JP3994296B2 - Audio playback device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an audio playback device.
[0002]
[Prior art]
In general, an audio signal accompanying a video such as a movie is recorded on the assumption that it is reproduced by speakers placed on both sides of the screen. According to this, the position of the sound source in the video matches the position of the sound image that can actually be heard, and a sound field having a more natural spread is established.
[0003]
However, when such an audio signal is viewed using headphones, the sound image is localized in the head, and the direction of the image does not match the localization of the sound image, resulting in a very unnatural sound image localization. .
[0004]
The same applies to the case of listening to music or the like that does not involve video, and unlike the case of speaker playback, the sound can be heard from within the head, resulting in an unnatural playback sound field.
[0005]
Therefore, the head-related transfer function (impulse response) from the speaker placed in front of the listener to the listener's ears is measured or calculated in advance, and this is convolved with the audio signal by a digital filter such as an FIR filter, and the resulting audio A method of supplying a signal to headphones is considered. According to this method, the sound image is localized outside the head, and a sound field close to that in the case of speaker reproduction can be reproduced.
[0006]
However, according to this method, the sound image is localized outside the head, but when the head is changed, the sound image moves together with the movement of the head. Deviation occurs in the direction of the sound image, resulting in an unnatural sound image localization.
[0007]
In view of this, a method of detecting the head movement, updating the coefficient of the digital fill according to the head movement, and fixing the direction of the sound image with respect to the listening environment has been considered. According to this method, the sound image is not localized in the head, and even if the head is moved, the sound image does not move, so that a sound image very similar to the sound image reproduced by the speaker can be obtained.
[0008]
However, when updating the coefficient of the digital filter according to the movement of the head, if the head moves even a little, the coefficient of the digital filter must be updated each time, and a large number of product-sum operation circuits are high-speed. And memory.
[0009]
Therefore, the coefficient of the digital filter is fixed to the value when the head is facing the front, for example, and the change of the coefficient with respect to the movement of the head is substituted or simulated by changing the time difference and the level difference with respect to the audio signal of each channel. A way to do this is considered. According to this method, it is not necessary to sequentially update the coefficients of the digital filter, and the circuit scale can be greatly simplified.
[0010]
However, in this method, the direction of sound image localization that can be realized by the time difference and the level difference is limited to the range of 180 ° forward, and the sound image cannot be localized backward.
[0011]
Further, when the position of the sound image is fixed, a new problem occurs. That is, for example, when there is a sound source in front, if the user turns to the right, the left ear approaches the sound source, so that the time delay of the sound wave incident on the left ear is reduced and the level is increased. However, when there is a sound source behind, if the user turns to the right, the left ear moves away from the sound source, so the time delay of the sound wave incident on the left ear increases and the level decreases.
[0012]
Therefore, when updating the coefficient of the digital filter according to the movement of the head, the direction of change of the coefficient must be reversed depending on the position of the sound source. If the coefficient is simply updated, the sound image is localized at the intended position. I ca n’t keep it.
[0013]
[Problems to be solved by the invention]
As described above, various methods have been considered as methods for reproducing the speaker sound field using headphones, but each has its own problems.
[0014]
Furthermore, according to experiments, there are cases where the expression of the sound field is richer if some of the sound images are localized in the head rather than being localized outside the head. This is because the localization in the head cannot be easily realized by speaker reproduction. For example, when the video is a scene with a bow, if the last sound is reproduced at the listener's ear, the effect cannot be expressed by speaker reproduction.
[0015]
In addition, there is a need to be able to cope with more input signals such as a multi-channel digital input signal such as AC-3.
[0016]
The present invention has been made in view of the above circumstances, and when reproducing a speaker sound field using headphones, it is intended to realize front and rear sound image localization while suppressing the amount of calculation of impulse response bonuses. It is.
[0017]
In addition, it uses the phenomenon of localization in the head effectively to increase the expressive power of the sound field. Alternatively, it is intended to realize a surround sound field with only a vague sense of direction.
[0018]
Furthermore, it is possible to cope with a larger number of input signals such as a multi-channel digital input signal such as AC-3.
