JP2024056433A - Acoustic control device - Google Patents

Abstract

To accurately cancel vibrations with a simple configuration in an asymmetric R2R speaker.SOLUTION: In an audio amplifier of an embodiment, based on a sound source signal, there are generated: a first drive signal to drive a first speaker; a second drive signal to drive a second speaker that is provided such that the back surface of the first speaker faces that of the second speaker and that has a physical property different from that of the first speaker, the phase of the second drive signal being an opposite phase of the first drive signal; and a third drive signal to drive a third speaker that is different from both the first speaker and the second speaker. In the audio amplifier, the first drive signal is transmitted to one channel associated with the first speaker, and a superimposed signal obtained by superimposing the second drive signal and the third drive signal is transmitted to one channel associated with both the second speaker and the third speaker.SELECTED DRAWING: Figure 3

Description

The present invention relates to an acoustic control device.

Speakers are designed to generate sound by creating air vibrations caused by a diaphragm moving back and forth. When this happens, the reaction to the movement causes the ceramic circuit and frame to move to some extent, which creates unwanted vibrations (distortion) compared to the accurate vibration of the diaphragm. Furthermore, these unwanted vibrations can be transmitted to surrounding components fixed to the speaker, causing abnormal noise.

In response to this, a technology is known that uses a weight attached to the back side of the magnetic circuit to suppress vibration of the magnetic circuit (see, for example, Patent Document 1).

Furthermore, the R2R (Rear to Rear) system is known, in which opposing speakers of the same shape are driven with an in-phase signal to cancel out vibrations (see, for example, Non-Patent Document 1). Each speaker that makes up the R2R system is sometimes called a unit. Two speakers that are configured using the R2R system are sometimes called an R2R speaker.

The R2R system allows the drive vibrations of the units and air pressure fluctuations to cancel each other out, preventing abnormal noise from coming from the housing.

The R2R method is also known by other names such as "rear-to-rear facing structure," "dual opposed," and "force cancelling." The R2R method is also sometimes used in home speaker systems.

JP 2002-152884 A

DENSO TEN, "TD316SWMK2", [online], [Retrieved July 11, 2022], Internet (https://www.eclipse-td.com/products/td316swmk2/index.html)

To make R2R speakers smaller, it is possible to give the speakers different shapes. In this case, the two speakers are called asymmetric R2R speakers.

However, in asymmetric R2R speakers, because the physical characteristics of the speakers are different from each other, in order to cancel vibrations with precision, it is necessary to provide a function for generating drive signals and a dedicated channel for each of the two speakers.

In order to solve the above-mentioned problems and achieve the object, the acoustic control device according to the present invention generates, based on a sound source signal, a first drive signal for driving a first speaker, a second drive signal for driving a second speaker that is arranged so that its back faces the first speaker and has physical characteristics different from those of the first speaker, and that is an inverse phase of the first drive signal, and a third drive signal for driving a third speaker that is different from both the first speaker and the second speaker. The acoustic control device transmits the first drive signal to one channel associated with the first speaker, and transmits a superimposed signal in which the second drive signal and the third drive signal are superimposed to one channel associated with both the second speaker and the third speaker.

According to the present invention, vibrations can be canceled accurately in an asymmetric R2R speaker with a simple configuration.

FIG. 1 is a diagram showing an example of speaker arrangement. FIG. 2 is a diagram showing an example of the configuration of an asymmetric R2R speaker. FIG. 3 is a diagram showing an example of the configuration of an audio system. FIG. 4 is a diagram showing the phase difference between the ringing side and the canceling side. FIG. 5 is a diagram showing an example of sound pressure for each frequency band of an audio signal after equalization. FIG. 6 is a diagram showing an example of sound pressure for each frequency band of the drive signal transmitted from the P-IC. FIG. 7 is a flowchart showing the flow of processing in the acoustic signal processing unit. FIG. 8 is a diagram showing the configuration of a conventional R2R speaker.

First, a conventional R2R speaker will be described using Figure 8. Figure 8 is a diagram showing the configuration of a conventional R2R speaker.

As shown in FIG. 8, R2R speaker 40a is made up of speaker 41a and speaker 42a joined back-to-back. "Back-to-back" means that the components opposite the diaphragm that produces sound are joined together.

Conventional R2R speakers have the problem that the overall size of the device is large. In addition, conventional R2R speakers require the two speakers to have the same shape, which reduces design freedom.

