JP7149216B2 - Acoustic device and acoustic control method - Google Patents

Description

The present invention relates to an acoustic device and an acoustic control method.

2. Description of the Related Art Conventionally, for example, in a space such as a passenger compartment of a vehicle, there has been known an acoustic device that outputs acoustic signals of various sound sources such as music and voice from a plurality of speakers arranged in the space. Also known is a technique of measuring acoustic characteristics in space of sound output from an acoustic device and adjusting an acoustic signal based on the measured acoustic characteristics (see, for example, Patent Document 1).

JP 2005-252467 A

By the way, in the measurement of the acoustic characteristics described above, the impulse response of the sound output from the acoustic device may be used. For example, in the impulse response, a predetermined time is set as a threshold, and the initial component including the direct sound and the early reflected sound before the predetermined time and the late component including the reverberant sound after the predetermined time are divided into the initial component and the late component. A ratio of the components may be calculated and measurements of acoustic properties may be made based on the ratio. However, the above-mentioned ratio becomes a value having a correlation with the acoustic characteristics, for example, in a relatively large space such as a listening room, where the direct sound, the early reflected sound, and the reverberant sound are separated at the boundary of a predetermined time. This is the case.

However, in a relatively narrow space such as a vehicle interior, the direct sound, the early reflected sound, and the reverberant sound are not separated at the boundary for a predetermined time, and the reverberant sound is mixed with the initial components including the direct sound and the early reflected sound. put away. Therefore, if the ratio calculated as described above is used, there is a possibility that the measurement accuracy of the acoustic characteristics is lowered.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an acoustic device and an acoustic control method capable of accurately measuring acoustic characteristics.

In order to solve the above problems and achieve the object, the present invention provides an acoustic device comprising a first calculator and a second calculator. A first calculator calculates, in an impulse response of a predetermined sound, the components of the predetermined sound by a threshold value obtained from the law of the first wavefront, the first component including the direct sound, and the sound delayed with respect to the direct sound. A predetermined value is calculated based on the second component. The second calculator calculates an index value indicating acoustic characteristics of the predetermined sound based on the predetermined value calculated by the first calculator.

According to the present invention, acoustic characteristics can be measured with high accuracy.

FIG. 1A is an explanatory diagram for explaining acoustic characteristics. FIG. 1B is a diagram showing a sound impulse response in a listening room. FIG. 1C is a diagram (part 1) showing the impulse response of sound in the vehicle compartment. FIG. 1D is a diagram (part 2) showing the impulse response of sound in the vehicle compartment. FIG. 1E is a diagram (part 3) showing the impulse response of sound in the vehicle compartment. FIG. 2 is a block diagram showing a configuration example of an acoustic system including acoustic devices. FIG. 3A is a diagram showing the correlation between the index value of the left-right width of the sound image and the component ratio. FIG. 3B is a diagram showing the correlation between the index value of the sound image front-back width and the component ratio. FIG. 3C is a diagram showing the correlation between the index value of the sound image distance and the component ratio. FIG. 3D is a diagram showing the correlation between the index value of the feeling of being wrapped and the component ratio. FIG. 3E is a diagram showing the correlation between the index value of sound image clarity and the component ratio. FIG. 3F is a diagram showing the correlation between the wrapped feeling index value and the separation component ratio. FIG. 4 is an explanatory diagram for explaining information about index values indicating acoustic characteristics. FIG. 5 is a flow chart showing a processing procedure executed by the audio device according to the first embodiment. FIG. 6A is a diagram showing impulse responses for each band in home audio. FIG. 6B is a diagram showing the amplitude of sound pressure in car audio. FIG. 6C is a diagram showing impulse responses by band in car audio. FIG. 6D is a schematic explanatory diagram of the acoustic control method according to the second embodiment. FIG. 7 is a block diagram showing a configuration example of an audio device according to the second embodiment. FIG. 8 is a schematic diagram showing acoustic effects obtained by the acoustic device. FIG. 9 is an explanatory diagram of high-frequency delay processing and low-frequency delay processing. FIG. 10 is a flow chart showing a processing procedure executed by the audio device according to the second embodiment.

Hereinafter, embodiments of the acoustic device and the acoustic control method disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

(First embodiment)
First, an overview of the sound control method by the sound device according to the first embodiment will be described below with reference to FIGS. 1A to 1E. FIG. 1A is an explanatory diagram for explaining acoustic characteristics. FIG. 1B is a diagram showing impulse responses of sounds in the listening room. Also, FIGS. 1C to 1E are diagrams showing impulse responses of sound in a vehicle compartment.

As shown in FIG. 1A, it is known that a listener L listening to sound from a sound source S in space can perceive multiple types of spatial impressions as acoustic characteristics. For example, as the acoustic characteristics, the sound image left-right width ASW1 and the sound image front-rear width ASW2, which are defined as "the width of the apparent sound source" that is perceived by merging with the direct sound both temporally and spatially, There is a sound image distance R defined as "the distance between the sound sources", and a sense of envelopment LEV defined as "a feeling that the surroundings of the listener are filled with sound sources other than the apparent sound source". In the following, when the sound image left-right width ASW1 and the sound image front-rear width ASW2 are not particularly distinguished, they are referred to as a sound image width ASW. Note that the listener L is an example of a listener.

