JP4339420B2 - Audio playback device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an audio playback apparatus having a playback function for multi-channel audio signals.
[0002]
[Prior art]
Recently, it is assumed that audio signals associated with movies and other images are multi-channeled and reproduced by speakers placed on the front left and right and center front of the listener, and speakers placed on the left and right rear or both sides of the listener. It is recorded as. According to this, the sound field in the video matches the position of the sound image actually heard, and a sound field having a more natural spread is established.
[0003]
However, when such a sound is viewed using headphones, the sound image is localized in the head, and the direction of the image does not match the localization position of the sound image, resulting in a very unnatural sound image localization. Furthermore, the localization position of the audio signal of each channel cannot be reproduced separately and independently. Of course, the same applies when listening to multi-channel sound such as musical sounds. Unlike the case of speaker playback, the sound can be heard from within the head, the localization of the sound image is not separated, and the sound field playback is extremely unnatural. turn into.
[0004]
Therefore, a method is conceivable in which a transfer function from each speaker to the listener's ears is measured or calculated in advance, convolved with an audio signal by a filter such as a digital filter, and then listened to through headphones. According to this method, the sound image is localized outside the head, and a sound field equivalent to that in the case of speaker reproduction can be reproduced.
[0005]
[Problems to be solved by the invention]
However, in this method, it is necessary to prepare a filter for each transfer function from each speaker to the listener's both ears, and the amount of calculation of the impulse response becomes very large, so that the apparatus is large and expensive. turn into.
[0006]
In view of the above, the present invention realizes a reproduction sound field equivalent to that of speaker reproduction using headphones, and simplifies the configuration.
[0007]
[Means for Solving the Problems]
In this invention,
The input audio signal is a four-channel audio signal supplied to each speaker arranged at the left front, right front, left rear, and right rear of the listener, and a predetermined reproduction sound field is generated by the reproduction sound of the speaker. When the audio signal to be formed,
A first signal processing circuit for converting the input audio signal into a two-channel audio signal according to a first transfer function;
A second signal processing circuit for converting the two-channel audio signal output from the first signal processing circuit according to a second transfer function;
A terminal for outputting the two-channel audio signal output from the first signal processing circuit to the outside ;
When the two-channel audio signals output from the first signal processing circuit are supplied to two speakers arranged at the left front and right front of the listener, the first signal processing circuit The input audio signal is converted into the two-channel audio signal so that a reproduction sound field equivalent to the field is formed,
The second signal processing circuit has a reproduction sound field obtained when the two-channel audio signal is supplied to the two speakers when the output audio signal of the second signal processing circuit is supplied to the headphones. The two-channel audio signal is converted into the output audio signal so that a reproduction sound field equivalent to the above is formed,
The audio reproduction apparatus is configured to supply the output audio signal of the second signal processing circuit to the headphones to obtain a reproduction sound field by the 4- channel audio signal.
Therefore, the original 4-channel audio signal is converted into a 2-channel audio signal that provides a reproduction sound field equivalent to that of the 4-channel reproduction by the speaker, and then a reproduction sound field equivalent to that of the speaker reproduction is obtained. It is converted into an audio signal for headphones to be obtained and supplied to the headphones.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, reference numeral 10 denotes one form of an audio reproducing apparatus according to the present invention. The codes SLF, SRF, SLB, and SRB are four-channel audio signals. These signals SLF, SRF, SLB, and SRB are sent to the speakers arranged at the left front, right front, left rear, and right rear of the listener. When each is supplied, a 4-channel stereo playback sound field is realized.
[0009]
These audio signals SLF to SRB are supplied to the A / D converter circuits 21 to 24 through the input terminals 11 to 14 and A / D converted, and the A / D converted audio signals SLF to SRB are, for example, This is supplied to the first digital processing circuit 3 constituted by a DSP. Although details of the digital processing circuit 3 will be described later, this converts the audio signals SLF to SRB into audio signals SL3 and SR3 that can obtain sound image localization of four channels with two speakers.
