Acoustic device, acoustic control method, and acoustic control program

Abstract

To perform an appropriate surround reproduction which is appropriate to a sound source signal.SOLUTION: An acoustic device of the embodiment includes a control part. The control part calculates a difference of a first sound source signal and a second sound source signal, separated from the sound source signal as a sound component. The control part compresses the sound component on the basis of a smaller level of each level of the first sound source signal and the second sound source signal. The controls synthesizes the surround component after the compression and a direct sound based on the sound source signal.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to an acoustic device 、 and an acoustic control method , and sound control program . 【Background Art】 【0002】 Conventionally, for example, an acoustic device that outputs a sound source signal of various sound sources such as music and voice from a plurality of channels is known (see, for example, Patent Document 1). In the prior art, a pseudo reverberation sound generated from the sound source signal is positively added directly to the sound, and surround playback is performed with a plurality of channels. 【0003】 Also, for example, a technique is known that increases or decreases the surround effect according to the signal level of either the left audio signal or the right audio signal to prevent signal clipping (see, for example, Patent Document 2). 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent No. 5372142 【Patent Document 2】 Japanese Unexamined Patent Application Publication No. 2005-354444 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 However, there is room for improvement in the prior art in terms of performing appropriate surround playback according to the sound source signal. 【0006】 The present invention has been made in view of the above, and an object thereof is to provide an acoustic device and an acoustic control method capable of performing appropriate surround playback according to a sound source signal. 【Means for Solving the Problems】 【0007】 To solve the above problems and achieve the objective, the sound device of the present invention has a control unit. The control unit calculates the difference between a first sound source signal and a second sound source signal separated from the sound source signal as a surround component. The control unit compresses the surround component based on the smaller of the levels of the first sound source signal and the second sound source signal. The control unit synthesizes the compressed surround component with the direct sound based on the sound source signal and outputs it. [Effects of the Invention] 【0008】 According to the present invention, appropriate surround sound reproduction can be performed according to the sound source signal. [Brief explanation of the drawing] 【0009】 [Figure 1] Figure 1 is a diagram illustrating an overview of the acoustic control method according to the first embodiment. [Figure 2] Figure 2 is a block diagram showing an example configuration of an acoustic system equipped with an acoustic device according to the first embodiment. [Figure 3] Figure 3 illustrates the output methods for direct sound and surround sound. [Figure 4] Figure 4 is a flowchart showing the processing procedure performed by the acoustic device according to the first embodiment. [Figure 5] Figure 5 illustrates conventional direct sound and surround sound output methods. [Modes for carrying out the invention] 【0010】 The embodiments of the acoustic 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. 【0011】 (First Embodiment) <Outline of the acoustic control method using the acoustic device according to the first embodiment> Below, we will first describe the overview of the acoustic control method using the acoustic device according to the first embodiment with reference to Figure 1. Figure 1 is a diagram illustrating the overview of the acoustic control method according to the first embodiment. 【0012】 The sound control method according to the first embodiment is performed, for example, by the sound device 10 shown in Figure 1. In Figure 1, for example, in the interior space of a vehicle such as the passenger compartment, direct sound is output from speakers FR and FL positioned on the left and right sides at the front. In addition, simulated reverberation (hereinafter referred to as surround sound) is output from speakers RL and RR positioned on the left and right sides at the rear. At this time, surround sound is added to the direct sound to realize surround sound playback. Speakers FR, FL, RL, and RR may be provided in the sound device 10, or they may be provided as separate devices from the sound device 10. 【0013】 Here, the sound source signal is a signal from a sound source that has spatial breadth (sound image width) by outputting different sounds from, for example, two speakers FR and FL. In other words, the sound source signal is a stereo signal that is reproduced in stereo on two channels (speakers FR and FL). 【0014】 Furthermore, while a sound source signal is a sound that contains a mixture of multiple instrument sounds and vocals, such as classical music or opera, it is not limited to this. In other words, a sound source signal may be a sound signal containing only vocals, or a sound signal containing the sound of a single instrument (sound source), such as only a piano or only a violin. 【0015】 In the above, it was stated that direct sound etc. is output from speakers FR and FL, and surround sound is output from speakers RL and RR, but this is not limited to this. That is, for example, the sound device 10 may output direct sound etc. from all or some of the four speakers FR, FL, RL, and RR, and adjust the volume etc. 【0016】 Similarly, the audio device 10 may output surround sound from all or some of the four speakers FR, FL, RL, and RR and adjust its volume and other parameters. 【0017】 Conventionally, a method of generating surround sound from a sound source signal and adding the generated surround sound directly to the sound to realize surround sound reproduction is known. FIG. 5 is a diagram for explaining a conventional method of outputting direct sound and surround sound. 