Impulse response of sound can be used for measurement (evaluation) of acoustic characteristics such as sound image width ASW, sound image distance R, and enveloping feeling LEV. The impulse response includes direct sound, early reflected sound, and reverberant sound. For example, in a relatively large space such as a listening room, as shown in FIG. Reverberant sound is separated. In FIG. 1B, the direct sound is indicated by enclosing it in a two-dot chain line circle B. As shown in FIG.

Therefore, in measuring the acoustic characteristics, for example, in the impulse response, a predetermined time Ta is set as a threshold value (indicated by a one-dot chain line), and the initial component A1 including the direct sound and the early reflected sound before the predetermined time Ta and the predetermined A ratio of the early component A1 and the late component A2 is calculated by dividing it into the late component A2 including the reverberant sound after the time Ta. Then, the acoustic characteristics can be measured based on the calculated ratio and the correlation between the acoustic characteristics and the ratio obtained in advance.

However, as shown in FIG. 1C, in a relatively narrow space such as a vehicle cabin, the direct sound, the early reflected sound, and the reverberant sound are not separated at the boundary of the predetermined time Ta, and the direct sound, the early reflected sound, and the reverberant sound do not separate. are mixed. Therefore, as described above, the ratio of the early component A1 to the late component A2 (see FIG. 1B) does not correspond to the ratio of the direct sound or the early reflected sound to the reverberant sound, and there is a risk that the measurement accuracy of the acoustic characteristics will be reduced. .

Here, if the reverberant sound component, which is moderately delayed from the direct sound, is large, for example, the sound image distance R among the acoustic characteristics increases, and the enveloping feeling LEV increases. evaluated. Therefore, as shown in FIG. 1C, in a narrow space such as a vehicle compartment where direct sound and reverberant sound are mixed, the acoustic device positively adds a pseudo-pseudo-reverberant sound G to the direct sound. By doing so, the acoustic characteristics can be improved.

Even in the impulse response of the sound to which the pseudo-reverberant sound G is added in this way, the ratio between the early component A1 and the late component A2 (see FIG. 1B) as described above does not allow the difference between the direct sound, the early reflected sound, and the reverberant sound. There is a possibility that the measurement accuracy of the acoustic characteristics may be lowered.

Therefore, as a result of earnest research, the inventors of the present invention have obtained the knowledge that the acoustic characteristics can be measured with high accuracy by using the threshold obtained from the law of the first wavefront. This will be described with reference to FIG. 1D. Note that FIG. 1D shows the impulse response of the sound to which the pseudo reverberation is added.

As shown in FIG. 1D, first, in the impulse response, a threshold value D obtained from the law of the first wavefront is set. Here, the law of the first wavefront states that, for example, when one of two sounds reaches the listener with a sufficiently small delay with respect to the other sound, the listener hears the one sound that arrives with a delay. It is an imperceptible phenomenon. The above-described threshold value D is obtained from the first wavefront law, and is specifically the boundary of the imperceptible delay. Therefore, a sound delayed by more than the threshold value D is perceived by the listener as an echo sound, for example.

The acoustic device according to the present embodiment divides sound components into a first component E1 including the direct sound and a sound delayed with respect to the direct sound (for example, and a second component E2 containing pseudo reverberation). Since the second component E2 is a component delayed with respect to the threshold value D, the second component E2 includes an echo sound component (hereinafter referred to as an "echo component"). .

The acoustic device then calculates the component ratio based on the second component E2 (echo component). For example, the ratio between the energy component of the entire sound and the second component E2 is calculated as the component ratio. Specifically, the acoustic device calculates the ratio of the overall energy component to the second component E2 as the component ratio.

Note that the overall energy component described above can be calculated, for example, by performing an integration process on the impulse response, but is not limited to this, and may be calculated by other methods. Also, the component ratio is an example of a predetermined value.

The component ratio described above has a correlation with acoustic characteristics such as the sound image width ASW, the sound image distance R, and the enveloping feeling LEV (see later-described FIGS. 3A to 3E). Therefore, in the present embodiment, for example, even in a narrow space such as a vehicle cabin where direct sound and reverberant sound are mixed, even in the case of sound to which pseudo-reverberant sound is added, the above-described Acoustic characteristics can be measured with high accuracy by calculating the component ratio.

Although the component ratio is calculated based on the second component E2 (echo component) in the example shown in FIG. 1D, the present invention is not limited to this. Here, another example of calculating the component ratio will be described with reference to FIG. 1E.

For example, a sound having a relatively large delay with respect to the direct sound is perceived by the listener as a separated sound separated from the direct sound. Since such a separated sound gradually separates as the delay with respect to the direct sound increases, the separated sound includes a separated sound that is partially separated and perceived by the listener depending on the degree of delay (hereinafter referred to as "partially separated sound"). ., see FIG. 1E).

As a result of extensive research, the inventors of the present invention have found that the component of the partially separated sound also has a correlation with the acoustic characteristics, like the second component E2 (echo component) shown in the example of FIG. 1D.

Specifically, as shown in FIG. 1E, first, a threshold value F obtained from the law of the first wavefront is set in the impulse response. The threshold F is the boundary of the delay that becomes part of the separated sound component among the echo components obtained by the threshold D described above. Therefore, a sound delayed by more than the threshold value F is perceived by the listener as a partially separated sound that is separated from the direct sound by a predetermined ratio, for example. In addition, although the above-described predetermined ratio is set to, for example, 50%, it is not limited to this and can be set to any value.