[0010]
That is, in the digital processing circuit 3, when the signals SL3 and SR3 are supplied to the speakers arranged at the left front and right front of the listener, the signals SLF, SRF, SLB and SRB are left front, right front and left rear of the listener. The signals SLF to SRB are converted into signals SL3 and SR3 so as to realize a reproduction sound field equivalent to the reproduction sound field obtained when supplied to a speaker arranged on the right rear side (at this time point). The audio signals SLF to SRB are digital signals, but are described as analog signals because they are complicated to describe.
[0011]
The signals SL3 and SR3 from the digital processing circuit 3 are supplied to the second digital processing circuit 4. The digital processing circuit 4 is also constituted by a DSP, for example, and converts the audio signals SL3 and SR3 into audio signals SL4 and SR4 that can obtain sound image localization outside the head when listened to through headphones. That is, the digital processing circuit 4 is equivalent to the reproduced sound field obtained when the signals SL4 and SR4 are supplied to the headphones and when the signals SL3 and SR3 are supplied to the speakers arranged on the left front and right front of the listener. The signals SL3 and SR3 are converted into signals SL4 and SR4 so as to realize the reproduced sound field.
[0012]
The audio signals SL4 and SR4 are supplied to the D / A converter circuits 5L and 5R and D / A converted. The D / A converted audio signals SL4 and SR4 are output from the headphones 7 through the headphone amplifiers 6L and 6R. Supplied to the left and right acoustic units 7L, 7R.
[0013]
According to such a configuration, the audio signals SL4 and SR4 supplied to the headphones 7 are signals obtained by converting the audio signals SL3 and SR3 so that the sound image localization in the case of speaker reproduction can be obtained even with the headphones 7. The audio signals SL3 and SR3 are signals obtained by converting the 4-channel audio signals SLF to SRB so that a 4-channel sound image localization can be obtained even with two speakers.
[0014]
Therefore, even with the headphones 7, it is possible to realize a reproduction sound field equivalent to the case where audio reproduction is performed by supplying four-channel audio signals SLF to SRB to four speakers.
[0015]
Next, a process in which the digital processing circuit 3 converts the number of channels of the reproduction sound field by the speaker will be described. In this case, the digital processing circuit 3 is constituted by a discrete circuit.
[0016]
Now, as shown in FIG. 2, the sound sources SL and SR are arranged at the left front and right front of the listener LSNR, and the sound source SX is equivalently reproduced at an arbitrary position outside the head by these sound sources SL and SR. Think. And
HLL: Transfer function from sound source SL to left ear of listener LSNR HLR: 〃 Right ear 〃
HRL: Transfer function from sound source SR to the left ear of listener LSNR HRR: 右 Right ear 〃
HXL: Transfer function from sound source SX to the left ear of listener LSNR HXR: ： Right ear 耳
Then, the sound sources SL and SR are
SL = (HXL × HRR−HXR × HRL) / (HLL × HRR−HLR × HRL) × SX
(1)
SR = (HXR × HLL−HXL × HLR) / (HLL × HRR−HLR × HRL) × SX
(2)
It can be expressed as
[0017]
Therefore, the input audio signal SX corresponding to the sound source SX is supplied to the speaker arranged at the position of the sound source SL through a filter that realizes the transfer function portion of the equation (1), and the signal SX is supplied to the transfer function portion of the equation (2). Is supplied to the speaker arranged at the position of the sound source SR through a filter that realizes the above, the sound image by the audio signal SX can be localized at the position of the sound source SX.
[0018]
Therefore, the digital processing circuit 3 includes, for example, digital filters 31L to 34L and 31R to 34R and addition circuits 35L and 35R as shown in FIG. In this case, each digital filter can be configured as an FIR type by a delay circuit, a coefficient circuit, and an adder circuit, for example, as shown in FIG. 4A. Further, for example, the filters 31L and 31R can share a delay circuit as shown in FIG. 4B.