【0018】 As shown in FIG. 5, a conventional audio device receives the input of the time-series signal sL(t) of the sound source L and the time-series signal sR(t) of the sound source R. 【0019】 A conventional audio device adjusts the gain of the difference (sL(t) - sR(t)) between sL(t) and sR(t), and then applies a surround filter (for example, a FIR (Finite Impulse Response) filter or an IIR (Infinite Impulse Response) filter). Then, the obtained surround sound is output to a surround output speaker. 【0020】 Here, depending on the sound source, the difference between L and R may be extremely large. For example, there may be a case where there is a sound source only in the L channel and a case where the level of the sound source in the L channel is extremely higher than that in the R channel. In that case, a conventional audio device has a problem that the output surround sound becomes excessively large. 【0021】 In contrast, in the embodiment, the above problem is solved by appropriately adjusting the generated surround sound according to the difference between L and R of the sound source. 【0022】 <Configuration of an audio system including an audio device according to the first embodiment> Next, the configuration of the sound system equipped with the sound device 10 according to the first embodiment will be described with reference to Figure 2. Figure 2 is a block diagram showing an example configuration of the sound system equipped with the sound device 10 according to the first embodiment. In Figure 2, only the components necessary to explain the features of this embodiment are represented as functional blocks, and descriptions of general components are omitted. 【0023】 In other words, each component shown in Figure 2 is a functional concept and does not necessarily need to be physically configured as shown. For example, the specific forms of distribution and integration of each functional block are not limited to those shown, and it is possible to configure all or part of them by functionally or physically distributing and integrating them in any unit according to various loads and usage conditions. 【0024】 As shown in Figure 2, the sound system 1 comprises an acoustic device 10, a sound source device 20, and a plurality of speakers FL, FR, RL, and RR. While the sound system 1 according to this embodiment is mounted in a vehicle, it is not limited to this configuration. 【0025】 The sound source device 20 outputs a sound source signal to the sound device 10. The sound source signal is, for example, a stereo signal. The sound source signal is output through the sound device 10 as two different signals from two speakers, FL and FR, which are two channels, resulting in a sound image with spatial breadth. 【0026】 Multiple speakers FL, FR, RL, and RR are connected to the sound device 10. These speakers FL, FR, RL, and RR output the signal output from the sound device 10 as sound. For example, speakers FL and FR output the direct sound, which is the sound source signal, and speakers RL and RR output surround sound generated from the sound source signal, but this is not limited to this. 【0027】 The sound device 10 comprises a control unit 11 and a storage unit 12. The control unit 11 comprises an acquisition unit 111, a separation unit 112, and an output control unit 113. The sound device 10 includes, for example, a computer and various circuits having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), flash memory, input / output ports, etc. 【0028】 The computer's CPU functions as the acquisition unit 111, separation unit 112, and output control unit 113 of the control unit 11, for example, by reading and executing a program stored in ROM. 【0029】 Furthermore, at least one or all of the acquisition unit 111, separation unit 112, and output control unit 113 of the control unit 11 can be configured using hardware such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array). 【0030】 Furthermore, the storage unit 12 supports RAM and flash memory. RAM and flash memory can store information about various programs, etc. The sound device 10 may also acquire the above-mentioned programs and various information via other computers or portable recording media connected by wired or wireless networks. 【0031】 The acquisition unit 111 acquires various information and signals. For example, the acquisition unit 111 acquires a sound source signal from the sound source device 20. For example, the acquisition unit 111 acquires a sound source signal that is a stereo signal. Specifically, the acquisition unit 111 acquires the sound source signals output from each of the two speakers FL and FR, which are two channels. The acquisition unit 111 outputs the acquired sound source signals to the separation unit 112 and the output control unit 113. 【0032】 In the following, the audio source signal, which is a stereo signal, may be referred to as the "Lch audio source signal" if it is output (played) from speaker FL, which is the left channel, and as the "Rch audio source signal" if it is output from speaker FR, which is the right channel. 【0033】 The separation unit 112 separates and extracts the L component sound source signal and the R component sound source signal from the sound source signal. The separation unit 112 may separate and extract the L channel sound source signal and the R channel sound source signal of the sound source signal as they are, or it may separate and extract each component by processing such as masking in the time domain and frequency domain. 【0034】 The L component sound source signal is a sound source signal that contains the sound component (L component) reproduced by one of the two channels, speaker FL and FR (speaker FL). The R component sound source signal is a sound source signal that contains the sound component (R component) reproduced by the other channel (speaker FR). Note that the L component sound source signal is an example of a first sound source signal, and the R component sound source signal is an example of a second sound source signal. 【0035】 The separation unit 112 outputs the separated and extracted L component sound source signal and R component sound source signal to the output control unit 113. 【0036】 The output control unit 113 processes the L component sound source signal and the R component sound source signal and outputs them from speakers FL, FR, RL, and RR. 