Next, in the impulse response, the acoustic device divides the sound components into a first component E1a including the direct sound and a sound delayed with respect to the direct sound (for example, a partially separated sound ) and a second component E2a containing

The acoustic device calculates the separated component ratio based on the second component E2a including the component of the partially separated sound (hereinafter referred to as "partially separated component"). For example, the audio device calculates the ratio of the energy component of the entire sound and the second component E2a as the separation component ratio. Specifically, the acoustic device calculates the ratio of the overall energy component to the second component E2a as the separation component ratio. Note that the separation component ratio is an example of a predetermined value.

The separation component ratio described above has a correlation with acoustic characteristics such as the feeling of envelopment LEV (see FIG. 3F described later). Therefore, in the present embodiment, for example, even in a narrow space such as a vehicle cabin where direct sound and reverberant sound are mixed, even in the case of sound to which pseudo-reverberant sound is added, the above-described By calculating the separated component ratio, the acoustic characteristics can be measured with high accuracy.

Next, the configuration of an audio system including the audio device according to the first embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration example of an acoustic system including acoustic devices. In FIG. 2, only the components necessary for explaining the features of this embodiment are represented by functional blocks, and the description of general components is omitted.

In other words, each component illustrated in FIG. 2 is functionally conceptual and does not necessarily need to be physically configured as illustrated. For example, the specific forms of distribution and integration of each functional block are not limited to those shown in the figure, and all or part of them can be functionally or physically distributed in arbitrary units according to various loads and usage conditions.・It is possible to integrate and configure.

As shown in FIG. 2 , the audio system 1 includes an audio device 10 , a sound source device 40 , a speaker 50 and an operation section 60 . The sound source device 40 is, for example, a device that outputs a sound source signal of sound including music and voice. Such a sound source signal is input to the acoustic device 10 to generate an output acoustic signal, and the acoustic signal is input to the speaker 50 .

The speaker 50 outputs acoustic signals of sounds generated by the acoustic device 10 . For example, the speaker 50 is arranged in a relatively narrow space such as a passenger compartment of a vehicle, but is not limited to this.

The operation unit 60 receives user's operations on the audio device 10 . For example, the operation unit 60 can receive a change instruction to change the acoustic characteristics to the acoustic characteristics desired by the user through the user's operation. Note that the operation unit 60 outputs a change instruction to the sound device 10, and the sound device 10 executes a process of changing the sound characteristics, which will be described later. As the operation unit 60, for example, a touch panel including a display unit such as a liquid crystal display that can input user's operations and can display various information can be used.

Next, the acoustic device 10 will be described. The audio device 10 includes a storage section 20 and a control section 30 .

The storage unit 20 is realized by, for example, a semiconductor memory device such as a RAM (Random Access Memory) or a flash memory, or a storage device such as a hard disk or an optical disk. Remember.

The index value information 21 includes information on index values indicating acoustic characteristics of sound. Acoustic characteristics include the sound image left-right width ASW1, the sound image front-back width ASW2, the sound image distance R, the enveloping feeling LEV, the sound image clarity C, and the like, and the index values are values indicating these various acoustic characteristics. The information about the index value includes information indicating the correlation between the index value indicating the acoustic characteristics and the above-described component ratio.

Here, the information indicating the correlation included in the index value information 21 will be described with reference to FIGS. 3A to 3F. FIG. 3A is a diagram showing the correlation between the index value of the sound image left-right width ASW1 and the component ratio. FIG. 3B is a diagram showing the correlation between the index value of the sound image front-back width ASW2 and the component ratio. FIG. 3C is a diagram showing the correlation between the index value of the sound image distance R and the component ratio. Also, FIG. 3D is a diagram showing the correlation between the index value of the wrapped feeling LEV and the component ratio. FIG. 3E is a diagram showing the correlation between the index value of the clarity C of the sound image and the component ratio. Further, FIG. 3F is a diagram showing the correlation between the index value of the wrapped feeling LEV and the separation component ratio.

The example of FIG. 3A shows that the index value of the sound image lateral width ASW1 increases as the component ratio decreases, in other words, as the echo component increases. That is, the sound image left-right width ASW1 increases as the number of echo components increases.

The example of FIG. 3B also shows that the index value of the sound image front-back width ASW2 increases as the component ratio decreases, in other words, as the echo component increases. That is, the sound image front-back width ASW2 increases as the number of echo components increases.

Also, the example of FIG. 3C shows that the index value of the sound image distance R increases as the component ratio decreases, in other words, as the number of echo components increases. That is, the sound image distance R increases as the number of echo components increases, in other words, the sound image becomes farther.

Also, in the example of FIG. 3D, the index value of the wrapped feeling LEV increases as the component ratio decreases, in other words, as the echo component increases. index value also decreases. That is, as the number of echo components increases, the enveloping feeling LEV increases once and then gradually decreases.

The example of FIG. 3E also shows that the index value of the sound image clarity C decreases as the component ratio decreases, in other words, as the echo component increases. That is, the sound image clarity C decreases as the number of echo components increases, in other words, the sound image becomes unclear.

Also, the example of FIG. 3F shows that the index value of the wrapped feeling LEV increases as the separated component ratio decreases, in other words, as the partially separated component increases. That is, the wrapped feeling LEV increases as the number of partially separated components increases.

Although FIGS. 3A to 3F specifically show the respective correlations, these are merely examples and are not intended to be limiting. Moreover, each correlation is obtained, for example, through an experiment or the like, but is not limited to this.