[0019]
[Means for Solving the Problems]
  For this reason,thisIn the invention,
  A signal processing circuit for performing predetermined signal processing on input audio signals of a plurality of N channels (N = U + V + W);
  A headphone to which the output signal of this signal processing circuit is supplied;
  Detecting means provided on the headphone for detecting the orientation of the head of the headphone wearer;
  A circuit for processing the detection output of the detection means and outputting predetermined control data;
Have
  The signal processing circuit is
    2 U digital filters that convolve an impulse response obtained by converting a head-related transfer function from the U sound sources located in front of the N-channel audio signals to the left and right ears of the wearer into the time domain;
    2V digital filters that convolve impulse responses obtained by converting head-related transfer functions from the V sound sources located behind to the left and right ears into the time domain out of the N-channel audio signals;
    Of the N channel input audio signals,Excluding U sound sources located in front and V sound sources located in rear2W digital filters that convolve impulse responses obtained by transforming the head-related transfer functions from the W sound sources to the left and right ears into the time domain;
    A first pair of addition circuits for adding the outputs of the digital filters respectively corresponding to the front left and right channels out of the 2U digital filters;
    A second pair of addition circuits for adding the outputs of the digital filters respectively corresponding to the rear left and right channels out of the 2V digital filters;
    A third pair of adder circuits for adding the outputs of the digital filters respectively corresponding to the left and right channels out of the 2W digital filters;
    A first pair of additional circuits that respectively add a time difference and a level difference to the outputs of the first pair of adder circuits;
    A second pair of additional circuits for adding a time difference and a level difference to the outputs of the second pair of adder circuits,
    A third pair of additional circuits for adding a time difference and a level difference to the outputs of the third pair of adder circuits,
  A fourth pair of adder circuits that add the outputs of the first, second, and third pair of additional circuits to the left and right channel output signals of the signal processing circuit;
  Have
  When the orientation of the wearer's head changes, the first pair of additional circuits and the second pair of additional circuits cause a time difference and a level difference in opposite directions to the signals passing through them. The time difference and level difference are controlled by the control data as givenWith
Even when the orientation of the head of the wearer changes, the time difference and level difference added by the third pair of additional circuits are kept constant.
  Audio playback device
It is what.
  Therefore, even if the listener changes the direction of the head, the front and rear sound images are localized at that position.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
  FIG. 1 shows the present invention.Is the premise of1 shows an entire form of an audio reproducing apparatus. The codes SLF, SRF, SLB, and SRB are 4-channel analog audio signals. These signals SLF, SRF, SLB, and SRB are, for example, as shown in FIG. When supplied to the speakers SPLF, SPRF, SPLB, and SPRB arranged at the rear and right rear, a four-channel stereo reproduction sound field is realized.
[0021]
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 audio signals SLF to SRB after the A / D conversion are, for example, It is supplied to a digital processing circuit 3 constituted by a DSP.
[0022]
Although details of the digital processing circuit 3 will be described later, this converts the audio signals SLF to SRB into audio signals SL and SR that reproduce a predetermined stereo reproduction sound field by headphones.
[0023]
The audio signals SL and SR are supplied to the D / A converter circuits 4L and 4R and D / A converted. The analog audio signals SL and SR after the D / A conversion are supplied to the headphones 6 through the headphone amplifiers 5L and 5R. Left and right acoustic units (electric / acoustic transducers) 6L and 6R.
[0024]
Further, a rotational angular velocity sensor 71 is provided in the headphone 6 and its output signal is supplied to the detection circuit 72 to detect the angular velocity when the listener rotates the head with the headphone 6 attached thereto, and the detection signal S72. Is supplied to the A / D converter circuit 73 and A / D converted into a digital detection signal S 72, and the detection signal S 72 is supplied to the microcomputer 74.
[0025]
Then, in the microcomputer 74, the detection signal S72 is sampled every predetermined time and then integrated and converted into angle data indicating the head direction of the listener, and the sound image is actually localized from the data of this angle. Data S74 is created for this purpose, and this data S74 is supplied to the digital processing circuit 3 as a control signal.
[0026]
Next, the case where the digital processing circuit 3 is constituted by a discrete circuit will be described.