[0019]
The audio signals SLF to SRB from the A / D converter circuits 2A to 2D are supplied to the adding circuit 35L through the digital filters 31L to 34L, and are supplied to the adding circuit 35R through the digital filters 31R to 34R.
[0020]
At this time, the transfer functions of the digital filters 31L to 34L and 31R to 34R are set to predetermined values in accordance with the above-mentioned idea, and the transfer functions of the expressions (1) and (2) are set for the audio signals SLF to SRB. The impulse response obtained by converting the transfer function similar to the part into the time axis is convoluted.
[0021]
Therefore, an audio signal SL3 is output from the adder circuit 35L, and an audio signal SR3 is output from the adder circuit 35R. That is, the adder circuits 35L and 35R extract audio signals SL3 and SR3 that can reproduce the reproduction sound field when the four-channel audio signals SLF to SRB are reproduced by the four speakers.
[0022]
Next, the case where the digital processing circuit 4 is constituted by a discrete circuit will be described.
[0023]
As shown in FIG. 5, when the sound source SM is arranged in front of the listener LSNR,
HML: Transfer function from sound source SM to left ear of listener LSNR HMR: 右 Right ear 〃
Then, the digital processing circuit 4 has only to realize these transfer functions HML and HMR.
[0024]
Therefore, the digital processing circuit 4 includes, for example, digital filters 41L, 42L, 41R, and 42R and addition circuits 43L and 43R as shown in FIG. The digital filters 41L to 42R can be configured as shown in FIG. 4, for example, similarly to the digital filters 31L to 34R.
[0025]
The audio signals SL3 and SR3 from the digital processing circuit 3 are supplied to the adder circuit 43L through the digital filters 41L and 42L, and are supplied to the adder circuit 43R through the digital filters 41R and 42R. At this time, the transfer functions of the digital filters 41L to 42R are set to predetermined values, and the impulse responses obtained by converting the transfer functions to the time axis are convoluted with respect to the audio signals SL3 and SR3.
[0026]
Therefore, the audio signal SL4 is output from the adder circuit 43L, and the audio signal SR4 is output from the adder circuit 43R. That is, the adder circuits 43L and 43R extract audio signals SL4 and SR4 that can reproduce the reproduced sound field by the headphones 7 when the audio signals SL3 and SR3 are reproduced by the speaker.
[0027]
In this way, the digital processing circuit 3 converts the 4-channel audio signals SLF to SRB into audio signals SL3 and SR3 that can obtain a reproduction sound field equivalent to that of the four speakers even with two speakers, and these signals SL3 and SR3. However, the digital processing circuit 4 converts the audio signals SL4 and SR4 to obtain a reproduced sound field equivalent to that of a speaker even with headphones. Therefore, when the audio signals SL4 and SR4 are supplied to the headphones 7, a reproduction sound field equivalent to the case of four speakers is reproduced.
[0028]
As described above, according to the audio reproduction device 10 described above, a four-channel reproduction sound field that is originally reproduced by four speakers can be reproduced by the headphones 7. In this case, generally, digital processing is performed. Since the signal processing amount for reducing the number of channels by the circuit 3 can be made smaller than the signal processing amount for realizing the reproduction sound field of the speaker by the headphones by the digital processing circuit 4, according to the above-described audio apparatus. Compared with the case where all processes are performed together, the circuit scale can be reduced and the cost can be reduced.
[0029]
FIG. 7 shows a case where not only the headphones 7 but also speakers can be used. That is, the audio signal lines from the input terminals 11 to 14 to the headphones 7 are configured as described above, and the audio signals SL3 and SR3 from the digital processing circuit 3 are supplied to the D / A converter circuits 50L and 50R to be analog. The audio signals SL3 and SR3 are D / A converted, and these audio signals SL3 and SR3 are supplied to the speakers 70L and 70R through the power amplifiers 60L and 60R. The speakers 70L and 70R are disposed on the left front and right front of the listener.
[0030]
Therefore, the reproduced sound field equivalent to that of the four speakers can be obtained by the headphones 7, and the reproduced sound field equivalent to that of the four speakers can be obtained by the speakers 70L and 70R.
