Acoustic control device and acoustic control method

Abstract

To accurately cancel vibrations in an asymmetric R2R speaker.SOLUTION: In an audio amplifier of an embodiment, based on an input sound source signal, there are generated: a sounding side drive signal to drive a sounding side speaker; and a cancel side drive signal to drive a cancel side speaker that is provided such that the back surface of the sounding side speaker faces that of the cancel side speaker, the cancel side speaker having a physical property different from that of the sounding side speaker. In the audio amplifier, the phase of the cancel side drive signal is corrected according to parameters associated with the sound source signal.SELECTED DRAWING: Figure 4

Description

[[Technical Field]]

[0001] The present invention relates to an acoustic control apparatus and an acoustic control method. [[Background Art]]

[0002] A speaker has a structure that generates sound through air vibration caused by a diaphragm moving back and forth. At this time, due to the reaction of the movement, the magnetic circuit and the frame move to a not inconsiderable extent, so unnecessary vibration (distortion) occurs with respect to accurate diaphragm vibration. Furthermore, such unnecessary vibration may be transmitted to surrounding members fixed to the speaker, causing abnormal noise.

[0003] In contrast, a technique is known that suppresses vibration of the magnetic circuit by means of a weight attached to the back side of the magnetic circuit (see, for example, Patent Document 1).

[0004] Furthermore, an R2R (Rear to Rear) method is known in which opposing speakers of the same shape are driven with in-phase signals to cancel out vibration (see, for example, Non-Patent Document 1). Additionally, each speaker constituting the R2R method may be referred to as a unit. Further, two speakers configured by the R2R method may be referred to as R2R speakers.

[0005] According to the R2R method, driving vibration and air pressure fluctuation of the units can be canceled out with each other, and generation of abnormal noise from the housing can be prevented.

[0006] The R2R method also has other names such as "rear-facing structure", "Dual Opposed", and "Force Cancelling". Additionally, the R2R method may be employed in home speaker systems. [[Prior Art Documents]] [[Patent Documents]]

[0007] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2002-152884 [Non-patent literature]

[0008] [Non-Patent Document 1] Denso Ten, "TD316SWMK2", [online], [searched July 11, 2022], Internet (https: / / www.eclipse-td.com / products / td316swmk2 / index.html) [Overview of the project] [Problems that the invention aims to solve]

[0009] To miniaturize R2R speakers, one approach is to make the two speakers have different shapes. In this case, the two speakers are called asymmetric R2R speakers.

[0010] However, in asymmetric R2R speakers, the physical characteristics of the speakers differ from each other, which can sometimes prevent accurate vibration cancellation. [Means for solving the problem]

[0011] To solve the above-mentioned problems and achieve the objective, the sound control device according to the present invention includes a controller that generates a speaker drive signal based on a sound source signal. The controller generates a first drive signal for driving a first speaker and a second drive signal for driving a second speaker which is provided so that its rear faces the first speaker and has different physical characteristics from the first speaker, based on the input sound source signal. The controller corrects the phase of the second drive signal according to a parameter associated with the volume of the sound source signal. [Effects of the Invention]

[0012] According to the present invention, vibrations can be canceled with high precision in an asymmetric R2R speaker. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a diagram illustrating an arrangement example of speakers. [Figure 2] Figure 2 is a diagram illustrating a configuration example of an asymmetric R2R speaker. [Figure 3] Figure 3 is a diagram illustrating a configuration example of an audio system. [Figure 4] Figure 4 is a diagram illustrating a configuration example of an acoustic signal processing unit. [Figure 5] Figure 5 is a diagram illustrating a phase difference between the sounding side and the cancellation side. [Figure 6] Figure 6 is a diagram illustrating a gain difference between the sounding side and the cancellation side. [Figure 7] Figure 7 is a diagram illustrating an example of phase correction parameters. [Figure 8] Figure 8 is a flowchart illustrating a processing flow of the acoustic signal processing unit. [Figure 9] Figure 9 is a diagram illustrating a configuration of a conventional R2R speaker. DESCRIPTION OF EMBODIMENTS

[0014] First, a conventional R2R speaker will be described with reference to FIG. 9. FIG. 9 is a diagram illustrating a configuration of a conventional R2R speaker.