In this embodiment, an asymmetric R2R speaker is used to solve the problems with conventional R2R speakers.

Asymmetric R2R speakers allow the physical characteristics of the two speakers to be different from each other. For example, in an asymmetric R2R speaker, one of the speakers is smaller than a conventional R2R speaker.

On the other hand, in asymmetric R2R speakers, the physical characteristics of the two speakers are different, so simply inputting the same drive signal to the two speakers may not be enough to cancel out the vibrations.

This is because the two speakers have different shapes, weights, material properties, etc. Shape, weight, material properties, etc. are examples of physical properties. For example, the different physical property between speaker 41a and speaker 42a is at least one of the shapes, weights, and material properties.

As mentioned above, in an asymmetric R2R speaker, one speaker is made smaller than the other. For example, when making the speakers smaller, the structures and materials of the two speakers may differ from each other, which may result in the two speakers having different physical characteristics.

For example, if the same drive signal is input to two speakers of different weights, differences will arise in the vibration period and amplitude of the two speakers, and these differences may cause unwanted vibrations and abnormal noise.

In this embodiment, one objective is to accurately cancel vibrations in an asymmetric R2R speaker using a simple configuration.

The following describes in detail an embodiment of the acoustic control device disclosed in the present application with reference to the attached drawings. Note that the present invention is not limited to the embodiment described below.

In this embodiment, the asymmetric R2R speaker is mounted on a vehicle. However, the asymmetric R2R speaker of the embodiment may be installed on a moving object other than a vehicle, or inside or outside a building.

Figure 1 is a diagram showing an example of speaker placement. As shown in Figure 1, vehicle 1 is equipped with speaker 31, speaker 32, speaker 33, speaker 34, speaker 35, speaker 36, speaker 37, and speaker 40.

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

The speaker 40 is provided in the center of the rear seat. The speaker 40 is an asymmetric R2R speaker. The speaker 40 may be a speaker that functions as a woofer that outputs low-frequency sound. Note that the position where the speaker 40 is placed is not limited to the center of the rear seat, and may be any position in the vehicle 1.

Here, one side of the asymmetric speaker is called the ringing side. The side of the asymmetric speaker opposite the ringing side is called the cancellation side. Speaker 40 corresponds to two channels: Woofer 1 on the ringing side and Woofer 2 on the cancellation side.

However, in this embodiment, the channel for Woofer2 is assumed to be shared with channels for other speakers other than speaker 40. The configuration for the channel for Woofer2 will be described later.

The vehicle 1 is also equipped with a playback device 10 and an audio amplifier 20. The playback device 10 inputs a sound playback signal to the audio amplifier 20. The audio amplifier 20 transmits a signal for outputting sound to each speaker based on the playback signal. Note that the playback device 10 and the audio amplifier 20 may be separate devices or may be integrated.

The signal output by the audio amplifier 20 is called a drive signal because it is a signal for driving a speaker.

The playback device 10 may be any device that functions as a sound source, such as a car navigation system, a drive recorder, a car audio system, or a smartphone.

The audio amplifier 20 performs processes such as filtering, mixing, noise removal, and amplification using FIR (Finite Impulse Response) and IIR (Infinite Impulse Response) on the playback signal.

Furthermore, the audio amplifier 20 transmits a drive signal to the speaker 40, which is an asymmetric R2R speaker, that can cancel vibrations with high precision. The drive signal transmitted to the speaker 40 will be described in detail later.

The audio amplifier 20 is an example of an acoustic control device and executes an acoustic control method.

Here, the configuration of the speaker 40 will be explained using Figure 2. Figure 2 is a diagram showing an example of the configuration of an asymmetric R2R speaker.

As shown in FIG. 2, the speaker 40 has a ringing speaker 41 and a cancellation speaker 42. In addition, a part of the ringing speaker 41 and the cancellation speaker 42 are housed in a housing 45. In addition, as shown in FIG. 2, the back surface of the ringing speaker 41 faces the back surface of the cancellation speaker 42.

The ringing speaker 41 includes a voice coil 411, a magnetic circuit 412, a diaphragm 413, and a connecting portion 414. The cancellation speaker 42 includes a voice coil 421, a magnetic circuit 422, and a connecting portion 424.

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

Even if the cancellation side speaker 42 does not have a diaphragm, it generates vibrations in response to a drive signal. The cancellation side speaker 42 cancels the vibrations of the sounding side speaker 41 through this vibration.