[0031]
In addition, in that case, the digital processing circuit 3 and the like can be used in common, and there is no need to switch the characteristics of the digital processing circuit 3 between reproduction by the headphones 7 and reproduction by the speakers 70L and 70R. For example, when the digital processing circuit 3 is configured by a DSP, it is not necessary to change the processing contents and parameters.
[0032]
FIG. 8 shows a case where the audio playback apparatus 10 can be connected to a signal source of a multi-channel digital audio signal. That is, in FIG. 8, reference numeral 100 denotes a digital audio signal source. In this example, the signal source 100 is a DVD player. From the DVD player 100, for example, a so-called 5.1 channel digital audio signal SDA in Dolby Digital (AC3) is extracted.
[0033]
This digital audio signal SDA is composed of 6 channels of digital audio signals SLF, SCF, SRF, SLB, SRB, and SLOW in one serial front, left front, center front, right front, left rear, right rear and 120Hz or lower. It is a signal encoded in data. In general, the signal SDA is decoded and D / A converted into the original 6-channel audio signals SLF to SLOW supplied to the dedicated adapter, and the signals SLF to SLOW are supplied to the respective speakers for reproduction. A sound field is formed.
[0034]
Then, such a signal SDA is supplied from the player 100 to the decoder circuit 2 of the audio reproducing apparatus 10 through the coaxial cable 101, and is decoded or separated into respective audio signals SLF to SLOW, and these audio signals SLF to SLOW are digitally processed. Reproduction obtained when these signals SLF to SLOW are supplied to the circuit 3 and are supplied to speakers arranged at the left front, center front, right front, left rear and right rear of the listener, respectively. A reproduced sound field equivalent to the sound field is converted into two-channel audio signals SL3 and SR3 reproduced by two speakers.
[0035]
The audio signals SL3 and SR3 are supplied to the digital processing circuit 4 and converted into headphone audio signals SL4 and SR4, and then supplied to the headphones 7 through the D / A converter circuits 5L and 5R and the amplifiers 6L and 6R. The
[0036]
Therefore, according to the audio device 10, a reproduced sound field equivalent to the reproduced sound field obtained when the six-channel audio signals SLF to SLOW are supplied to the six speakers can be reproduced by the headphones 7.
[0037]
In this case, the connection between the DVD player 1 and the audio playback device 10 is only one cable 101, and the connection is simple. Further, since the digital audio signal SDA reproduced by the DVD player 100 is supplied to the audio reproducing apparatus 10 as it is without being D / A converted into an analog audio signal, sound field reproduction is realized, so that deterioration of sound quality is avoided. can do.
[0038]
In the audio playback apparatus 10 as well, as in the audio playback apparatus of FIG. 7, the audio signals SL3 and SR3 output from the digital processing circuit 3 are subjected to D / A conversion and power amplification, and then the left front and right front of the listener. If the two speakers are supplied, the reproduction sound field equivalent to the reproduction sound field by the six speakers can be realized by two speakers.
[0039]
By the way, as shown in FIG. 9, for example, when the sound sources SL and SR are arranged at the left front and right front of the listener LSNR and the sound image is localized at an arbitrary position outside the head, the listener LSNR changes the head direction. According to the direction, the transfer functions HLL, HLR, HRL, and HRR change. This change in the transfer functions HLL to HRR is a factor for the listener LSNR to recognize the position of the sound image, and reproducing the change is known to contribute to the improvement in the quality of localization of the sound image. Yes.
[0040]
However, in the audio reproduction device 10 described above, the transfer function is constant regardless of the direction of the listener's head. Therefore, when headphone playback is performed by the audio playback device 10 described above, the sound image is localized at a certain position as viewed from the listener, regardless of the orientation of the listener's head.
[0041]
Therefore, for example, when listening to orchestra music, changing the head orientation makes it feel as if the entire orchestra has moved following the listener's head orientation. Alternatively, in the case of the audio playback device 10 described with reference to FIG. 8, the video played back by the DVD player 100 is displayed at an absolute position on the display regardless of the head direction of the listener. On the other hand, since the sound image moves together when the listener changes the direction of the head, a shift occurs between the position of the image and the position of the sound image.