[0015] As illustrated in FIG. 9, the R2R speaker 40a is formed by coupling a speaker 41a and a speaker 42a back to back. The term "back to back" means that members on the side opposite to the diaphragm that emits sound are bonded to each other.

[0016] Conventional R2R speakers have a problem that the overall size of the device increases. Additionally, in conventional R2R speakers, the two speakers need to have the same shape, which reduces the degree of freedom in design.

[0017] In the present embodiment, an asymmetric R2R speaker is used for the purpose of solving the problems of conventional R2R speakers.

[0018] In an asymmetric R2R speaker, the physical characteristics of the two speakers can be different from each other. For example, in an asymmetric R2R speaker, one of the speakers can be smaller compared to a conventional R2R speaker.

[0019] On the other hand, in asymmetric R2R speakers, because the physical characteristics of the two speakers are different, simply inputting the same drive signal to both speakers may not be able to cancel out vibrations.

[0020] This is because the two speakers differ in shape, weight, material properties, etc. Shape, weight, and material properties are just a few examples of physical characteristics. For example, speaker 41a and speaker 42a differ in at least one of the following physical characteristics: shape, weight, and material properties.

[0021] Furthermore, as mentioned above, in an asymmetric R2R speaker, one speaker is smaller than the other. For example, during miniaturization, the structure and materials of the two speakers may differ from each other, resulting in different physical characteristics for the two speakers.

[0022] For example, if the same drive signal is input to two speakers of different weights, differences will occur in the vibration period and amplitude of the two speakers, and this difference may cause unwanted vibrations and abnormal noises.

[0023] Furthermore, experiments have shown that the differences in the behavior of the two speakers in an asymmetric R2R speaker system manifest in different ways depending on the specified volume.

[0024] In this embodiment, one objective is to suppress the effects of differences in behavior caused by such differences in volume.

[0025] The embodiments of the acoustic control device and acoustic control method disclosed herein will be described in detail below with reference to the attached drawings. However, the present invention is not limited to the embodiments described below.

[0026] In this embodiment, the asymmetric R2R speaker is mounted on a vehicle. However, the asymmetric R2R speaker of this embodiment may also be installed on a mobile device other than a vehicle, inside a building, or outdoors.

[0027] Figure 1 shows an example of speaker arrangement. As shown in Figure 1, vehicle 1 is equipped with speakers 31, 32, 33, 34, 35, 36, 37, and 40.

[0028] Speaker 31 is located on the left side of the front seat (channel: FrontL). Speaker 32 is located on the right side of the front seat (channel: FrontR). Speaker 33 is located on the left side of the rear seat (channel: RearL). Speaker 34 is located on the right side of the rear seat (channel: RearR). Speaker 35 is located on the left front door (channel: FdoorL). Speaker 36 is located on the right front door (channel: FdoorR). Speaker 37 is located in the center of the front seat (channel: Center).

[0029] Speaker 40 is located in the center of the rear seat. Speaker 40 is an asymmetric R2R speaker. Speaker 40 may also function as a woofer to output low-frequency sounds. Note that the position of speaker 40 is not limited to the center of the rear seat, but may be any position in the vehicle 1.

[0030] Here, one side of the asymmetrical speaker is called the sound-generating side. The side opposite the sound-generating side of the asymmetrical speaker is called the cancellation side. Speaker 40 corresponds to two channels: woofer1 on the sound-generating side and woofer2 on the cancellation side.

