

[0071] Here, as an example, we show an application of the audio system to an ICC (In-Car Communication) system for voice-based communication between users inside a passenger car.

[0072] Figure 4 'a' represents the structure of the ICC system.

[0073] As shown in the figure, the ICC system includes multiple microphones 401, a selector 402, a signal processing unit 403, a parametric speaker group 404 including one or more parametric speakers 1, an ICC control unit 405, and multiple audible sound collectors 2. Here, the parametric speaker group 404 and the multiple audible sound collectors 2 form a structure corresponding to the above-described audio system.

[0074] In addition, such as Figure 5 As shown in a1, for example, multiple microphones 401 are arranged corresponding to each seat in the passenger vehicle, and are configured near the corresponding seat in a manner that picks up the voice of the user sitting in the corresponding seat. However, the microphones 401 may also be arranged to be shared by multiple seats, for example, one for each row of seats.

[0075] Additionally, the parametric speaker assembly 404 is, for example, located in the rear of the vehicle interior, and multiple audible sound collectors 2 are positioned corresponding to each seat, each located in front of its respective seat. Each audible sound collector 2 reflects the audible sound emitted from the parametric speaker assembly 404 towards itself, which is then self-demodulated from the ultrasonic waves after amplitude modulation using audible sound, and concentrates the sound towards the user seated in the corresponding seat.

[0076] Here, as Figure 5 As shown in a2, the parameter speaker group 404 and multiple audible sound collectors 2 can be configured in the interior ceiling.

[0077] Additionally, return to Figure 4 The ICC control unit 405 controls the following action according to the preset correspondence or the correspondence selected by the user: to emit ultrasonic waves with amplitude modulated by the sound input from one or more microphones 401 toward one or more audible silencers.

[0078] For example, when an ultrasonic wave, whose amplitude is modulated using the sound input from the i-th microphone 401, is emitted toward the j-th audible sound collector 2, the selector 402 causes the output of the i-th microphone 401 to be emitted as sound i to the signal processing unit 403. The signal processing unit 403 performs echo cancellation processing and gain adjustment on sound i and outputs it to the parameter speaker group 404. Then, in the parameter speaker 1 of the parameter speaker group 404, which has a directional direction in the direction of the j-th audible sound collector 2, the carrier wave of the ultrasonic wave is amplitude modulated using sound i and emitted toward the j-th audible sound collector 2.

[0079] Here, as a parameter loudspeaker 1 having a pointing direction in the direction of the j-th audible sound collector 2, parameter loudspeakers 1 that have a fixed pointing direction in the direction of each audible sound collector 2 can be prepared in advance. The parameter loudspeaker 1 having a pointing direction in the direction of the j-th audible sound collector 2 can be used. Alternatively, a parameter loudspeaker 1 that can change its pointing direction can be prepared. When an amplitude-modulated ultrasonic wave is emitted into the j-th audible sound collector 2, the pointing direction of the parameter loudspeaker 1 can be controlled in the ICC control unit 405 to be the direction of the j-th audible sound collector 2.

[0080] Similarly, when an ultrasonic wave, whose amplitude is modulated using the sound input from the i-th microphone 401, is emitted towards the j-th, k-th, m-th, n-th... audible sound collectors 2, the selector 402 emits the output of the i-th microphone 401 as sound i into the signal processing unit 403. The signal processing unit 403 performs echo cancellation processing and gain adjustment on sound i and outputs it to the parameter speaker group 404. Furthermore, in the four parameter speakers 1 of the parameter speaker group 404 that have a directional direction in the direction of the j-th, k-th, m-th, n-th... audible sound collectors 2, the sound i, which serves as the carrier wave of the ultrasonic wave, is amplitude modulated and emitted towards the j-th, k-th, m-th, n-th... audible sound collectors 2.

[0081] Here, as a parametric loudspeaker 1 having a directional direction in the direction of the j, k, m, n... audible sound collectors 2, parametric loudspeakers 1 with a fixed directional direction in the direction of each audible sound collector 2 can be prepared in advance. Using the parametric loudspeakers 1 with a directional direction in the direction of the j, k, m, n... audible sound collectors 2, multiple parametric loudspeakers 1 that can change their directional direction can also be prepared and used at the same time. When the j, k, m, n... audible sound collectors 2 emit amplitude-modulated ultrasonic waves, the directional direction of the multiple parametric loudspeakers 1 of the j, k, m, n... audible sound collectors 2 is controlled in the ICC control unit 405 to be the direction of the j, k, m, n... audible sound collectors 2.

[0082] Next, the actions of emitting the ultrasonic waves, whose amplitude has been modulated using the sounds input from the a, b, c, d... microphones 401, toward the j-th audible sound collector 2, and the actions of emitting the ultrasonic waves toward the j, k, m, n... audible sound collectors 2, are described above as follows: In the parameter loudspeaker 1, instead of the sound i input from the i-th microphone 401, the sound synthesized by the signal processing unit 403 from the sounds input from the a, b, c, d... microphones 401 is used to modulate the carrier wave of the ultrasonic waves.