[0027]
Now, as shown in FIG. 3, when the speakers SPLF, SPRF, SPLB, SPRB are arranged at the left front, right front, left rear, and right rear of the listener M,
HLF-L: Head-related transfer function from speaker SPLF to listener M's left ear
HLF-R: Head-related transfer function from speaker SPLF to listener M's right ear
HRF-L: Head-related transfer function from speaker SPRF to the left ear of listener M
...
HRB-R: Head-related transfer function from speaker SPRB to the right ear of listener M
Then, the digital processing circuit 3 only needs to realize these head related transfer functions HLF-L to HRB-R.
[0028]
Therefore, the digital processing circuit 3 is configured as shown in FIG. 2, for example. The digital processing circuit 3 includes a processing circuit 3F that processes the signals SLF and SRF of the front channel among the audio signals SLF to SRB, and a processing circuit 3B that processes the signals SLB and SRB of the rear channel.
[0029]
That is, in the processing circuit 3F for the front channel, the audio signals SLF and SRF from the A / D converter circuits 21 and 22 are supplied to the adding circuit 321 through the digital filters 311 and 3120, and the added signal is added to the time difference adding circuit. 331 and the level difference adding circuit 341 are supplied to the adding circuit 35L. Also, the audio signals SLF and SRF from the A / D converter circuits 21 and 22 are supplied to the adding circuit 322 through the digital filters 3110 and 312, and the added signals are supplied through the time difference adding circuit 332 and the level difference adding circuit 342. It is supplied to the adding circuit 35R.
[0030]
Further, in the rear channel processing circuit 3B, the audio signals SLB and SRB from the A / D converter circuits 23 and 24 are supplied to the adding circuit 323 through the digital filters 313 and 3140, and the added signal is added to the time difference adding circuit. 333 and the level difference adding circuit 343 are supplied to the adding circuit 35R. Also, the audio signals SLB and SRB from the A / D converter circuits 23 and 24 are supplied to the adder circuit 324 through the digital filters 3130 and 314, and the added signal passes through the time difference adding circuit 334 and the level difference adding circuit 344. It is supplied to the adding circuit 35R.
[0031]
Then, the output signals of the adder circuits 35L and 35R are supplied to the D / A converter circuits 4L and 4R in the subsequent stage as audio signals SL and SR.
[0032]
In this case, the digital filters 311 to 314 and 3110 to 3140 are configured by, for example, FIR filters. These filters 311 to 314 and 3110 to 3140 correspond to the head-related transfer functions HLF-L to HRB-R and HLF-R to HRB-L when the listener M faces the front front in FIG. The head-related transfer function is set, and the impulse response obtained by converting the head-related transfer function into the time axis is convoluted with the audio signal passing through the filter.
[0033]
  Further, the addition circuits 331 to 334 add a predetermined time difference between the four audio signals passing through them, and are constituted by, for example, a delay circuit. Further, the addition circuits 341 to 344 add a predetermined level difference between the four audio signals passing through them, and are constituted by, for example, a variable gain amplifier. The additional circuits 331 to 334 are then used in accordance with the data S74 from the microcomputer 74.ofWhile the time difference is controlled, the level difference of the additional circuits 341 to 344 is controlled.
[0034]
In this case, when there is a sound source in front of the listener and the listener turns to the right, for example, the listener's left ear approaches the sound source, the time delay of the sound wave incident on the left ear is reduced and the level is increased. Conversely, when turning to the left, the time delay increases and the level decreases. Therefore, the characteristic of the additional circuit 331 is controlled as indicated by the broken line B in FIG. 4, and the characteristic of the additional circuit 341 is controlled as indicated by the curve C in FIG.
[0035]
Further, since the left ear and the right ear are in opposite positions, the characteristic of the additional circuit 332 is controlled as indicated by a broken line A in FIG. 4, and the characteristic of the additional circuit 342 is indicated by a curve D in FIG. Be controlled.