[0031] Vehicle 1 is also equipped with a playback device 10 and an audio amplifier 20. The playback device 10 inputs the sound playback signal to the audio amplifier 20. Based on the playback signal, the audio amplifier 20 transmits signals to output sound to each speaker. The playback device 10 and the audio amplifier 20 may be separate devices or they may be integrated into a single unit.

[0032] Furthermore, the signal output by the audio amplifier 20 is called a drive signal because it is a signal used to drive the speakers.

[0033] The playback device 10 can be any device that functions as a sound source, such as a car navigation system, a dashcam, a car audio system, or a smartphone.

[0034] The audio amplifier 20 processes the playback signal using methods such as FIR (Finite Impulse Response), IIR (Infinite Impulse Response), filtering, mixing, noise reduction, and amplification.

[0035] Furthermore, the audio amplifier 20 transmits a drive signal to the speaker 40, which is an asymmetric R2R speaker, that can accurately cancel vibrations. The drive signal transmitted to the speaker 40 will be explained in detail later.

[0036] The audio amplifier 20 is an example of an acoustic control device and performs an acoustic control method.

[0037] Here, we will explain the configuration of speaker 40 using Figure 2. Figure 2 is a diagram showing an example of an asymmetric R2R speaker configuration.

[0038] As shown in Figure 2, the speaker 40 has a sound-generating speaker 41 and a cancellation-side speaker 42. A portion of the sound-generating speaker 41 and the cancellation-side speaker 42 are housed in the enclosure 45. Also, as shown in Figure 2, the back of the sound-generating speaker 41 faces the back of the cancellation-side speaker 42.

[0039] The sound-generating speaker 41 comprises a voice coil 411, a magnetic circuit 412, a diaphragm 413, and a coupling part 414. The cancellation-side speaker 42 comprises a voice coil 421, a magnetic circuit 422, and a coupling part 424.

[0040] In this embodiment, the cancellation-side speaker 42 does not have a diaphragm. However, the cancellation-side speaker 42 may have a diaphragm.

[0041] Even if the canceling speaker 42 does not have a diaphragm, it generates vibrations in response to the drive signal. The canceling speaker 42 cancels out the vibrations of the resonating speaker 41 with these vibrations.

[0042] Furthermore, the coupling portion 414 and the coupling portion 424 are made of metal or resin or the like, and they vibrate together with the voice coil 411 and the voice coil 421, respectively.

[0043] The connecting parts 414 and 424 do not need to be in close contact as shown in Figure 2. For example, the connecting parts 414 and 424 may be connected by a shaft, similar to the configuration shown in Non-Patent Document 1. Alternatively, the connecting parts 414 and 424 may be pistons provided opposite each other within the cylinder. In this case, vibrations are canceled out by the air pressure in the space between the pistons.

[0044] The playback device 10 and the audio amplifier 20 constitute the audio system 2. The configuration of the audio system 2 will be explained using Figure 3. Figure 3 is a diagram showing an example of the configuration of the audio system.

[0045] As shown in Figure 3, the playback device 10 inputs playback signals from multiple channels to the audio amplifier 20. The audio amplifier 20 outputs drive vibrations for multiple channels corresponding to each speaker.

[0046] The number of input channels and output channels of the audio amplifier 20 may be the same or different. The number of input channels and output channels of the audio amplifier 20 may also be just one.

[0047] The audio amplifier 20 includes an audio signal processing unit 21 and a P-IC (power amplifier IC) 22. The audio signal processing unit 21 performs processing such as filtering on the playback signal. The P-IC 22 amplifies the processed playback signal and outputs it to each speaker as a drive signal.

[0048] For example, the acoustic signal processing unit 21 is implemented by the computer's CPU acting as a controller, reading and executing a program stored in ROM (Read Only Memory). The acoustic signal processing unit 21 is an example of a controller that generates speaker drive signals based on sound source signals. The speaker drive signals are the drive signals that the acoustic signal processing unit 21 outputs to each speaker. Furthermore, the controller may implement not only the acoustic signal processing unit 21, but also both the acoustic signal processing unit 21 and the P-IC 22.

