JP2003122378A - Audio reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an audio reproducing device in which no effect is received from reverberation characteristics that are unique to a room and same surrounding effect is obtained in any room. SOLUTION: In the device which reproduces audio signals and supplies the signals to a speaker 1, a reverse filter 5b is provided to cancel the reverberation characteristics of the space in which the speaker is located and the audio signals are supplied to the speaker 1 through the filter 5b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio playback device suitable for surround playback.

[0002]

2. Description of the Related Art Conventionally, in an audio reproducing apparatus for reproducing an audio signal from a sound source such as a CD (Compact Disc) and outputting the audio signal to a speaker, for example, a DSP (di
It has been proposed to perform so-called surround reproduction such as "concert hall" or "live house" by performing signal processing by a gital signal processor). During this surround reproduction, the listener can feel as if he / she was in the room, as if he were there.

[0003]

By the way, even when the same audio source is used for surround reproduction and listening, the surround effect is different depending on the room. This has the reverberation characteristic peculiar to each room,
This is because this reverberation characteristic has been added to the surround sound.

As shown in FIG. 5, in general, when a sound wave emitted from a speaker is heard, in addition to the direct sound coming directly from the speaker 1 to the listener's ear, not only the wall or ceiling constituting the room 3 is heard. The reflected sound is reflected and arrives with a slight delay, and the reverberant sound diffused by repeating the reflection is received. Usually, the reflection state of the sound wave changes depending on the volume of the room, the hardness of the wall, etc., so the way the listener hears the sound also changes. This is called the reverberation characteristic of the room.

However, in order to cancel the reverberation of a room, the reverberation characteristic of this room is required, but a special device is required to measure this reverberation characteristic, and it is measured at a general home. Is not realistic.

In view of the above point, the present invention has an object to obtain a similar surround effect in any room without being affected by the reverberation characteristic peculiar to the room.

[0007]

The audio reproducing apparatus of the present invention is an audio reproducing apparatus for reproducing an audio signal and supplying the audio signal to a speaker. The audio reproducing apparatus includes an inverse filter for canceling the reverberation characteristic of the space where the speaker is arranged. The audio signal is supplied to the speaker through the inverse filter.

According to the present invention, since the inverse filter for canceling the reverberation characteristic of the space where the speaker is arranged is provided and the audio signal is supplied to the speaker through the inverse filter, the reverberation characteristic peculiar to the room is canceled. A desired surround effect can be obtained.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an audio reproducing apparatus according to the present invention will be described below with reference to FIGS. In FIG. 1, parts corresponding to those in FIG. 5 are designated by the same reference numerals.

In FIG. 1, reference numeral 4 denotes, for example, a CD (Compact
The audio signal from the sound source 4 such as a CD is supplied to the signal processing means 5a which constitutes the audio reproducing apparatus main body 5 and which surrounds the audio signal, for example. An inverse filter that has an acoustic transfer function H (z) -1 that is the opposite of the acoustic transfer function H (z) that reproduces the reverberation characteristic of the room disposed downstream of the signal processing means 5a and that cancels the reverberation characteristic of the room. The speaker 2 is supplied to the speaker 1 through 5b so that the listener 2 can hear the sound from the speaker 1.

The signal processing means 5a is, for example, a surround mode display 5c arranged in the audio reproducing apparatus main body 5.
For example, a surround mode such as "concert hall" or "live house" is selected, and the signal processing setting of the signal processing means 5a is switched according to the selected surround mode to perform signal processing so as to obtain a desired surround effect. I will do it.

Further, the inverse filter 5b is, for example, a room model display 5d arranged on the audio reproducing apparatus main body 5 from among a plurality of room models preset by the listener 2 which is close to an actual room configuration. It is determined by selecting and switching the acoustic transfer function of the inverse filter 5b according to the selected room model. For example, several dozen types of room models and corresponding inverse filters are prepared.

Now, with reference to FIG. 2, a method of forming an inverse filter by a known technique will be described.

First, the reverberation characteristic of the object to be canceled, which is the source of the inverse filter, is required. The acoustic transfer function that determines the reverberation characteristics is that the speaker is placed in the room, an impulse sound is emitted from this speaker, and the impulse at the listening point located on the opposite side of the room to which the impulse sound reaches. It can be determined by measuring the response. That is, the impulse response measured at the listening point is the acoustic transfer function from the speaker that emits the impulse sound to the listening point, and becomes the reverberation characteristic of this room.