[0036]
On the other hand, when there is a sound source behind the listener and the listener turns to the right, for example, the listener's left ear moves away from the sound source, so the time delay of the sound wave incident on the left ear increases and the level decreases. Conversely, when turning to the left, the time delay becomes smaller and the level becomes larger. Therefore, the characteristic of the additional circuit 333 is controlled as indicated by a broken line A in FIG. 4, and the characteristic of the additional circuit 343 is controlled as indicated by a curve D in FIG. Further, the characteristic of the additional circuit 334 is controlled as indicated by a broken line B in FIG. 4, and the characteristic of the additional circuit 344 is controlled as indicated by a curve C in FIG.
[0037]
According to such a configuration, the audio signals SLF to SRB are convolved with the impulse responses corresponding to the head-related transfer function shown in FIG. 3 by the filters 311 to 3140, and the resulting signals SL and SR are output from the headphones 6. Since the sound images are supplied to the left and right channel acoustic units 6L and 6R, the sound image is localized outside the head, and a stereo reproduction sound field equivalent to the case of speaker reproduction is reproduced.
[0038]
When the listener changes the direction of the head, the characteristics of the additional circuits 331 to 334 and 341 to 344 change as shown in FIGS. 4 and 5 corresponding to the direction of the head, so that the sound image formed by the headphones 6 is Regardless of the direction of the head, it will be located in a fixed place in the outside world.
[0039]
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 the video is reproduced by a DVD player or the like, the localization position of the sound image can be matched with the video position even if the head direction is changed.
[0040]
By the way, in AC-3 etc., as shown in FIG. 6, in addition to the left front, right front, left rear and right rear speakers SPLF, SPRF, SPLB and SPRB of the listener M, It is assumed that SPCF is also arranged for stereo reproduction.
[0041]
FIG. 7 shows a case where such stereo reproduction is reproduced by headphones. That is, the analog audio signals SLF, SRF, SLB, SRB are supplied to the A / D converter circuits 21-24 through the input terminals 11-14 and A / D converted, and the analog audio signal SCF of the front front channel is The signal is supplied to the A / D converter circuit 20 through the input terminal 10 and A / D converted. Then, the audio signals SLF to SRB, SCF after the A / D conversion are supplied to the digital processing circuit 3 constituted by, for example, a DSP.
[0042]
Although details of the digital processing circuit 3 will be described later, this converts the audio signals SLF to SCF into audio signals SL and SR for reproducing a predetermined stereo reproduction sound field by the headphones 6.
[0043]
The audio signals SL and SR are supplied to the D / A converter circuits 4L and 4R and D / A converted. The analog audio signals SL and SR after the D / A conversion are supplied to the headphones 6 through the headphone amplifiers 5L and 5R. To the left and right acoustic units 6L, 6R.
[0044]
The headphone 6 is provided with a rotational angular velocity sensor 71, and its output signal is supplied to a detection circuit 72, and a detection signal S 72 of the rotational angular velocity of the listener's head is taken out. This signal S 72 is sent to the A / D converter circuit 73. After being supplied and A / D converted into a digital detection signal S72, it is supplied to the microcomputer 74. In the microcomputer 74, the detection signal S72 is converted into predetermined data S74, and this data S74 is controlled by the digital processing circuit 3. Supplied as a signal.
[0045]
When the digital processing circuit 3 is configured by a discrete circuit, for example, it is configured as shown in FIG. That is, in the case of stereo reproduction as shown in FIG. 6, the sound image reproduced by the speaker SPCF at the center front can be reproduced by the left and right speakers SPLF and SPRF.
[0046]
Therefore, in the processing circuit 3 shown in FIG. 8, in the processing circuit 3F of the front channel, the digital audio signals SLF and SRF from the A / D converter circuits 21 and 22 are added to the digital filters 311 to 3120 through the addition circuits 36L and 36R. And the digital audio signal SCF from the A / D converter circuit 20 is supplied to the adder circuits 36L and 36R through the attenuation circuit 37 and distributed to the audio signals SLF and SRF. Note that the processing circuits 3B for the rear and rear channels from the filters 311 to 3120 are configured in the same manner as in FIG.
[0047]
Therefore, in this audio reproduction device, the 5-channel stereo speaker reproduction sound field shown in FIG.
[0048]
FIG. 9 shows a case where connection to a signal source of a multi-channel digital audio signal is enabled. That is, in FIG. 9, reference numeral 900 indicates a signal source of a digital audio signal, and in this example, the signal source 900 is a DVD player. From this DVD player 900, for example, a so-called 5.1-channel digital audio signal SDA in Dolby Digital (AC-3) is taken out.