[0049] Furthermore, the controller may be a microcontroller, DSP (Digital Signal Processor), ECU (Electronic Control Unit), FPGA (Field Programmable Gate Array), GPU (Graphics Processing Unit), SoC (System on a Chip), etc.

[0050] Furthermore, the controller may be a single processor or a multi-processor configuration. Alternatively, the controller may be a multi-core configuration having multiple cores within a single chip connected by a single socket.

[0051] The configuration of the acoustic signal processing unit 21 will be explained using Figure 4. Figure 4 is a diagram showing an example of the configuration of the acoustic signal processing unit.

[0052] As shown in Figure 4, the acoustic signal processing unit 21 includes a VOL adjustment unit 211, a drive signal generation unit 212, and a correction unit 213. The acoustic signal processing unit 21 also stores correction parameters 214.

[0053] The VOL adjustment unit 211 adjusts the volume of the sound output from the speaker based on the VOL operation. For example, the VOL operation is the volume set by the user or by automatic control. For example, the VOL operation is expressed as a discrete value in dB. For example, the VOL operation may be an approximation of a continuous value set by a stepless dial to a discrete value.

[0054] The drive signal generation unit 212 adjusts the level of sound output from the speaker for each frequency band. The drive signal generation unit 212 is, for example, an equalizer. The drive signal generation unit 212 outputs a sound-activating drive signal and a cancellation drive signal.

[0055] The sound-activating drive signal and the cancellation drive signal output by the drive signal generation unit 212 may be the same.

[0056] Thus, the drive signal generation unit 212 generates, based on the input playback signal, a sound-generating drive signal for driving the sound-generating speaker 41, and a cancellation-side drive signal for driving the cancellation-side speaker 42, which is positioned so that its rear surfaces face the sound-generating speaker 41 and has different physical characteristics from the sound-generating speaker 41. For example, the different physical characteristics of the sound-generating speaker 41 and the cancellation-side speaker 42 are at least one of the following: shape, weight, and material properties.

[0057] The playback signal is an example of a sound source signal. The sound-generating speaker 41 is an example of a first speaker. The cancellation-side speaker 42 is an example of a second speaker. The sound-generating drive signal is an example of a first drive signal. The cancellation-side drive signal is an example of a second drive signal.

[0058] In this embodiment, the cancellation-side drive signal is corrected, but the ringing-side drive signal may also be corrected, or both the ringing-side drive signal and the cancellation-side drive signal may be corrected in different ways.

[0059] The correction unit 213 corrects the cancellation-side drive signal output from the drive signal generation unit 212. The correction unit 213 corrects at least one of the phase and gain of the cancellation-side drive signal.

[0060] Here, as shown in Figure 5, when the same drive signal is input to both the sound-generating speaker 41 and the cancellation-side speaker 42, the phase of vibration of each speaker differs in a specific frequency band. Figure 5 is a diagram showing the phase difference between the sound-generating and cancellation-side speakers.

[0061] Furthermore, the nature of the phase difference varies depending on the frequency band. This is because the physical characteristics of the sound-generating speaker 41 and the cancellation-side speaker 42 are different from each other.

[0062] Figure 5 shows the phase of vibrations generated from each speaker when a drive signal corresponding to a volume of 1W is input.

[0063] In the example shown in Figure 5, the phases of the sound-generating speaker 41 and the cancellation-side speaker 42 are roughly in sync in the frequency band above approximately 60 Hz. In contrast, in the frequency band between 25 Hz and 60 Hz, the phase of the cancellation-side speaker 42 is higher than that of the sound-generating speaker 41. On the other hand, in the frequency band below 25 Hz, the phase of the cancellation-side speaker 42 is lower than that of the sound-generating speaker 41.