By the way, regarding the above-mentioned acoustic transfer function, there are data under various conditions such as the difference in the reflection state of sound waves depending on the volume of the room, the type of wall, etc. The data can be obtained by simulation using a computer. For example, when conditions such as 10 tatami mat, height 2 m, wall concrete, etc. that constitute a room are input, a computer simulation is performed from these conditions to calculate the acoustic transfer function of this room. Then, an FIR (finite impulse response) filter 5b 'that reproduces the reverberation characteristics of the room can be created based on the calculated acoustic transfer function.

Next, an inverse FIR for canceling the effect of the FIR filter for reproducing the reverberation characteristic of the room obtained as described above.
Create a filter. In FIG. 2, for an arbitrary input signal L1 from the input terminal 20, the input signal L1 and a filter 5b ′ and an inverse filter 5b that reproduce the reverberation characteristics of the room
And the output signal L2 of the system in which are arranged in series are input to the adder circuit 21, and the difference output signal L3 is obtained at the output terminal 22.

At this time, the input signal L1 and the output signal L2 of the system in which the filter 5b 'for reproducing the reverberation characteristic of the room and the inverse filter 5b are arranged in series are input to the adder circuit 21 and the output signal L3 of the difference is obtained. The parameter that determines the specifications of the inverse filter 5b is adjusted based on the feedback from the output signal L3 so that it becomes zero.

Then, the output signal L3 is adjusted as described above.
When becomes zero, the acoustic transfer function H (z) -1 of the inverse filter 5b that cancels the reverberation characteristic of the filter 5b 'is determined.

FIG. 3A shows an example of the acoustic transfer impulse response H in a certain sound field. The horizontal axis represents the number of points (P) sampled at, for example, 44.1 kHz and corresponds to the time axis, and the vertical axis represents the relative value of the amplitude. FIG. 3A shows a state in which a blank (about 400 P) from the point where the impulse sound is emitted to the point where the sound reaches the listening point is left, one shot is sharply raised, and then gradually attenuated.

Further, FIG. 3B shows an example of the acoustic transfer impulse response H-1 of the inverse filter with respect to the acoustic transfer impulse response H of a certain sound field shown in FIG. 3A. Similar to FIG. 3A, the horizontal axis represents the number of points (P) sampled at 44.1 kHz and corresponds to the time axis, and the vertical axis represents the relative value of amplitude. As shown in FIG. 3B, the impulse response H-1 of the inverse filter is symmetrical with respect to the rising edge of the impulse and is gradually attenuated from this rising point on the basis of the rising edge of the impulse.

FIG. 4 shows the impulse responses of FIGS. 3A and 3B on the frequency axis. Horizontal axis is frequency
(Hz) and the vertical axis show the amplitude (dB), and the amplitude on the vertical axis is a relative value. In FIG. 4, the frequency characteristic in a certain sound field and the frequency characteristic of the inverse filter are substantially symmetrical with respect to 0 (dB) as the object axis, and are made to cancel each other out.

Therefore, in this example, the prepared 10
For the reverberation characteristics of several types of room models, the inverse filters 5b are created by the above-described method, and the data about the inverse filters 5b corresponding to each room model is written to the ROM mounted in the audio reproducing apparatus main body 5, for example. (Remembered) so that the inverse filter 5b corresponding to the room model selected on the room model display 5d can be read out.

Since this example is constructed as described above, for example, C
When the audio signal from the sound source 4 such as a D (Compact Disc) is reproduced by the audio reproducing device, the listener 2 can change the surround mode preset in the surround mode display 5c arranged on the audio reproducing device 5 from the surround mode. For example, a desired surround mode such as "concert hall" or "live house" is selected. Then, the audio signal supplied to the signal processing means 5a for performing the surround processing on the audio signal forming the main body of the audio reproducing device 5 is subjected to the surround processing according to the selected surround mode. The surround-processed audio signal is supplied to the inverse filter 5b that cancels the reverberation characteristic of the room arranged downstream of the signal processing means 5a. In the inverse filter 5b, the acoustic transfer function according to the room model selected in the room model display 5d is called and signal processing is performed so as to cancel the reverberation characteristic of the room. Then, the audio signal subjected to the signal processing so as to cancel the reverberation characteristic of the room is supplied to the speaker 1 and emitted.