Returning to the description of FIG. 2, the control unit 30 is a controller, and is stored in a storage device inside the audio device 10 by, for example, a CPU (Central Processing Unit) or MPU (Micro Processing Unit). Various programs are implemented by executing the RAM as a work area. Also, the control unit 30 can be implemented by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

The control unit 30 includes an acquisition unit 31 , a first calculation unit 32 , a second calculation unit 33 , a sound generation unit 34 and a reception unit 35 .

Acquisition unit 31 acquires a sound source signal output from sound source device 40 . The acquisition unit 31 then transmits the acquired sound source signal to the sound generation unit 34 .

The first calculator 32 calculates a component ratio from the impulse response of sound. For example, the first calculator 32 obtains an impulse response of a sound (an example of a predetermined sound) such as a vehicle interior. Subsequently, the first calculation unit 32 calculates the sound components from the obtained impulse response of the sound by using the threshold value D obtained from the law of the first wavefront, the first component E1 including the direct sound, and and a second component E2 containing the delayed sound (see FIG. 1D).

Then, the first calculator 32 calculates the component ratio based on the second component. Here, since the second component E2 is a component on the side delayed with respect to the threshold value D, it becomes an echo component included in the sound. Since such echo components have a correlation with acoustic characteristics, by calculating the component ratio using the echo components, it is possible to accurately calculate an index value indicating acoustic characteristics, which will be described later.

Further, for example, the first calculator 32 can calculate the ratio between the energy component of the entire sound and the second component as the above-described component ratio. Specifically, the first calculator 32 calculates the ratio of the overall energy component to the second component E2 as the component ratio.

As a result, for example, the relationship (ratio) between the echo component having a correlation with the acoustic characteristic and the overall energy component can be calculated as a component ratio, and the index value to be described later can be calculated with higher accuracy.

The first calculator 32 then outputs information indicating the calculated component ratio to the second calculator 33 . Although an example in which the second component E2 is an echo component has been described above, the second component E2 is not limited to this, and may be, for example, a partially separated component of the echo component.

That is, for example, in the impulse response of the sound, the first calculation unit 32 divides the sound component into a first component E1a including the direct sound and a delay (see FIG. 1E) and a second component E2a containing a sound (for example, a partially separated sound).

Subsequently, the first calculator 32 can calculate the separated component ratio based on the second component E2a including partially separated components. For example, the first calculator 32 can calculate the ratio between the energy component of the entire sound and the second component E2a as the separated component ratio. Specifically, the first calculator 32 calculates the ratio of the overall energy component to the second component E2a as the separation component ratio.

Like the echo component, the partially separated component described above has a correlation with the acoustic characteristics. Therefore, by calculating the separated component ratio using the partially separated component, it is possible to accurately calculate the index value described later. . The first calculator 32 then outputs information indicating the calculated separated component ratio to the second calculator 33 .

The second calculator 33 calculates an index value indicating the acoustic characteristics of the sound based on the component ratio (or the separated component ratio) calculated by the first calculator 32 . For example, the second calculator 33 accesses the index value information 21 in the storage unit 20 and acquires information (see FIGS. 3A to 3F) indicating the correlation between the index value indicating the acoustic characteristics and the component ratio. Then, the second calculator 33 calculates an index value indicating the acoustic characteristic based on the calculated component ratio and the information indicating the correlation. Subsequently, the second calculator 33 outputs information indicating the calculated index value to the sound generator 34 and the receiver 35 .

As described above, in the present embodiment, by using the component ratio calculated using the echo component and the separated component ratio calculated using the partially separated component, the index value indicating the acoustic characteristic can be obtained with high accuracy. can be calculated, in other words, acoustic characteristics can be measured with high accuracy.

Note that, for example, in the impulse response, when the first components E1 and E1a, which are the initial components, do not change and are constant, the first calculator 32 does not calculate the component ratio or the separated component ratio, and obtains the obtained first Information indicating values indicating the two components E2 and E2a may be output to the second calculator 33 . Since the obtained second components E2 and E2a (echo components and partially separated components) have a correlation with acoustic characteristics, the second calculator 33 calculates index values based on the second components E2 and E2a. good too. Even with such a configuration, the index value can be calculated with high accuracy, and the acoustic characteristics can be measured with high accuracy.

The sound generator 34 can generate sound by adding a pseudo-pseudo-reverberant sound to the direct sound (see FIG. 1C). Then, the sound generation unit 34 generates, for example, an acoustic signal for output corresponding to the sound to which the pseudo-reverberation sound is added, and outputs it to the speaker 50 . As a result, the acoustic signal of the sound to which the pseudo reverberation is added is output from the speaker 50 .

As a result, the acoustic characteristics of the acoustic device 10 can be improved. More specifically, by adding the pseudo-reverberant sound, the components of the reverberant sound including the echo component described above are increased, and for example, among the acoustic characteristics, the sound image distance R is increased and the enveloping feeling LEV is increased. It is evaluated that there is a sense of distance and expansiveness, that is, the acoustic characteristics can be improved.

Further, the sound generator 34 can adjust the pseudo-reverberation sound based on the index value indicating the acoustic characteristics. As a result, for example, the acoustic characteristics of the sound in the passenger compartment can be adjusted to the desired acoustic characteristics.

That is, for example, with respect to sound in the vehicle interior, there are cases where the sound image distance R becomes shorter than the desired value or the enveloping feeling LEV falls below the desired value due to the influence of running noise or the like. In such a case, the sound generation unit 34 adjusts the calculated index values indicating the acoustic characteristics such as the current sound image distance R and the enveloping feeling LEV to be the index values indicating the desired acoustic characteristics. to adjust the pseudo-reverberation. As a result, for example, the acoustic characteristics of the sound in the passenger compartment can be adjusted to the desired acoustic characteristics.