[0042]
Therefore, FIG. 10 shows a case where the sound image remains localized at the original position even when the listener changes the direction of the head.
[0043]
That is, the audio signal lines from the DVD player 100 to the headphones 7 are configured as described in FIG. Further, when the headphone 7 is provided with a rotation angle sensor 81 and the headphone 7 is attached to the listener, the rotation angular velocity of the head of the listener is detected, and the detection signal S81 is passed through the bandpass filter 82 to the A / D converter circuit 83. And A / D converted into a digital detection signal S 81, and the detection signal S 81 is supplied to the microcomputer 84.
[0044]
Then, in the microcomputer 84, the detection signal S81 is sampled every predetermined time and then integrated to be converted into angle data indicating the head direction of the listener. Then, an angle for actually localizing the sound image is calculated from the angle data, and predetermined data is created. The transfer function in the digital processing circuit 4 is changed by this data, and even if the listener changes the head direction, The transfer function is controlled so that the absolute position of the sound image does not change.
[0045]
Therefore, when the listener changes the direction of the head, the transfer function in the digital processing circuit 4 changes in accordance with the direction of the head, so that the sound image formed by the headphones 7 is located at a fixed place in the outside world regardless of the direction of the head. It will be localized. Therefore, for example, when listening to orchestra music, even if the head direction is changed, the orchestra does not move, and a natural state is obtained in which the head direction is changed in front of the orchestra. Alternatively, when reproduction is performed by the DVD player 100, the localization position of the sound image can be made to coincide with the position of the video image even if the head direction is changed.
[0046]
By the way, the digital processing circuit 4 can be configured as shown in FIG. 11, for example. That is, the audio signals SL3 and SR3 from the digital processing circuit 3 are added at a predetermined ratio in the adding circuit 44L and supplied to the digital filter 41, and the audio signals SL3 and SR3 are added to the predetermined signal in the subtracting circuit 44R. The data is subtracted and supplied to the digital filter 42.
[0047]
The output signals of the digital filters 41 and 42 are subtracted at a predetermined ratio in the subtraction circuit 45L to extract the digital audio signal SL4, and the output signals of the filters 41 and 42 are subtracted at a predetermined ratio in the addition circuit 45R. And the digital audio signal SR4 is extracted.
[0048]
In this way, the data processing amount of the digital processing circuit 4 can be reduced, which is particularly advantageous when the digital processing circuit 4 is configured by a DSP.
[0049]
Furthermore, the digital processing circuit 4 of the audio reproduction device 10 of FIG. 10 can also be configured as shown below.
[0050]
That is, for example, in FIG. 9, when the listener LSNR turns his head to the right, the left ear approaches the sound source SL, and the right ear is far from the sound source SL, so out of the sound waves from the left front sound source SL, The sound wave that arrives reaches earlier than the sound wave that reaches the right ear. Further, the level of the sound wave reaching the left ear is higher than the level of the sound wave reaching the right ear.
[0051]
Therefore, a dynamic transfer function can be simulated by controlling a change with respect to the reference direction (a change in sound wave arrival time and level) with a microcomputer.
[0052]
Therefore, the digital processing circuit 4 shown in FIG. 12 is simplified in view of such points, and the digital filters 41L to 42R and the addition circuits 43L and 43R are configured in the same manner as in FIG. At the same time, the output signals SL4 and SR4 of the adder circuits 43L and 43R are taken out through the time delay adding variable delay circuits 46L and 46R and further through the level difference adding level control circuits 47L and 47R.
[0053]
In this case, the variable delay circuits 46L and 46R and the level control circuits 47L and 47R realize the change of the transfer function due to the movement of the listener's head as described above by the time difference and the level difference of the sound waves that reach both ears. is there. Therefore, the delay time of the variable delay circuits 46L and 46R and the attenuation amount of the level control circuits 47L and 47R are controlled by the control signal from the microcomputer 84 in accordance with the head direction of the listener.