[0049]
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.
[0050]
Then, such a signal SDA is supplied from the player 900 to the decoder circuit 8 of the audio reproducing device through the coaxial cable 901 and is decoded or separated into the respective audio signals SLF to SLOW, and these audio signals SLF to SLOW are converted into digital processing circuits. 3 is supplied.
[0051]
The processing circuit 3 is configured in the same manner as the processing circuit 3 of FIG. 8, and the front front channel signal SCF is distributed to the left front and right front channel signals SLF and SRF. Further, the low frequency signal SLOW is, for example, The signals SLF to SRB are distributed. Further, the subsequent stage from the processing circuit 3 and the means 71 to 74 are configured in the same manner as that of FIG.
[0052]
Therefore, according to this audio reproduction apparatus, the headphone 6 can reproduce the reproduction sound field equivalent to the reproduction sound field obtained when the six-channel audio signals SLF to SLOW are supplied to the six speakers.
[0053]
In this case, the connection between the DVD player 1 and the audio playback device is only one cable 901, and the connection is simple. Further, since the digital audio signal SDA reproduced by the DVD player 900 is not converted into an analog audio signal but supplied to the audio reproducing apparatus as it is to realize the sound field reproduction, the deterioration of the sound quality is avoided. be able to.
[0054]
  FIG.According to this inventionThis is a case where general multi-channel stereo reproduction can be realized with headphones. That is, in this playback apparatus, multi-channel analog audio signals are divided into U front channel signals SF1 to SFU, V rear channel signals SB1 to SBV, and other W signals SS1 to SSW. And classified. The signals SF1 to SFU are signals supplied to speakers arranged in a range of 180 ° in front of the listener, and the signals SB1 to SBV are supplied to speakers arranged in a range of 180 ° behind the listener. Signal. Further, the signals SS1 to SSW are signals that give a vague sense of direction and out-of-head localization.
[0055]
The front channel audio signals SF1 to SFU are supplied to the A / D converter circuits 2F1 to 2FU through the input terminals 1F1 to 1FU and A / D converted, and the rear channel audio signals SB1 to SBV are input terminals. The signals are supplied to the A / D converter circuits 2B1 to 2BV through 1B1 to 1BV and A / D converted. Also, the audio signals SS1 to SSW and the input terminals 1S1 to 1SW are supplied to the A / D converter circuits 2S1 to 2SW for A / D conversion.
[0056]
Then, the audio signals SF1 to SFU, SB1 to SBV, and SS1 to SSW after the A / D conversion are supplied to the digital processing circuit 3 constituted by, for example, a DSP.
[0057]
Although details of the digital processing circuit 3 will be described later, this converts the audio signals SF1 to SSW into audio signals SL and SR for reproducing a predetermined stereo reproduction sound field by the headphones 6.
[0058]
The audio signals SL and SR are supplied to the D / A converter circuits 4L and 4R and D / A converted. The analog audio signals SL and SR after the D / A conversion are supplied to the headphones 6 through the headphone amplifiers 5L and 5R. To the left and right acoustic units 6L, 6R.
[0059]
The headphone 6 is provided with a rotational angular velocity sensor 71, and its output signal is supplied to a detection circuit 72, and a detection signal S 72 of the rotational angular velocity of the listener's head is taken out. This signal S 72 is sent to the A / D converter circuit 73. After being supplied and A / D converted into a digital detection signal S72, it is supplied to the microcomputer 74. In the microcomputer 74, predetermined data S74 is generated from the detection signal S72, and this data S74 is controlled by the digital processing circuit 3. Supplied as a signal.
[0060]
When the digital processing circuit 3 is configured by a discrete circuit, for example, it is configured as shown in FIG. That is, in the front channel processing circuit 3F, the signals SF1 to SFU are supplied to the adder circuit 321 through the digital filters 3111 to 311U and to the adder circuit 322 through the digital filters 3121 to 312U.