Further, the sound generator 34 may adjust the pseudo-reverberation sound while keeping the loudness of the sound constant. Here, the loudness of sound is the overall sound volume in the acoustic device 10 . This makes it possible, for example, to effectively change the acoustic characteristics (for example, to increase the sound image distance R) by adding a pseudo-reverberant sound.

Specifically, for example, if a pseudo-reverberant sound is simply added, the loudness increases by the amount of the added pseudo-reverberant sound. When the loudness (sound volume) increases, the listener perceives that the sound image is closer. That is, even if a pseudo-reverberant sound is added in order to obtain a change in the acoustic characteristics that increases the sound image distance R, if the loudness increases and the sound image distance becomes closer, the acoustic characteristics (here, the sound image distance R) may not be able to change effectively.

Therefore, the sound generation unit 34 adjusts the pseudo-reverberant sound while keeping the loudness of the sound constant, thereby effectively changing the acoustic characteristics, for example, by increasing the sound image distance R by the amount of the pseudo-reverberant sound added. becomes possible.

The reception unit 35 provides the user with information about the index value calculated by the second calculation unit 33, and receives a change instruction to change the index value. For example, the reception unit 35 outputs information about an index value indicating acoustic characteristics to a liquid crystal display (touch panel), which is the operation unit 60, and provides the information to the user. Note that the user is, for example, a listener.

Here, with reference to FIG. 4, information on index values indicating acoustic characteristics provided to the user will be described. FIG. 4 is an explanatory diagram for explaining information about index values indicating acoustic characteristics.

As shown in FIG. 4, information 100 regarding index values is provided and displayed on the liquid crystal display, which is the operation unit 60 . For example, the index value information 100 includes display information for schematically displaying various acoustic characteristics corresponding to the calculated index value by animation, and is a display of a screen on which the setting of the index value can be changed by the user's operation. Contains information.

Specifically, the reception unit 35 displays the sound image left-right width ASW1, the sound image front-back width ASW2, the sound image distance R, the feeling of envelopment LEV, the clarity of the sound image C, etc. by animation so as to correspond to the calculated index values. Let

Then, for example, when the user desires to increase the index value of the sound image distance R, as indicated by arrow H in FIG. performed for Thereby, the receiving unit 35 can receive a change instruction to increase the index value of the sound image distance R. FIG. The accepting unit 35 then outputs the accepted change instruction to the sound generating unit 34 .

The sound generation unit 34 to which the change instruction is input adjusts the pseudo-reverberation sound so that the index value indicating the acoustic characteristics becomes an index value corresponding to the change instruction (so that the index value of the sound image distance R increases). . As a result, the index value of the sound image distance R can be increased, so that the acoustic characteristics can be changed to the acoustic characteristics desired by the user.

Next, a specific processing procedure in the audio device 10 will be described with reference to FIG. FIG. 5 is a flow chart showing a processing procedure executed by the audio device 10. As shown in FIG.

As shown in FIG. 5, the control unit 30 of the acoustic device 10 obtains a second component (e.g., echo component) in the impulse response using a threshold value obtained from the first wavefront law, and the total energy and the second component E2 The component ratio is calculated based on (step S10).

Next, the control unit 30 calculates an index value indicating the acoustic characteristics of the sound based on the calculated component ratio (step S11). Subsequently, the control unit 30 adjusts the pseudo reverberation sound based on the calculated index value (step S13).

As described above, the acoustic device 10 according to the first embodiment includes the first calculator 32 and the second calculator 33 . The first calculator 32 calculates, in the impulse response of the predetermined sound, the components of the predetermined sound using the thresholds D and F obtained from the law of the first wavefront, the first components E1 and E1a including the direct sound, and the A predetermined value (component ratio, separated component ratio) is calculated based on the second components E2 and E2a. The second calculator 33 calculates an index value indicating the acoustic characteristics of the predetermined sound based on the predetermined values (component ratio, separated component ratio) calculated by the first calculator 32 . Thereby, the acoustic characteristics can be measured with high accuracy.

(Second embodiment)
Next, the configuration of the acoustic device 10 according to the second embodiment will be described with reference to FIG. 6A and subsequent figures. In addition, below, about the structure common to 1st Embodiment, the same code|symbol is attached|subjected and description is abbreviate|omitted.

For example, a relatively narrow space such as a passenger compartment is an acoustic space in which it is difficult to sufficiently obtain reverberant sound due to wall surface reflection of direct sound. Therefore, by adding the above-described pseudo-reverberant sound to the direct sound, it is possible to improve, for example, the feeling of envelopment. However, when the reverberation increases, the sound image tends to become unclear.

Therefore, in the second embodiment, both the clarification of the sound image and the enhancement of the feeling of envelopment are achieved.

First, an overview of the sound control method for the sound device 10 according to the second embodiment will be described with reference to FIGS. 6A to 6D. FIG. 6A is a diagram showing impulse responses for each band in home audio. FIG. 6B is a diagram showing the amplitude of sound pressure in car audio. FIG. 6C is a diagram showing impulse responses for each band in car audio. FIG. 6D is a schematic explanatory diagram of the acoustic control method according to the second embodiment.