While the sound emitted from the speaker 1 reaches the listener 2, the reverberation characteristic of the room represented by the acoustic transfer function H (z) is added. However, the acoustic transmission that cancels the reverberation characteristic of the room in advance is added. Since the reverberation characteristic of the room is canceled by the inverse filter 5b having the function H (z) -1, the listener 2 can only listen to the sound that has been subjected to the surround processing with respect to the original sound source. it can.

In the ROM mounted on the audio reproducing apparatus main body 5, the reverberation models of a plurality of rooms and the inverse filter 5b corresponding thereto are prepared as described above, and the listener 2
Selects the room model closest to the actual room from the preset room models. By applying the inverse filter 5b that cancels the reverberation characteristic of the room based on the selected room model, the same effect can be obtained in any room without being affected by the reverberation characteristic unique to the room. You can hear the sound of.

As described above, according to this example, the inverse filter having the acoustic transfer function for canceling the reverberation characteristic of the room in which the speaker is arranged is provided, and the audio signal is supplied to this speaker through the inverse filter. As a result, the reverberation characteristic peculiar to the room is canceled and the desired surround effect can be obtained.

Further, by preparing a plurality of inverse filters so that the inverse filter can be selected based on the structure of the room, the same reverberation can be heard in any room without being affected by the reverberation characteristic peculiar to the room. You can hear the sound.

In this example, the volume of the room, the type of the floor and the type of the wall are mentioned as the conditions for constructing the room for simulating the reverberation characteristic. Various conditions are conceivable within the range permitted by the memory capacity of the ROM for writing (storing).
In this case, it is possible to preset a room model having reverberation characteristics that more closely match the actual room.

Although the room model is selected based on the room configuration, a room model which is different from the actual room configuration and which allows the listener to listen to his / her own ear and obtain a comfortable surround reproduction. It may be set to.

Further, in this example, the reverberation characteristic model of the room is preset in the audio reproducing apparatus, but the reverberation of the room may be measured at a general home if the equipment is ready. That is, the result of measuring the reverberation characteristic is recorded in a recording medium such as a memory card and the memory card is sent to the maker, or the measured data is sent to the maker using the Internet or the like. The manufacturer creates an inverse filter that cancels the reverberation in the room based on the reverberation characteristics sent to it, and sends it back to the client at a later date. Then, for example, the data of the inverse filter may be written (stored) in a ROM or the like in the audio reproducing apparatus and incorporated in the audio reproducing apparatus to cancel the reverberation unique to the room.

Furthermore, the present invention is not limited to the above-mentioned examples, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0032]

According to the present invention, an inverse filter having an acoustic transfer function for canceling the reverberation characteristic of the room in which the speaker is arranged is provided, and the audio signal is supplied to the speaker through the inverse filter. , The reverberation characteristic peculiar to the room is canceled, and there is a benefit that the desired surround effect can be obtained.

By providing a plurality of inverse filters so that the inverse filter can be selected based on the room structure, the same reverberation characteristics can be obtained in any room without being affected by the reverberation characteristic peculiar to the room. There is a benefit of being able to hear the audio.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an embodiment of an audio reproducing apparatus of the present invention.

FIG. 2 is a diagram for explaining the creation of an inverse filter.

FIG. 3 is a diagram showing an example of an impulse response of a certain sound field and its inverse filter.

FIG. 4 is a diagram showing an example of frequency characteristics of each impulse response in FIG.

FIG. 5 is a diagram showing how sound is reflected in a room.

[Explanation of symbols]

1 ... Speaker, 2 ... Listener, 4 ... Sound source, 5 ... Audio reproduction apparatus main body, 5a ... Signal processing means, 5b ...
..Inverse filters, 5b '... Filters, 5c ... Surround mode display, 5d ... Room model display

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Taketoshi Yazaki             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 5D020 CC04 CC06                 5D062 AA22                 5D108 AA01 AA03 AA08 AD09

Claims (2)

[Claims] 1. An audio reproducing apparatus adapted to reproduce an audio signal and supply it to a speaker, comprising an inverse filter for canceling a reverberation characteristic of a space in which the speaker is arranged, and passing the audio signal through the inverse filter to the speaker. An audio reproducing device characterized in that it is adapted to be supplied to. 2. The audio reproducing apparatus according to claim 1, wherein the inverse filter is selected from a plurality of inverse filters prepared based on the configuration of the space.