[0064] Similarly, as shown in Figure 6, when the same drive signal is input to both the resonating speaker 41 and the canceling speaker 42, the vibration gain of each speaker differs in a specific frequency band. Figure 6 shows the difference in gain between the resonating and canceling sides.

[0065] Furthermore, the nature of the gain difference varies depending on the frequency band. This is because, as with the phase difference, the physical characteristics of the resonating speaker 41 and the canceling speaker 42 are different from each other.

[0066] Figure 6 shows the vibration gain generated by each speaker when a drive signal corresponding to a volume of 1W is input.

[0067] In the example shown in Figure 6, a gain difference is observed between the sound-generating speaker 41 and the cancellation-side speaker 42 in the 10Hz to 200Hz frequency band.

[0068] Note that the experimental results shown in Figures 5 and 6 were obtained by inputting the drive signal without coupling each speaker.

[0069] Furthermore, the nature of the differences in phase and gain between the resonating and canceling sides, as shown in Figures 5 and 6, changes depending on both volume and bandwidth.

[0070] Therefore, the correction unit 213 corrects the phase or gain of the cancellation-side drive signal according to predetermined parameters based on the volume (VOL). The parameters are stored as correction parameters 214.

[0071] Figure 7 shows an example of phase correction parameters. As shown in Figure 7, the correction parameter 214 includes parameters for each volume (VOL). The parameters include "Correction EQParam" and "Correction Gain".

[0072] "Correction EQParam" is a parameter for correcting the phase. "fc=25,Q=2.0,Type=Allpass,2nd" means that equalization is performed using a bi-order all-pass filter with a center frequency of 25Hz and a Q value (Q width) of 2.0.

[0073] For example, if the volume control for the acoustic signal processing unit 21 is set to "-1dB", the correction unit 213 equalizes the canceling drive signal according to the parameters "fc=25, Q=2.0, Type=Allpass, 2nd".

[0074] In this way, the correction unit 213 corrects the phase of the cancellation-side drive signal according to a parameter associated with the volume of the playback signal. This improves the accuracy of the cancellation even when the nature of the phase difference between the vibrations of the resonating side and the cancellation side changes depending on the volume.

[0075] Specifically, as described above, the correction unit 213 acquires the type of filter, center frequency, and Q value associated with the volume as parameters, and corrects the phase of the cancellation-side drive signal by performing equalization according to these parameters.

[0076] Furthermore, "Correction Gain" represents the amount of increase or decrease in gain. For example, if the VOL operation on the acoustic signal processing unit 21 is "-1dB", the correction unit 213 reduces the gain of the cancellation-side drive signal by 1.6dB.

[0077] In this way, the correction unit 213 further corrects the gain of the cancellation-side drive signal according to the parameters. This makes it possible to improve the accuracy of the cancellation even when the manner of the difference in vibration gain between the resonating side and the cancellation side changes depending on the volume.

[0078] The correction unit 213 may correct both the phase and the gain, or it may correct either one of them.

[0079] Furthermore, the volume may be set by the user. In this case, the correction unit 213 acquires a parameter associated with the volume set by the user for the playback signal. This prevents a decrease in the accuracy of the cancellation even if the user makes an unexpected change in volume.

[0080] Alternatively, the correction unit 213 may receive the volume level output from the sound-generating speaker 41 as feedback without acquiring the VOL operation, estimate the volume from the received sound, and correct the cancellation-side acoustic signal based on the estimated volume.

[0081] Figure 8 illustrates the processing flow of the acoustic signal processing unit. Figure 8 is a flowchart showing the processing flow of the acoustic signal processing unit.

[0082] As shown in Figure 8, first, the acoustic signal processing unit 21 receives the VOL operation and the playback signal input (step S101). The VOL operation is a numerical value indicating the volume set by the user, for example.