In addition, the coupling parts 414 and 424 are made of metal, resin, or other materials, and vibrate together with the voice coils 411 and 421, respectively.

The connecting parts 414 and 424 do not need to be in close contact as in FIG. 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. The connecting parts 414 and 424 may also be pistons arranged opposite each other in a cylinder. In this case, the vibration is canceled by the air pressure in the space between the pistons.

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

As shown in FIG. 3, the playback device 10 inputs playback signals of multiple channels to the audio amplifier 20. The audio amplifier 20 outputs driving vibrations of multiple channels.

The playback device 10 inputs a main audio signal and a sub-audio signal to the audio amplifier 20 as playback signals. The main audio signal is, for example, a music signal (music sound source and movie sound source). The sub-audio signal is, for example, a navigation voice, an operation beep, voice recognition guidance, ANC (Active Noise Canceling), etc.

The audio amplifier 20 has an audio signal processing section 21 and a P-IC (power amplifier IC) 22. The audio signal processing section 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.

For example, the acoustic signal processing unit 21 is realized by a computer's CPU functioning as a controller and reading and executing a program stored in a ROM (Read Only Memory). The acoustic signal processing unit 21 is an example of a controller that generates a speaker drive signal based on a sound source signal. The speaker drive signal is a drive signal that the acoustic signal processing unit 21 outputs to each speaker. The controller may also realize both the acoustic signal processing unit 21 and the P-IC 22, rather than realizing only the acoustic signal processing unit 21.

The controller may also be a microcontroller, a DSP (Digital Signal Processor), an ECU (Electronic Control Unit), an FPGA (Field Programmable Gate Array), a GPU (Graphics Processing Unit), a SoC (System on a Chip), etc.

The controller may be a single processor or a multi-processor configuration. The controller may also be a multi-core configuration with multiple cores in a single chip connected to a single socket.

The audio signal processing unit 21 has a main audio distribution unit 211, an EQ (equalizer) 2121, an EQ2122, an EQ2123, an EQ2124, an EQ2125, an EQ2126, an EQ2127, a sub audio mixing unit 213, a filter 2141, and a filter 2142.

The main audio distribution unit 211 distributes the main audio signal received from the playback device 10 to each EQ.

Each EQ performs equalization according to the corresponding speaker. However, EQ2127 performs equalization corresponding to both the ringing speaker 41 and the cancellation speaker 42.

The sub-audio mixing unit 213 mixes the sub-audio into the equalized audio signal intended for each speaker.

The filter 2141 filters the audio signal that has been equalized by the EQ 2127 and mixed with the sub audio signal, and generates a ringing side drive signal to be transmitted to the ringing side speaker 41 (Woofer1 (ringing side)).

Furthermore, filter 2142 filters the audio signal that has been equalized by EQ 2127 and mixed with the sub audio signal, and generates a cancellation side drive signal to be transmitted to cancellation side speaker 42 (Woofer2 (cancellation side)).

In this way, filters 2141 and 2142 are provided after the sub-audio mixing unit 213 (on the speaker side), and generate a ringing drive signal, a cancellation drive signal, and drive signals for other speakers including speaker 37 based on a sound source signal that is a mixture of a main playback signal that plays music and a sub playback signal that plays sounds other than music. This makes it possible to cancel vibrations regardless of the various types of sounds represented by the main audio signal and the sub-audio signal.

Here, as shown in Figure 4, when the same drive signal is input to both the ringing speaker 41 and the cancellation speaker 42, the vibration phase of each speaker differs in a specific band. Figure 4 shows the difference in phase between the ringing side and the cancellation side.

The phase difference also differs depending on the band. This is because the physical characteristics of the ringing speaker 41 and the cancellation speaker 42 are different from each other.

Figure 4 shows the phase of the vibration generated by each speaker when a drive signal corresponding to a volume of 1 W is input.

In the example of FIG. 4, the phases of the ringing speaker 41 and the cancellation speaker 42 are roughly the same in the band of approximately 60 Hz and above. In contrast, in the band of 25 Hz to 60 Hz, the phase of the cancellation speaker 42 exceeds the phase of the ringing speaker 41. On the other hand, in the band of 25 Hz and below, the phase of the cancellation speaker 42 is below the phase of the ringing speaker 41.

Filters 2141 and 2142 perform filtering to eliminate the phase difference in each band between the ringing speaker 41 and the cancellation speaker 42. In addition, filtering by filters 2141 and 2142 may cause the sound pressure of the drive signal to change.