Specifically, FIG. 6A shows impulse responses for each low, middle, and high frequency range in home audio installed in a relatively large space such as a listening room. In the case of home audio, etc. (also possible in concert halls, etc.), as shown in M1 and M2 in FIG. 6A, the attenuation of direct sound energy is steep in the middle and high frequencies. That is, in such a case, the direct sound and the reverberant sound are relatively separated, and the listener can perceive a small and clear sound image width ASW and a large enveloping feeling LEV.

On the other hand, in the case of a car audio system installed in a relatively narrow space such as a vehicle interior, due to the characteristics of the closed space of the vehicle and the running noise of the vehicle, as shown in FIG. are mixed and slightly diffused, the listener L is likely to perceive a large and unclear sound image width ASW. That is, the listener L tends to perceive that the sound quality is poor.

If a pseudo-reverberation sound is added as a late component, the enveloping feeling LEV increases, but the sound quality may be further deteriorated by being mixed with the early component. As shown in FIG. 6C, looking at the impulse responses for each of the low, middle, and high frequencies, the middle frequencies such as vocals tend to mix reverberation, Noticeable change or drop in timbre.

In addition, as indicated by M4 in the figure, in the low frequency range, the trailing edge of the early component interferes with the late component, and the low frequency may disappear or be emphasized. In the case of car audio, it is often designed to emphasize the bass so as not to be buried in the noise inside the car, in which case the above tendency becomes even more pronounced. In this way, in the case of car audio, early components and late components tend to mix in the low to mid range, and the sound image width ASW tends to increase. is difficult.

In the case of car audio, there are cases where signal processing is used to extract uncorrelated components of the left and right channels of the sound source S and add reverberation. Musical instruments, etc. may be heard unnaturally indistinctly.

Therefore, in the acoustic control method according to the second embodiment, group delay control of impulse response according to frequency is performed. Specifically, as shown in FIG. 6D, in the acoustic control method according to the second embodiment, the initial component is delayed as the frequency increases. On the other hand, the lower the frequency, the later the late component corresponding to the pseudo-reverberation sound is delayed.

As a result, it is possible to eliminate the phenomenon in which the early components and the late components tend to be mixed in the low to middle frequencies, so that the early components and the late components can be easily separated over the entire frequency band. Therefore, according to the sound control method according to the second embodiment, it is possible to achieve both the clarification of the sound image and the enhancement of the enveloping feeling LEV.

In addition, since the initial component and the late component can be easily separated over the entire frequency band, it is possible to clearly hear only vocals, etc., as in the case of adding reverberation to the uncorrelated components of the LR channels of the sound source S described above. It is possible to make it difficult to give an unnatural auditory impression.

A configuration example of the acoustic device 10 to which the acoustic control method according to the second embodiment described above is applied will be described below more specifically.

FIG. 7 is a block diagram showing a configuration example of the acoustic device 10 according to the second embodiment. 8A and 8B are schematic diagrams showing acoustic effects obtained by the acoustic device 10. FIG. Note that FIG. 7 mainly illustrates the sound generation unit 34 of the acoustic device 10, and omits other descriptions such as the acquisition unit 31. As shown in FIG.

As shown in FIG. 7, the speaker 50 according to the second embodiment includes a left front speaker FL, a right front speaker FR, a left rear speaker RL, and a right rear speaker RR. The acoustic device 10 receives the sound source signals of the LR channels input from the sound source device 40, generates acoustic signals for output, and outputs the left front speaker FL, the right front speaker FR, the left rear speaker RL, and the right rear speaker. output from each of the RRs. These speakers are hereinafter simply referred to as speakers FL, FR, RL, and RR.

These speakers FL, FR, RL, and RR are arranged in a vehicle compartment 200 of the vehicle C, as shown in FIG. 8, for example. The acoustic device 10 according to the second embodiment localizes and clarifies the sound image of the early components in front of the listener L seated in the vehicle compartment 200, and surrounds the listener L with the sound image of the late components, that is, wraps the sound image. This is intended to enhance the rareness LEV.

Returning to the description of FIG. 7, the sound generation unit 34 of the acoustic device 10 includes a high-frequency delay processing unit 34a, a reverberation processing unit 34b, a low-frequency delay processing unit 34c, a D/A conversion unit 34d, an amplified output 34e, and implements or executes the information processing functions and actions described below.

The high-frequency delay processing unit 34a performs group delay control processing for delaying the sound source signal, which is the initial component, as the frequency increases, such that the higher the frequency, the higher the delay. Specific contents will be described later with reference to FIG. Note that the high-frequency delay processing unit 34a is an example of a first processing unit.

The reverberation processing unit 34b performs reverberation processing on the sound source signal, which is the late component corresponding to the pseudo-reverberation sound. For reverberation processing, for example, an FIR (Finite Impulse Response) filter, an IIR (Infinite Impulse Response) filter, or the like can be used.

The low-frequency delay processing unit 34c performs group delay control processing for delaying the reverberated late-stage component as the frequency becomes lower, such that the lower the frequency, the lower the delay. Specific contents will be described later with reference to FIG. It should be noted that the low frequency delay processing unit 34c is an example of a second processing unit.

The D/A converter 34d D/A-converts the initial component signal that has been subjected to high-frequency delay processing by the high-frequency delay processor 34a. The D/A converter 34d D/A-converts the late component signal that has undergone reverberation processing by the reverberation processing unit 34b and low-frequency delay processing by the low-frequency delay processing unit 34c. Note that the early component signal is an example of the second acoustic signal, and the late component signal is an example of the second acoustic signal.