[0061]
In this case, the filters 3111 to 312U are speakers to which audio signals SF1 to SFU are supplied in the same manner as the filters 311 to 3120 in FIG. 2 realize the head related transfer functions HLF-L to HRF-L in FIG. And the head-related transfer function between the listener's ears. The output signals of the adder circuits 321 and 322 are supplied to the adder circuits 35L and 35R through the time difference addition circuits 331 and 332 and the level difference addition circuits 341 and 342, respectively.
[0062]
Although the illustration is simplified for the sake of space, the rear channel processing circuit 3B is configured in the same manner as the front channel processing circuit 3F, and V sets of digital audio signals SB1 to SBV are supplied. Filters (3131, 3141) to (313V, 314V), output signal adding circuits 323, 324, time difference adding circuits 333, 334 and level difference adding circuits 343, 344 to which the output signals are supplied. The output signal is supplied to addition circuits 35L and 35R.
[0063]
Further, the processing circuit 3S is configured in the same manner as the processing circuit 3B, and W sets of digital filters (3151, 3161) to (315W, 316W) to which the digital audio signals SS1 to SSW are supplied, and their output signals Adder circuits 325 and 326, time difference adding circuits 335 and 336 to which the output signals are supplied, and level difference adding circuits 345 and 346, and the output signals are supplied to the adder circuits 35L and 35R.
[0064]
The control signal S74 from the microcomputer 74 is supplied as a control signal to the additional circuits 331, 332, 341, and 342 of the processing circuit 3F, and is also supplied to the additional circuits 333, 334, 343, and 344 of the processing circuit 3B. The additional circuits 331 to 342 and 333 to 344 are controlled in the same manner as the processing circuits 3F and 3B in FIG. Note that the time difference and level difference of the additional circuits 335, 336, 345, and 346 in the processing circuit 3S are fixed to values when the listener is facing the front, or the additional circuits 331, 332, 341, and It is controlled to change opposite to that of 342.
[0065]
According to such a configuration, it is possible to reproduce the same multi-channel stereo reproduction sound field as when the audio signals SF1 to SFU, SB1 to SBV, and SS1 to SSW are supplied to the speakers. In that case, the sound image formed by the audio signals SF1 to SFU and SB1 to SBV of the front channel and the rear channel does not move even if the listener moves his / her head.
[0066]
However, since the remaining audio signals SS1 to SSW are not subjected to variable control of time difference and level difference, or are controlled in reverse to the signals SF1 to SFU of the front channel, the sound image formed by the signals SS1 to SSW. When the listener moves his / her head, the listener moves together, or has a vague direction and out-of-head orientation, and an effect that cannot be reproduced by speaker playback can be obtained.
[0067]
In the above description, the additional circuit 341 to 344 reproduces the localization of the sound image when the head direction is changed by giving a level difference to the audio signal. For example, when the sound source is ahead, it turns to the right. Since the high frequency of the sound wave incident on the right ear is lowered, the additional circuits 341 to 344 are used as frequency characteristic control circuits to add the frequency characteristic when the head direction is changed, particularly the high frequency change. May be.
[0068]
Further, in the addition circuits 331 to 334, a phase difference can be added instead of the time difference. Alternatively, the addition circuits 331 to 334 can add a phase difference, and the addition circuits 341 to 344 can add a change in frequency characteristics.
[0069]
Furthermore, in the above description, the rotational angular velocity sensor 71 that detects the head direction of the listener M can be a piezoelectric vibration gyro or a geomagnetic orientation sensor. Alternatively, the light emitting means may be disposed in front of or around the listener M, and at least two light intensity sensors may be provided in the headphones 6, and the rotation angle of the head of the listener M may be calculated from the output ratio of these light intensity sensors. .
[0070]
In addition, by using ultrasonic sensors provided at two distant locations on the headphone 6, burst ultrasonic waves output from an ultrasonic oscillator in front of or around the listener M are received and converted into reception signals, The rotation angle of the headphones 6 can also be calculated from the time difference between the received signals.
[0071]
Furthermore, the rotation angle of the head can also be detected by controlling the amount of light incident on the optical sensor in accordance with the direction of the head of the listener M by interlocking the optical shutter with the magnetic needle. Alternatively, if a magnetic needle is provided on the input shaft of the rotary encoder, a signal indicating the rotation angle of the head can be obtained in a digital signal state, and the A / D converter circuit 73 can be omitted.