The filtering by filters 2141 and 2142 may be a process similar to equalization. Furthermore, audio amplifier 20 may be configured to include either filter 2141 or filter 2142.

Based on the input playback signal, the acoustic signal processing unit 21 generates a ringing side drive signal that drives the ringing side speaker 41, a cancellation side drive signal that drives the cancellation side speaker 42, which is arranged with its back facing the ringing side speaker 41 and has physical characteristics different from those of the ringing side speaker 41, and is in the opposite phase to the ringing side drive signal, and a center drive signal that drives a speaker 37 that is different from both the ringing side speaker 41 and the cancellation side speaker 42.

The playback signal is an example of a sound source signal. The ringing speaker 41 is an example of a first speaker. The cancellation speaker 42 is an example of a second speaker. The speaker 37 is an example of a third speaker. The ringing drive signal is an example of a first drive signal. The cancellation drive signal is an example of a second drive signal. The Center drive signal is an example of a third drive signal.

Furthermore, the audio signal processing unit 21 mixes the cancellation side audio signal output from the filter 2142 with the center drive signal that has been equalized by the EQ 2126 and mixed with the sub audio signal. For example, the audio signal processing unit 21 superimposes the cancellation side drive signal on the center drive signal.

As shown in Fig. 5, the frequency bands of the Center audio signal (Center in Fig. 5) that has been equalized by EQ2126 and the Woofer audio signal (Woofer in Fig. 5) that has been equalized by EQ2127 tend not to overlap. Fig. 5 shows an example of sound pressure for each frequency band of the audio signal after equalization.

Furthermore, as shown in Figure 6, a similar trend to Figure 5 is seen in the stage subsequent to the P-IC 22. Figure 6 shows an example of sound pressure for each frequency band of the drive signal transmitted from the P-IC.

The acoustic signal processing unit 21 transmits the ringing side drive signal to one channel associated with the ringing side speaker 41 via the P-IC 22, and transmits a superimposed signal, which is the cancellation side drive signal superimposed with the center drive signal, to one channel associated with both the cancellation side speaker 42 and the speaker 37.

In this way, because the channels of the cancellation side speaker 42 and the speaker 37 are integrated into one, when adding two speakers, the ringing side speaker 41 and the cancellation side speaker 42, only one channel needs to be added. As a result, in an asymmetric R2R speaker, vibrations can be canceled with high precision using a simple configuration.

As shown in Figure 6, in a drive signal in which the cancellation side drive signal is superimposed on the Center drive signal (Center + Woofer 2 (cancellation side)), the frequency bands of the drive signals are clearly separated.

For this reason, when the center drive signal and the cancellation drive signal are superimposed, each drive signal can be easily separated using a passive filter, etc.

Here, speaker 37, located in the center of FIG. 1, has a smaller aperture than speaker 40 and outputs sounds mainly in the high frequency band (e.g., 200 Hz or higher). On the other hand, speaker 40 functions as a woofer and outputs sounds mainly in the low frequency band (e.g., 100 Hz or lower).

In addition, the channel on which the acoustic signal processing unit 21 superimposes the cancellation side drive signal is not limited to the Center, and may be another channel. The channel on which the acoustic signal processing unit 21 superimposes the cancellation side drive signal is a channel shared by the Center and Woofer 2.

Furthermore, as shown in FIG. 3, the drive signal in which the cancellation side drive signal is superimposed on the center drive signal (hereinafter, the superimposed signal) is filtered by the capacitor 51 and then output to the speaker 37 (center).

The superimposed signal is also filtered by coil 61 and then output to the cancellation side speaker 42.

The superimposed signal is also filtered by coil 62 and then output to the sound-generating speaker 41.

Capacitor 51 functions as a high-pass filter, passing the center drive signal from the superimposed signal but not the cancellation drive signal. As a result, the center drive signal is input to speaker 37, but the cancellation drive signal is not input. The center drive signal is an example of a high-frequency component of the superimposed signal. Capacitor 51 is also an example of a first passive filter.

The coil 61 functions as a low-pass filter, passing the cancellation side drive signal from the superimposed signal but not the center drive signal. As a result, the cancellation side drive signal is input to the cancellation side speaker 42, but the center drive signal is not input. The cancellation side drive signal is an example of a low-frequency component that is lower than the treble range of the superimposed signal. The coil 61 is also an example of a second passive filter.