The amplification output unit 34e amplifies the initial component signal and the late component signal D/A-converted by the D/A conversion unit 34d, and outputs the initial component signals from the speakers FL and FR. Also, late component signals are output from the speakers RL and RR.

Next, the details of the high-frequency delay processing executed by the high-frequency delay processing section 34a and the low-frequency delay processing executed by the low-frequency delay processing section 34c will be specifically described with reference to FIG. FIG. 9 is an explanatory diagram of high-frequency delay processing and low-frequency delay processing.

As shown in FIG. 9, in the high-frequency delay processing, "group delay control" is performed to delay the initial component as the frequency increases. In such "group delay control", as indicated by "band selection" in the figure, only the band desired to be changed may be shifted.

In addition, in the high-frequency delay processing, as shown in the "sweep signal (low to high)" in the figure, by using an FIR filter or IIR filter that sweeps the initial component from low to high frequencies, the high frequency delay as much as

In addition, in the high-frequency delay processing, as shown in the "steep fall" in the figure, for example, by using an inverse filter that offsets the impulse response up to the listening position of the listener L, the fall of the initial component is reduced. sharpen. This makes it easier to separate the early component and the late component. Since the characteristics of each listening position in the passenger compartment 200 can be known in advance for each vehicle type, an inverse filter corresponding to such characteristics may be set.

Although not shown in FIG. 9, in the high-frequency delay processing, the tone quality of the initial component is adjusted so that the peaks of the initial component for each frequency line up in the sense of hearing (see axis Pp in FIG. 6D). can be prevented from deteriorating, and the sound quality can be improved. It should be noted that it is not always necessary to correct the peaks so that they line up in a row.

Subsequently, as shown in FIG. 9, in the low-band delay processing, "group delay control" is performed to delay the later components as the frequency becomes lower. In such "group delay control" as well, it is also possible to shift only the band desired to be changed (see "band selection" in the figure), as in the case of the high frequency band described above.

In addition, in the low-frequency delay processing, as shown in the "sweep signal (high→low)" in the figure, the low-frequency delay as much as

Also, in the low-frequency delay processing, the pitch of the late component may be slightly shifted higher than the pitch of the initial component, as indicated by "higher frequency than initial component" in the figure. In other words, in this case, instead of temporally delaying the low frequency band, the temporally delayed band is controlled by shifting the frequency. Note that such temporal and frequency controls may be combined as appropriate.

Further, in the low-frequency delay processing, as indicated by "ALL-PASS FILTER" in the figure, by using an all-pass filter for the later components, the lower frequencies can be delayed. By using the all-pass filter, it is possible to delay the lower frequencies while changing only the phase characteristics without changing the amplitude characteristics.

In addition, in the low-band delay processing, a reverberation FIR filter that delays the rise of the late component by using a window function or the like may be used, as indicated by "delayed rise" in the figure. This makes it easier to separate the early component and the late component.

In addition, in the low-frequency delay processing, the late component may be smoothed as indicated by "smoothing" in the figure. Such smoothing makes it possible to move the reverberation away by gradually changing the late component, thereby facilitating the separation of the early component and the late component.

It should be noted that the high-frequency delay processing and low-frequency delay processing shown in FIG. 9 can be appropriately combined within a range that does not contradict the processing contents. In addition, the delay time and the like may be controlled by the physical arrangement of the speakers instead of the information processing by the high-frequency delay processing and the low-frequency delay processing. For example, it is possible to control the delay time and the like according to the reproduction band of each speaker, such as placing the woofer for bass reproduction at a position far from the listening position of the listener L. FIG.

Further, the speakers FL and FR for outputting the initial components, for example, may be speakers provided with filters for removing reflected sounds, not limited to the reproduction band.

Next, a processing procedure executed by the audio device 10 according to the second embodiment will be described with reference to FIG. 10 . FIG. 10 is a flow chart showing a processing procedure executed by the audio device 10 according to the second embodiment.

As shown in FIG. 10, first, the high-frequency delay processing unit 34a performs high-frequency delay processing on the initial component (step S101). After the reverberation processing unit 34b performs reverberation processing on the late component corresponding to the pseudo-reverberation sound (step S102), the low-frequency delay processing unit 34c performs low-frequency delay processing (step S103).

Then, the D/A conversion unit 34d applies D/A conversion processing to each of the high-frequency delay-processed early component signal and the low-frequency delay-processed late component signal (step S104). Then, the amplification output unit 34e performs amplification processing on each signal after the D/A conversion processing (step S105), outputs the amplified signals to the speakers FL, FR, RL, and RR, and ends the processing.

Up to this point, the amplification output unit 34e outputs early component signals from the speakers FL and FR, and outputs late component signals from the speakers RL and RR. may be output from the speakers FL and FR. Alternatively, the early component signal may be synthesized with the late component signal and output from the speakers RL and RR.

Also, in FIG. 10, an example was given in which the processing systems for the initial component and the late component are executed in parallel, but these processing systems may be executed serially.

As described above, in the audio device 10 according to the second embodiment, the sound generation section 34 includes the high frequency delay processing section 34a and the low frequency delay processing section 34c. Based on the sound source signal, the high-frequency delay processing unit 34a generates an initial component signal which is delayed as the frequency becomes higher and is output so as to be localized in front of the listener L. FIG. Based on the sound source signal, the low-frequency delay processing unit 34c generates a second acoustic signal corresponding to the pseudo-reverberation sound, which is a late component signal that is delayed as the frequency becomes lower and that is output from the surroundings of the listener L. Therefore, according to the acoustic device 10 according to the second embodiment, both the clarification of the sound image and the enhancement of the enveloping feeling can be achieved.