[0083] Next, the acoustic signal processing unit 21 adjusts the volume of the playback signal based on the VOL operation (step S102). The acoustic signal processing unit 21 also equalizes the playback signal and generates drive signals for the sound-generating and cancellation sides of the asymmetric R2R speaker (step S103). For example, the acoustic signal processing unit 21 performs equalization on the playback signal.

[0084] Next, the acoustic signal processing unit 21 acquires correction parameters corresponding to the VOL operation (step S104). The correction parameters for each VOL operation are stored in the correction parameter 214.

[0085] The acoustic signal processing unit 21 corrects the drive signal on the cancellation side according to the parameters (step S105). The acoustic signal processing unit 21 corrects the phase, gain, or both of the drive signal on the cancellation side.

[0086] Then, the acoustic signal processing unit 21 transmits the drive signal for the sounding side to the sounding side speaker 41 and transmits the corrected drive signal for the cancellation side to the cancellation side speaker 42 (step S106).

[0087] The acoustic signal processing unit 21 drives the sound-generating speaker 41 based on the sound-generating drive signal, and also drives the cancellation-side speaker 42 based on the corrected cancellation-side drive signal.

[0088] As described above, the audio amplifier 20 according to this embodiment generates a sound-generating drive signal for driving the sound-generating speaker 41, and a cancellation-side drive signal for driving the cancellation-side speaker 42, which is provided so that its rear faces are opposite to the sound-generating speaker 41 and has different physical characteristics from the sound-generating speaker 41. The audio amplifier 20 corrects the phase of the cancellation-side drive signal according to parameters associated with the sound source signal.

[0089] As a result, the audio amplifier 20 can accurately cancel vibrations in an asymmetric R2R speaker.

[0090] Furthermore, according to this embodiment, the shape of the cancellation-side speaker 42 can be changed, miniaturized, and lightened, thereby increasing the design flexibility of the asymmetric R2R speaker.

[0091] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and equivalents. [Explanation of symbols]

[0092] 1 vehicle 10 Playback device 20 Audio Amplifiers 31, 32, 33, 34, 35, 36, 37, 40 Speakers 41. Speaker on the side that produces sound 42 Cancelling speaker 45 cabinets 211 VOL adjustment section 212 Drive signal generation unit 213 Correction Unit 214 Correction Parameters 411, 421 voice coil 412, 422 Magnetic Circuits 413 Diaphragm 414, 424 joint

Claims

1. It includes a controller that generates a speaker drive signal based on the sound source signal. The aforementioned controller, Based on the sound source signal, a first drive signal is generated to drive a first speaker, and a second drive signal is generated to drive a second speaker which is provided so that its rear surfaces face the first speaker and which has different physical characteristics from the first speaker. The phase of the second drive signal is corrected according to a parameter corresponding to the volume of the sound source signal. Acoustic control device.

2. The different physical characteristics of the first speaker and the second speaker are at least one of the following: shape, weight, and material properties. The acoustic control device according to claim 1.

3. The aforementioned controller, The gain of the second drive signal is further corrected according to the aforementioned parameters. The acoustic control device according to claim 1.

4. The aforementioned controller, The phase of the second drive signal is corrected according to a parameter associated with the volume set by the user for the sound output from the first speaker. The acoustic control device according to claim 1.

5. The aforementioned controller, The parameters obtained are a value associated with the volume, indicating that the filter type is an all-pass filter, a value indicating the center frequency, and a Q value. The phase of the second drive signal is corrected by performing equalization using an all-pass filter according to the aforementioned parameters. The acoustic control device according to claim 1.

6. The controller Based on the sound source signal, a first drive signal is generated to drive a first speaker, and a second drive signal is generated to drive a second speaker which is provided so that its rear surfaces face the first speaker and which has different physical characteristics from the first speaker. The phase of the second drive signal is corrected according to a parameter associated with the volume of the sound source signal. The first speaker is driven based on the first drive signal, and the second speaker is driven based on the corrected second drive signal. Acoustic control method.

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