Here, the characteristics of the cancellation side drive signal may change due to the influence of coil 61. Coil 62 serves to match the characteristics of the ringing side drive signal to changes in the characteristics of the cancellation side drive signal.

In this way, in this embodiment, the cancellation side drive signal can be separated from the superimposed signal using a simple configuration that uses a passive filter.

The capacitor 51, the coil 61, and the coil 62 may be included in the audio amplifier 20. The capacitor 51, the coil 61, and the coil 62 may be part of a system that includes the audio amplifier 20, the playback device 10, and each speaker.

The processing flow of the audio signal processing unit will be described using Figure 7. Figure 7 is a flowchart showing the processing flow of the audio signal processing unit.

As shown in FIG. 7, first, the audio signal processing unit 21 accepts input of the main and sub playback signals (step S101).

Next, the audio signal processing unit 21 distributes the main playback signal to the equalizer (step S102). The audio signal processing unit 21 then performs equalization on the distributed playback signal (step S103).

Then, the audio signal processing unit 21 mixes the equalized audio signal with the sub playback signal (step S104).

Then, the audio signal processing unit 21 generates drive signals for each channel, including a ringing drive signal, a cancellation drive signal, and a Center drive signal, from the mixed audio signal (step S105).

The audio signal processing unit 21 transmits the ringing side drive signal to the channel of the ringing side speaker (step S106). Furthermore, the audio signal processing unit 21 superimposes the cancellation side drive signal on the center drive signal and transmits it to the channel of the center speaker (step S107).

The drive signal sent to the Center speaker channel is input to each speaker via a passive filter.

As described above, the audio amplifier 20 according to the embodiment generates, based on a sound source signal, a first drive signal for driving a first speaker, a second drive signal for driving a second speaker that is arranged so that its back faces the first speaker and has physical characteristics different from those of the first speaker, and that is in the opposite phase to the first drive signal, and a third drive signal for driving a third speaker that is different from both the first speaker and the second speaker. The audio amplifier 20 transmits the first drive signal to one channel associated with the first speaker, and transmits a superimposed signal in which the second drive signal and the third drive signal are superimposed to one channel associated with both the second speaker and the third speaker.

This allows the audio amplifier 20 to accurately cancel vibrations in an asymmetric R2R speaker with a simple configuration.

In addition, as shown in Figures 1 and 3, by using an 8-channel audio amplifier, no additional components are required, so the configuration of the embodiment can be realized without increasing cost and size (including weight).

In addition, this embodiment makes it possible to change the shape, reduce the size, and reduce the weight of the cancellation side speaker 42, thereby increasing the freedom of design for asymmetric R2R speakers.

Further advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

REFERENCE SIGNS LIST 1 vehicle 10 playback device 20 audio amplifier 31, 32, 33, 34, 35, 36, 37, 40 speaker 41 sound generating speaker 42 cancellation speaker 45 housing 51 capacitor 61, 62 coil 211 main audio distribution section 213 sub audio mixing section 411, 421 voice coil 412, 422 magnetic circuit 413 diaphragm 414, 424 coupling section 2121, 2122, 2123, 2124, 2125, 2126, 2127 EQ
2141, 2142 Filter

Claims (4)

A controller is provided for generating a speaker driving signal based on a sound source signal,
The controller:
based on the sound source signal, generate a first drive signal for driving a first speaker, a second drive signal for driving a second speaker that is provided so as to face the back surface of the first speaker and has physical characteristics different from those of the first speaker, and that is an inverse phase of the first drive signal, and a third drive signal for driving a third speaker that is different from both the first speaker and the second speaker;
an acoustic control device that transmits the first drive signal to one channel associated with the first speaker, and transmits a superimposed signal obtained by superimposing the second drive signal and the third drive signal to one channel associated with both the second speaker and the third speaker. The acoustic control device according to claim 1 , wherein the different physical characteristics of the first speaker and the second speaker are at least one of shapes, weights, and material properties. The controller:
The acoustic control device according to claim 1 , wherein the first drive signal, the second drive signal, and the third drive signal are generated based on a sound source signal that is a mixture of a main playback signal that reproduces music and a sub playback signal that reproduces sounds other than music. a first passive filter that passes a high-frequency component of the superimposed signal and outputs the high-frequency component to the third speaker;
a second passive filter that passes a bass component of the superimposed signal that is lower than the treble component and outputs the bass component to the second speaker;
The acoustic control device according to claim 1 , further comprising:

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