Further, the high-frequency delay processing unit 34a generates an initial component signal by delaying the initial component of the sound source signal including the direct sound as the frequency increases. Therefore, according to the audio device 10 according to the second embodiment, the higher the frequency of the sound source signal, the more delayed the initial component of the sound source signal, so that the initial component and the late component can be easily separated.

In addition, the high-frequency delay processing unit 34a delays the initial component as the frequency increases by filtering the sweep signal that changes from low-frequency to high-frequency with respect to the initial component. Therefore, according to the acoustic device 10 according to the second embodiment, it is possible to easily delay the initial component as the frequency is higher by filtering.

Further, the high-frequency delay processing unit 34a generates an initial component signal such that the initial component has a sharp fall. Therefore, according to the acoustic device 10 according to the second embodiment, it is possible to easily separate the early component and the late component.

Further, the low frequency band delay processing unit 34c delays the late component of the sound source signal corresponding to the reverberant sound as the frequency becomes lower by filtering the sweep signal that changes from the high frequency to the low frequency. Therefore, according to the acoustic device 10 according to the second embodiment, it is possible to easily delay the later component as the frequency is lower by filtering.

Also, the low frequency band delay processing unit 34c generates the late component signal so that the rise of the late component is delayed. Therefore, according to the acoustic device 10 according to the second embodiment, the early component and the late component can be easily separated.

Further, the acoustic device 10 according to the second embodiment includes speakers FL and FR arranged in front of the listener L (corresponding to an example of "front speakers") and speakers RL and RR arranged behind the listener L. (corresponding to an example of a "rear speaker"), and an amplification output section 34e (corresponding to an example of an "output section") that outputs the early component signal and the late component signal from the speakers FL, FR and the speakers RL, RR. The amplified output unit 34e outputs the early component signals from the speakers FL and FR, and outputs the late component signals from the speakers RL and RR. Therefore, according to the acoustic device 10 according to the second embodiment, the sound image due to the early components is clarified in front of the listener L seated in the vehicle compartment 200, and the sound image due to the late components around the listener L, that is, the envelope. Rare feeling LEV can be enriched.

Further, the amplification output unit 34e synthesizes the late component signal with the early component signal and outputs it from the speakers FL and FR, and synthesizes the early component signal with the late component signal and outputs it from the speakers RL and RR. Therefore, according to the acoustic device 10 according to the second embodiment, it is possible to localize a clear and expansive sound image in front of the listener L, and to resonate a natural sound with a large feeling LEV wrapped around the listener L. can.

In each of the above-described embodiments, the case where the acoustic device 10 is mounted in a vehicle is taken as an example. It can be installed in various spaces regardless of whether it is a moving object or not.

Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the invention are not limited to the specific details and representative embodiments so shown and described. Accordingly, various changes may be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and equivalents thereof.

1 sound system 10 sound device 32 first calculator 33 second calculator 34 sound generator 34a high frequency delay processor 34c low frequency delay processor 35 reception unit

Claims (9)

In the impulse response of the predetermined sound, the components of the predetermined sound are divided into a first component including the direct sound and a second component including the sound delayed with respect to the direct sound by a threshold value obtained from the law of the first wavefront. a first calculation unit that divides and calculates a predetermined value based on the second component;
and a second calculator that calculates an index value indicating acoustic characteristics of the predetermined sound based on the predetermined value calculated by the first calculator. The first calculator,
2. The acoustic device according to claim 1, wherein a ratio of the energy component of the entire predetermined sound and the second component is calculated as the predetermined value. The second component is
3. The acoustic device according to claim 1, wherein the echo component is included in the predetermined sound. The second component is
3. The acoustic apparatus according to claim 1, wherein the acoustic device is a partially separated component that is partially separated and perceived by a listener of the predetermined sound, among the echo components included in the predetermined sound. a sound generation unit that generates the predetermined sound by adding a pseudo-pseudo-reverberant sound to the direct sound;
The sound generation unit
The acoustic device according to any one of claims 1 to 4, wherein the pseudo reverberation sound is adjusted based on the index value calculated by the second calculator. The sound generation unit
6. The acoustic device according to claim 5, wherein the pseudo-reverberant sound is adjusted while keeping the loudness of the predetermined sound constant. a reception unit that provides information about the index value calculated by the second calculation unit and receives a change instruction to change the index value,
The sound generation unit
The acoustic device according to claim 5 or 6, wherein the pseudo reverberation sound is adjusted so that the index value corresponds to the change instruction received by the reception unit. The sound generation unit
a first processing unit that generates a first acoustic signal based on the sound source signal, which is delayed as the frequency is higher and is output so as to be localized in front of the listener;
A second processing unit that generates the second acoustic signal corresponding to the pseudo-reverberation sound, which is a second acoustic signal that is delayed as the frequency is lower and is output from the surroundings of the listener based on the sound source signal. 8. The acoustic device according to any one of claims 5 to 7, comprising: In the impulse response of the predetermined sound, the components of the predetermined sound are divided into the first component including the direct sound and the second component including the sound delayed with respect to the direct sound, according to the threshold value obtained from the law of the first wavefront. a first calculation step of dividing and calculating a predetermined value based on the second component;
and a second calculation step of calculating an index value indicating characteristics of the predetermined sound based on the predetermined value calculated in the first calculation step.

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