[0072]
The detection circuit 72 can be a circuit corresponding to the detection method of the rotation angular velocity sensor 71. Furthermore, some or all of the rotational angular velocity sensor 71 and the circuits 72 to 74 can be provided in the headphones 6. Further, the audio signals SL and SR can be supplied to the headphones 6 wirelessly using FM waves or infrared rays.
[0073]
【The invention's effect】
According to the present invention, it is possible to reproduce the same characteristics as when listening to the sound image in front of the listener and the sound image behind the listener while actually moving the head. Localization can be realized.
[0074]
Further, it is not necessary to perform digital signal processing in all channels, and out-of-head localization can be realized for a sound image by a multi-channel audio signal with a relatively small amount of signal processing.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of the present invention.
FIG. 2 is a system diagram showing an embodiment of a part of the present invention.
FIG. 3 is a plan view for explaining the present invention.
FIG. 4 is a characteristic diagram for explaining the present invention.
FIG. 5 is a characteristic diagram for explaining the present invention.
FIG. 6 is a plan view for explaining 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 a part of the present invention.
FIG. 9 is a system diagram showing another embodiment of the present invention.
FIG. 10 is a system diagram showing another embodiment of the present invention.
FIG. 11 is a system diagram showing another embodiment of a part of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 3 ... Digital processing circuit, 3B ... Back channel processing circuit, 3F ... Front channel processing circuit, 4L and 4R ... D / A converter circuit, 5L and 5R ... Amplifier, 6 ... Headphone, 6L and 6R ... Sound unit, 11 -14: input terminals, 21-24: A / D converter circuit, 71: rotational angular velocity sensor, 72: detection circuit, 73: A / D converter circuit, 74: microcomputer
311 to 314 and 3110 to 3140: digital filter, 321-324: addition circuit, 331-334: time difference addition circuit, 341-344: level difference addition circuit, 35L and 35R: addition circuit

Claims (1)

A signal processing circuit for performing predetermined signal processing on input audio signals of a plurality of N channels (N = U + V + W);
A headphone to which the output signal of this signal processing circuit is supplied;
Detecting means provided on the headphone for detecting the orientation of the head of the headphone wearer;
A circuit for processing the detection output of the detection means and outputting predetermined control data;
The signal processing circuit is
2 U digital filters that convolve an impulse response obtained by converting a head-related transfer function from the U sound sources located in front of the N-channel audio signals to the left and right ears of the wearer into the time domain;
2V digital filters that convolve impulse responses obtained by converting head-related transfer functions from the V sound sources located behind to the left and right ears into the time domain out of the N-channel audio signals;
Of the N-channel input audio signals, the head-related transfer functions from the W sound sources excluding the U sound sources located in the front and the V sound sources located in the rear to the left and right ears are expressed as time. 2W digital filters that convolve the impulse response converted into a region;
A first pair of addition circuits for adding the outputs of the digital filters respectively corresponding to the front left and right channels among the 2U digital filters,
A second pair of addition circuits for adding the outputs of the digital filters respectively corresponding to the rear left and right channels out of the 2V digital filters;
A third pair of adder circuits for adding the outputs of the digital filters respectively corresponding to the left and right channels out of the 2W digital filters;
A first pair of additional circuits that respectively add a time difference and a level difference to the outputs of the first pair of adder circuits;
A second pair of additional circuits for adding a time difference and a level difference to the outputs of the second pair of adder circuits,
A third pair of additional circuits for adding a time difference and a level difference to the outputs of the third pair of adder circuits,
A fourth pair of adder circuits which add the outputs of the first, second and third pairs of additional circuits to the left and right channel output signals of the signal processing circuit, respectively,
When the orientation of the wearer's head changes, the first pair of additional circuits and the second pair of additional circuits cause a time difference and a level difference in opposite directions to the signals passing through them. The time difference and the level difference are controlled by the control data as given ,
An audio reproducing apparatus for maintaining a constant time difference and level difference added by the third pair of additional circuits even when the orientation of the head of the wearer is changed .

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