[0054]
FIG. 13 shows control characteristics of the time difference between the signals SL4 and SR4 by the variable delay circuits 46L and 46R. The horizontal axis is, for example, an isosceles triangle whose base is a straight line connecting the sound source SL and the sound source SR in FIG. When the listener LSNR is located at the apex of the head, the front direction is θ = 0 °. Further, θ> 0 is set when the head is directed rightward, and θ <0 is set when the head is directed leftward.
[0055]
The broken lines TL and TR indicate the characteristics of the delay time added to the audio signals SL4 and S4R by the variable delay circuits 46L and 46R. These characteristics TL and TR are opposite to the rotation direction of the head of the listener LSNR. It changes in the direction and is targeted around θ = 0 (front).
[0056]
Further, FIG. 14 shows the control characteristics of the level difference between the signals SL4 and SR4 by the level control circuits 47L and 47R. The curves AL and AR are added to the audio signals SL4 and S4R by the level control circuits 47L and 47R. Indicates the level characteristics. These characteristics AL and AR change in the opposite direction to the rotation direction of the head of the listener LSNR, and are the target characteristics centering on θ = 0 °.
[0057]
When these characteristics TL, TR, AL, and AR are given to the audio signals SL4 and SR4, the sound from the sound source arranged in front of the listener LSNR is reproduced even if the reproduced sound is from the headphones 7. That is, the same time change and level change as when listening with the state changed. Therefore, even if the listener LSNR changes the head orientation, the sound image remains localized at the original position.
[0058]
In the above description, the rotation angle sensor 81 for detecting the head direction of the listener LSNR can be a piezoelectric vibration gyro or a geomagnetic direction sensor. Alternatively, the light emitting means may be arranged in front of or around the listener LSNR, and at least two light intensity sensors may be provided in the headphone 7, and the rotation angle of the head of the listener LSNR can be calculated from the output ratio of these light intensity sensors. .
[0059]
In addition, the ultrasonic sensors provided at two distant locations on the headphone 7 receive burst ultrasonic waves output from an ultrasonic oscillator in front of or around the listener LSNR, and convert them into received signals. The rotation angle of the headphones 7 can also be calculated from the time difference between the received signals. Furthermore, part or all of the rotation angle sensor 81 and the circuits 82 to 84 can be provided in the headphones 7. Also, the audio signals SL4 and SR4 can be supplied to the headphones 7 wirelessly using FM waves or infrared rays. Similarly, the audio signals SLF to SRB or the signal SDA can be supplied to the reproduction apparatus 10 wirelessly.
[0060]
【The invention's effect】
According to the present invention, it is possible to realize a reproduction sound field equivalent to that obtained when audio reproduction is performed by supplying a multi-channel audio signal to a large number of speakers using headphones. In addition, the circuit scale can be reduced and the cost can be reduced as compared with the case where all the processes are performed together.
[0061]
Furthermore, a reproduction sound field equivalent to the sound field of multi-channel reproduction can be obtained by both headphones and speakers. In addition, in that case, a signal processing circuit or the like can be used in common, and there is no need to switch the characteristics of the signal processing circuit between reproduction using headphones and reproduction using a speaker.
[0062]
In addition, the connection with a digital audio signal source such as a DVD player can be made with a single cable, and the connection is simple and the digital audio signal from the signal source can be supplied as it is, resulting in deterioration in sound quality. Can be avoided.
[0063]
Furthermore, even if the listener changes the head direction, the localization position of the sound image formed by the headphones can be matched with the position of the video.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of the present invention.
FIG. 2 is a plan view for explaining the present invention.
FIG. 3 is a system diagram showing an embodiment of a circuit that can be used in the present invention.
FIG. 4 is a system diagram showing an embodiment of a circuit that can be used in the present invention.
FIG. 5 is a plan view for explaining the present invention.
FIG. 6 is a system diagram showing an embodiment of a circuit that can be used in the present invention.