【0037】 The processing of the output control unit 113 will be explained using Figure 3. Figure 3 is a diagram illustrating the output method for direct sound and surround sound. 【0038】 As shown in Figure 3, first, the output control unit 113 receives inputs of an L component sound source signal sL(t) and an R component sound source signal sR(t). The L component sound source signal sL(t) is an example of a first sound source signal. The R component sound source signal sR(t) is an example of a second sound source signal. 【0039】 The output control unit 113 outputs the L component sound source signal sL(t) and the R component sound source signal sR(t) directly to the sound output speakers (e.g., FR, FL). 【0040】 Thus, a speaker for direct sound output outputs direct sound based on the sound source signal. A speaker for direct sound output is an example of the first speaker. 【0041】 Meanwhile, the output control unit 113 calculates the difference sL(t)-sR(t) between the L component sound source signal sL(t) and the R component sound source signal sR(t) as the surround component (step S101). 【0042】 Furthermore, the output control unit 113 performs smoothing by calculating the average of the absolute values ​​of the L component sound source signal sL(T) and R component sound source signal sR(T) for T frames, respectively (step S102). For example, T=8 (where fs=48kHz). 【0043】 In this way, the output control unit 113 calculates the absolute value of the average level of the first sound source signal over a certain period (e.g., T) as the first value, and calculates the absolute value of the average level of the second sound source signal at each time point during that period as the second value. This allows the sound source signal to be smoothed. 【0044】 Next, the output control unit 113 calculates a compression coefficient for compressing the surround component (step S103). Here, the compression coefficient w(T) is assumed to be equal to the smaller of |sL(T)| and |sR(T)|. 【0045】 A small compression factor means that the surround components to which that compression factor is applied become smaller (more strongly compressed). 【0046】 Next, the output control unit 113 adjusts the gain of the compression coefficient w(T) and then applies an LPF (Low Pass Filter) to further smooth the signal (step S104). 【0047】 For example, in step S104, the output control unit 113 uses an FIR or IIR with an order of magnitude of 2 and a passband edge frequency of 1 Hz. 【0048】 In this way, the output control unit 113 calculates a compression coefficient based on the smaller of the levels of the first sound source signal and the second sound source signal, further smooths it using an LPF, and compresses the surround components using this smoothed compression coefficient. As a result, the compression coefficient is further smoothed, and the surround components can be compressed appropriately. 【0049】 Furthermore, the output control unit 113 limits the compression coefficient w(T) by a predetermined limiter (step S105). For example, the output control unit 113 implements the limiter by multiplying the compression coefficient w(T) by a predetermined value in the range of 0 to 1 (e.g., 0.8). 【0050】 Subsequently, the output control unit 113 multiplies the difference sL(t)-sR(t) calculated in step S101 by the compression coefficient w(T) (step S106). 【0051】 In this way, the output control unit 113 compresses the surround components based on the smaller of two values: a first value obtained by smoothing the level of the first sound source signal and a second value obtained by smoothing the level of the second sound source signal. |sL(T)| and |sR(T)| are examples of the first and second values, respectively. 【0052】 In this way, by compressing the surround components using a compression coefficient based on the smaller of the L component sound source signal and the R component sound source signal, the surround sound becoming excessively loud is suppressed. 【0053】 Furthermore, the output control unit 113 limits the surround component with a limiter (step S107) and combines the L component sound source signal sL(t) and the R component sound source signal sR(t) (step S108). 【0054】 Then, the output control unit 113 applies a surround filter (e.g., an FIR filter or IIR filter) to the synthesized surround component (step S109) and outputs it to the surround output speakers (e.g., RR, RL). 【0055】 Thus, surround output speakers output sound obtained by combining the compressed surround component with the direct sound based on the sound source signal. The surround output speaker is an example of the first speaker. 【0056】 The method, timing, and number of smoothing operations are not limited to those described herein. The output control unit 113 performs smoothing at least once at one of the timings. 【0057】 Furthermore, the method, timing, and number of times the limiter is applied are not limited to those described here. The output control unit 113 does not need to implement a limiter. 【0058】 Furthermore, the output control unit 113 can perform processing such as D / A conversion and amplification of the audio signal as appropriate. 【0059】 Figure 4 is a flowchart showing the processing procedure performed by the acoustic device according to the first embodiment. As shown in Figure 4, the acoustic device 10 acquires a sound source signal (step S11). For example, the acoustic device 10 acquires an acoustic signal from the sound source device 20. 【0060】 Next, the sound device 10 separates the L component sound source signal and the R component sound source signal from the sound source signal (step S12). 【0061】 Next, the sound device 10 calculates the surround component from the difference between the L component sound source signal and the R component sound source signal (step S13). 【0062】 Here, the signal with the lower level between the L component sound source signal and the R component sound source signal is smoothed (step S14). Based on the smoothed value, the sound device 10 can calculate a compression coefficient to be multiplied by the surround component. 【0063】 The sound device 10 compresses the surround components based on the smoothed values ​​(step S15). Then, the sound device 10 outputs the direct sound components and the surround components after the compression (step S16). 