[0083] Here, as described above, the number of parameter loudspeakers 1 required for parameter loudspeaker group 404 is, in the case of using parameter loudspeakers 1 that can change direction, the number of audible sound collectors 2 that are sometimes used simultaneously, and in the case of using parameter loudspeakers 1 with fixed direction, the number of audible sound collectors 2 that can be used regardless of whether they are used simultaneously.

[0084] However, it is also possible to use a speaker 1 with parameters that can be set to multiple variable directions. When multiple audible sound collectors 2 are used at the same time, the same speaker 1 can be shared for two or more audible sound collectors 2.

[0085] Furthermore, in such an ICC system, when the parametric speaker group 404 includes multiple parametric speakers 1, each parametric speaker 1 can also be configured in different positions. For example, as Figure 5 As shown in b, a parametric speaker 1 for an audible sound collector corresponding to the first row of seats can be installed at the rear of the first row of seats, a parametric speaker 1 for an audible sound collector corresponding to the second row of seats can be installed at the rear of the second row of seats, and a parametric speaker 1 for an audible sound collector corresponding to the third row of seats can be installed at the rear of the third row of seats.

[0086] Additionally, at least a portion of the audible sound collector 2 can also be configured in the seat, for example, as shown in... Figure 5 As shown in c1 and c2, the audible sound collector 2 corresponding to the second row of seats is installed in the headrest of the first row of seats, and the audible sound collector 2 corresponding to the third row of seats is installed in the headrest of the second row of seats.

[0087] Alternatively, it can be like Figure 5 As shown in c1, the parametric speaker group 404 is arranged at the front of the vehicle interior, and the audible sound collector 2 corresponding to each seat is arranged behind each seat. In the audible sound collector 2, the audible sound after the ultrasonic wave amplitude modulation by the audible sound emitted from the parametric speaker group 404 towards itself is reflected forward and collected towards the user sitting in the corresponding seat.

[0088] Furthermore, in this example, such as Figure 5 As shown in c2, an audible sound collector 2 corresponding to each seat is installed on the headrest of that seat.

[0089] Next, the structure of the audio system in this embodiment can also be configured as follows: Figure 6 As shown in a and b, the parametric speaker 1 and the audible sound collector 2 are configured coaxially, and the audible sound is collected at a position close to the user between the parametric speaker 1 and the audible sound collector 2.

[0090] Figure 6 Figure a illustrates a scenario where modulated ultrasonic waves are emitted towards the audible sound collector 2, bypassing the user. Figure 6 Figure b illustrates a scenario where a portion of the modulated ultrasonic wave is allowed to radiate toward the user and toward the audible sound collector 2.

[0091] exist Figure 6 In case b, regarding the level of audible sound that the user can hear, based on the smaller direct wave, it can be expected that the audible sound collected by the audible sound collector 2 will dominate. Furthermore, the ultrasonic waves emitted towards the user are also limited to a portion of the emitted ultrasonic waves.

[0092] Furthermore, in the above embodiments, the reflecting surface of the reflector 21 is set as a paraboloid of revolution, but the reflecting surface can also be set as a shape that can appropriately collect appropriate audible sound according to the incident angle and the expansion of the incident angle of the modulated ultrasonic wave. That is, the shape of the reflecting surface can be, for example, an elliptical surface of revolution or other concave surfaces.

[0093] [Explanation of Labels in the Attached Image]

[0094] 1…parameter loudspeaker, 2…audible sound collector, 11…oscillator, 12…modulator, 13…driver, 14…ultrasonic transducer array, 21…reflector, 22…sound absorber, 221…phase converter, 401…microphone, 402…selector, 403…signal processing unit, 404…parameter loudspeaker group, 405…ICC control unit.

Claims

1. A sound system comprising a parametric loudspeaker that emits ultrasonic waves modulated with audible sound as emitted sound waves, characterized in that, An audible sound collector is provided for the emitted sound waves emitted by the speaker with the specified parameters to be incident upon. The audible sound collector includes a reflector and a sound absorber. The reflector has a reflecting surface that reflects sound waves incident from the same direction as the incident direction of the emitted sound waves. The sound absorber is positioned on the side closer to the incident direction of the emitted sound wave than the reflective surface of the reflector, thereby attenuating the ultrasonic component of the emitted sound wave reaching the reflective surface. The reflective surface of the reflector will reflect the audible components of the emitted sound wave that are self-demodulated and incident on the audible sound collector, and concentrate the sound at the designated sound collection position.

2. The audio system according to claim 1, characterized in that, The reflector's reflective surface has the shape of a paraboloid of revolution.

3. The audio system according to claim 1, characterized in that, The sound absorber is a sound-absorbing material that uses phononic crystals to absorb ultrasonic waves.

4. The audio system according to claim 1, characterized in that, The sound absorber has multiple closed-tube phase inverters that absorb ultrasonic waves.

5. The audio system according to claim 1, characterized in that, The sound-collecting position is located in a direction deviating from the direction of incidence of the emitted sound wave when viewed from the audible sound collector.

6. An in-vehicle communication support system, installed in a car, characterized in that, have: The audio system according to any one of claims 1 to 5; and The microphone collects the voice of the user sitting in the first seat of the car. The speaker will emit ultrasonic waves modulated from the spoken sound collected by the microphone as the emitted sound waves. The audible sound collector of the audio system collects the audible sound components at a location near the user sitting in the second seat of the car.

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