FIG. 7 is a system diagram showing another embodiment of the present invention.
FIG. 8 is a system diagram showing another embodiment of the present invention.
FIG. 9 is a plan view for explaining the present invention.
FIG. 10 is a system diagram showing another embodiment of the present invention.
FIG. 11 is a system diagram showing an embodiment of a circuit that can be used in the present invention.
FIG. 12 is a system diagram showing an embodiment of a circuit that can be used in the present invention.
FIG. 13 is a characteristic diagram for explaining the present invention.
FIG. 14 is a characteristic diagram for explaining the present invention.
[Explanation of symbols]
3 = digital processing circuit, 4 = digital processing circuit, 5L and 5R = D / A converter circuit, 7 = headphone, 10 = audio reproduction device, 11-14 = input terminal, 21-24 = A / D converter circuit

Claims (5)

The input audio signal is a four-channel audio signal supplied to each speaker arranged at the left front, right front, left rear, and right rear of the listener, and a predetermined reproduction sound field is generated by the reproduction sound of the speaker. When the audio signal to be formed,
A first signal processing circuit for converting the input audio signal into a two-channel audio signal according to a first transfer function;
A second signal processing circuit for converting the two-channel audio signal output from the first signal processing circuit according to a second transfer function;
A terminal for outputting the two-channel audio signal output from the first signal processing circuit to the outside ;
When the two-channel audio signals output from the first signal processing circuit are supplied to two speakers arranged at the left front and right front of the listener, the first signal processing circuit The input audio signal is converted into the two-channel audio signal so that a reproduction sound field equivalent to the field is formed,
The second signal processing circuit has a reproduction sound field obtained when the two-channel audio signal is supplied to the two speakers when the output audio signal of the second signal processing circuit is supplied to the headphones. The two-channel audio signal is converted into the output audio signal so that a reproduction sound field equivalent to the above is formed,
An audio reproducing apparatus, wherein an output audio signal of the second signal processing circuit is supplied to the headphones to obtain a reproduction sound field by the 4- channel audio signal. 6 channels to which the input audio signal is supplied to each of the speakers arranged at the left front, center front, right front, left rear or side of the listener, and the right rear or side of the listener, and a speaker for bass. Audio signal that forms a predetermined reproduction sound field by the reproduction sound of the speaker,
A first signal processing circuit for converting the input audio signal into a two-channel audio signal according to a first transfer function;
A second signal processing circuit for converting the two-channel audio signal output from the first signal processing circuit according to a second transfer function;
A terminal for outputting the two-channel audio signal output from the first signal processing circuit to the outside ;
When the two-channel audio signals output from the first signal processing circuit are supplied to two speakers arranged at the left front and right front of the listener, the first signal processing circuit The input audio signal is converted into the two-channel audio signal so that a reproduction sound field equivalent to the field is formed,
The second signal processing circuit has a reproduction sound field obtained when the two-channel audio signal is supplied to the two speakers when the output audio signal of the second signal processing circuit is supplied to the headphones. The two-channel audio signal is converted into the output audio signal so that a reproduction sound field equivalent to the above is formed,
An audio reproducing apparatus, wherein an output audio signal of the second signal processing circuit is supplied to the headphones to obtain a reproduction sound field by the 6-channel audio signal. The audio playback device according to claim 2 , wherein
When the 6-channel audio signal is encoded into a 1-channel audio signal,
A decoder circuit for decoding the 1-channel audio signal into the 6-channel audio signal;
An audio reproduction apparatus in which the 6-channel audio signal from the decoder circuit is supplied to the first signal processing circuit as the input audio signal . The audio playback device according to claim 1, 2 or 3 ,
Detecting means for detecting the orientation of the listener's head;
An audio reproducing apparatus for correcting a transfer function in the second signal processing circuit in accordance with a detection output of the detecting means . The audio playback device according to claim 4 , wherein
An audio reproducing apparatus in which the output audio signal is wirelessly supplied to the headphones .

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