【0064】 As described above, the sound device 10 according to the first embodiment has a control unit 11. The control unit 11 calculates the difference between the first sound source signal and the second sound source signal separated from the sound source signal as the surround component. The control unit 11 compresses the surround component based on the smaller of the levels of the first sound source signal and the second sound source signal. The control unit 11 synthesizes the compressed surround component with the direct sound based on the sound source signal and outputs it. This enables appropriate surround sound reproduction according to the sound source signal. 【0065】 Here, we will explain the effects of different levels of the L component and R component sound source signals. The levels are represented in three categories: large, medium, and small, and the compression ratio is proportional to the smaller level. 【0066】 When the level of the left (L) component sound source signal is high and the level of the right (R) component sound source signal is low, the difference between the levels of the L and R components is large, resulting in the surround component level being too high. On the other hand, the compression ratio in this case is proportional to the low level, so the surround component after compression is kept low. 【0067】 When the level of the left (L) component sound source signal is medium and the level of the right (R) component sound source signal is high, the difference between the levels of the L and R components is medium, so the level of the surround component will be at an appropriate size. Also, the compression ratio at this time is proportional to the medium level, so the compressed surround component will still be at an appropriate size. 【0068】 When the level of the left (L) component sound source signal is medium and the level of the right (R) component sound source signal is medium, the difference between the levels of the L component signal and the R component signal is small, so the level of the surround component will be small. Also, the compression ratio in this case will be proportional to the medium level, so the surround component after compression will not become too large. 【0069】 When the level of the left (L) component sound source signal is medium and the level of the right (R) component sound source signal is low, the difference between the levels of the L and R components is moderate, resulting in an appropriate level for the surround components. Furthermore, the compression ratio in this case is proportional to the low level, so the resulting surround components will not become excessively large. 【0070】 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] 【0071】 1. Sound System 10 Sound equipment 11 Control Unit 12 Storage section 20 Sound source device 111 Acquisition Department 112 Separation section 113 Output Control Unit

Claims

[Claim 1] The difference between the first sound source signal and the second sound source signal, separated from the original sound source signal, is calculated as the surround component. A first smoothed value is calculated by smoothing the level of the first sound source signal. A second smoothed value is calculated by smoothing the level of the second sound source signal. Based on the smaller of the first smoothing value and the second smoothing value, a compression coefficient is calculated such that a smaller smoothing value results in stronger compression. The surround component is compressed based on the compression coefficient. The system includes a control unit that synthesizes the compressed surround sound component with the direct sound based on the sound source signal and outputs the result. sound equipment. [Claim 2] The control unit, The absolute value of the average level of the first sound source signal over a certain period is calculated as the first smoothed value, and the absolute value of the average level of the second sound source signal at each time point during the period is calculated as the second smoothed value. The acoustic device according to claim 1. [Claim 3] The control unit, The compression coefficient calculated based on the smaller of the levels of the first sound source signal and the second sound source signal is further smoothed using an LPF, and the surround component is compressed using the smoothed compression coefficient. The acoustic device according to claim 1. [Claim 4] A first speaker that outputs direct sound based on the sound source signal, A second speaker that outputs sound obtained by synthesizing the surround component after the compression and the direct sound based on the sound source signal, The sound device according to claim 1, further comprising the features. [Claim 5] The control unit of the sound device, The difference between the first sound source signal and the second sound source signal, separated from the original sound source signal, is calculated as the surround component. A first smoothed value is calculated by smoothing the level of the first sound source signal. A second smoothed value is calculated by smoothing the level of the second sound source signal. Based on the smaller of the first smoothing value and the second smoothing value, a compression coefficient is calculated such that a smaller smoothing value results in stronger compression. The surround component is compressed based on the compression coefficient. The surround sound component after compression and the direct sound based on the sound source signal are combined and output. Acoustic control method. [Claim 6] The control unit of the sound device, The difference between the first sound source signal and the second sound source signal, separated from the original sound source signal, is calculated as the surround component. A first smoothed value is calculated by smoothing the level of the first sound source signal. A second smoothed value is calculated by smoothing the level of the second sound source signal. Based on the smaller of the first smoothing value and the second smoothing value, a compression coefficient is calculated such that a smaller smoothing value results in stronger compression. The surround component is compressed based on the compression coefficient. The surround sound component after compression and the direct sound based on the sound source signal are combined and output. An acoustic control program that executes processing.

Images