JP4943098B2 - Sound reproduction system and sound reproduction method - Google Patents

Description

  The present invention relates to an audio reproduction system and an audio reproduction method for performing multichannel surround reproduction.

  Conventionally, this type of sound reproduction system is disclosed in Japanese Patent Laid-Open No. 5-91600 (see FIG. 1 of Patent Document 1).

  This conventional sound reproduction system has the basic configuration shown in FIG. 1A, and transmits two-channel left and right stereo signals (left channel voice signal Lin and right channel audio signal Rin) to the listener's left and right front. In addition to independently supplying to the front speakers FL and FR provided, a signal subtraction circuit generates a difference signal (Lin−Rin) from the audio signals Lin and Rin, and based on the difference signal (Lin−Rin). The surround circuit generates the surround signals SL and SR and independently supplies them to the rear speakers RL and RR provided at the left and right rear sides of the listener.

  According to the sound reproduction system having such a configuration, the surround signals SL and SR are artificially generated from the audio signals Lin and Rin recorded on the recording medium or the like in the two-channel stereo system, and the audio signals Lin and Rin and the surround signal SL are generated. By driving each speaker FL, FR, RL, and RR based on SR, a multi-channel surround sound field that provides a more realistic sensation is realized as compared with the case of simply performing 2-channel stereo reproduction. .

JP-A-5-91600

  By the way, when the conventional sound reproduction system is used as, for example, a car audio system provided in a passenger compartment of an automobile, there is generally a restriction of the passenger compartment, and therefore, as shown in FIG. Audio signals Lin and Rin are supplied to the front speakers FL and FR installed on both sides of the front seat from the built-in sound reproduction system, and the surround signals are supplied to the rear speakers RL and RR installed on both sides of the rear seat. SL and SR are supplied.

  However, since the front speakers FL and FR and the rear speakers RL and RR are offset from the seating position of each passenger (asymmetrical position), the left channel that reaches the left and right ears of each passenger The playback sound and the playback sound of the right channel are out of phase with each other, which may make each passenger unnatural and uncomfortable.

  For example, the right front speaker FR is closer to the driver seated on the right front seat (driver's seat) than the left front speaker FL, and therefore, the driver is released from the front speakers FL and FR. The interaural correlation function of the stereo playback sound that reaches the left and right ears has a negative value indicating a reverse phase, which may be unnatural and uncomfortable. Further, similarly, the rear speakers RL and RR are positioned closer to the right rear speaker RR than the left rear speaker RL with respect to the driver. In some cases, the interaural correlation function of the surround playback sound that reaches the ear has a negative value indicating a reverse phase, which is unnatural and uncomfortable.

  The present invention has been made in view of such conventional problems, and automatically adjusts the reproduced sounds emitted from the speakers that are offset with respect to the listener so that they are in phase with each other. An object of the present invention is to provide a sound reproduction system that realizes a multi-channel surround sound field.

According to the first aspect of the present invention, a surround signal is artificially generated from a stereo left-channel audio signal and a right-channel audio signal, and the left speaker is provided with each left speaker at the left and right offset positions. more each rear speaker provided in the offset position of the left and right channel audio signals and the right channel and the listener, a sound reproduction system to perform a multi-channel surround reproduction, reproduction emitted from the respective front speakers The phase corresponding to the time difference required for the reproduced sound emitted from each front speaker to reach the left and right ears of the listener in a frequency range when the interaural correlation function of the sound is a negative value, The left channel audio signal and the right channel audio signal are relatively phase-shifted and supplied to the front speakers. A phase adjusting means, to generate a first surround signal by subtracting a sound signal of the right channel from the audio signal of the left channel, the by subtracting the audio signal of the left channel from the audio signal of the right channel 2 a surround signal generation means for generating a surround signal, the first extracts a signal component of the surround signal and the second surround signal from said frequency range, the first extracted signal component from the surround signal left rear speaker And a filter means for supplying the signal component extracted from the second surround signal to the right rear speaker .

  A preferred embodiment of the present invention will be described with reference to FIGS. 2 (a), 2 (b), and 2 (c).

  2A is a block diagram showing the configuration of the sound reproduction system of the first embodiment, FIG. 2B is a block diagram showing the configuration of the sound reproduction system of the second embodiment, and FIG. ) Is an explanatory diagram for explaining functions of the sound reproduction systems of the first and second embodiments.

[First Embodiment]
The sound reproduction system 1 according to the first embodiment includes a phase adjuster 2, subtractors 3L and 3R, and bandpass filters 4L and 4R, as shown in FIG. Left and right channels for driving the speakers FL and FR by performing predetermined signal processing on the two-channel stereo audio signals (left channel and right channel audio signals) Lin and Rin supplied from Sound signals L and R, and surround sound signals SL and SR for driving the speakers FL and FR.

  Here, it is assumed that the speakers FL, FR, RL, RR are assumed to be provided at positions offset with respect to each listener in the interior of the automobile as shown in FIG. To do.

  The phase adjuster 2 has a substantially constant gain characteristic in the full band (the whole band of the audible frequency), and in the predetermined frequency band PBW of the full band, the phase adjuster 2 adjusts the phase between the audio signals Lin and Rin. It is formed by a phase shift circuit or the like that relatively shifts phase by π (180 °). Then, the phase-shifted audio signals L and R are independently supplied to the front speakers FL and FR.

  That is, the phase adjuster 2 shifts only the phase of the audio signal Lin by π, so that the phase is relatively phase-shifted between the audio signals Lin and Rin, or the phase of the audio signal Rin. Phase shift circuit that relatively phase shifts between both audio signals Lin and Rin by phase-shifting only π, or based on the relationship that the sum of phases φ1 and φ2 becomes phase π The phase of Lin is shifted by φ1 and the phase of the audio signal Rin is shifted by φ2, thereby forming a phase shifter that relatively shifts the phase between the audio signals Lin and Rin by π.

  The frequency band PBW described above is determined as follows. In other words, by the experiment or the like, the same audio signal is supplied to the left and right front speakers FL and FR provided at an offset position with respect to the driver seat or the passenger seat, and the listener seats in the driver seat or the passenger seat. The interaural correlation function is measured for the frequency of the reproduced sound reaching the left ear and the reproduced sound reaching the right ear. When the measurement is performed in this manner, the interaural correlation function becomes a negative value (a value close to -1) in the frequency range of about 200 Hz to about 500 Hz in the passenger compartment of the automobile, as shown in FIG. , Listeners feel uncomfortable. Further, the binaural correlation function has the above-mentioned negative value means that the reproduction sound emitted from the front speaker FL and reaching the listener's left ear and the reproduction sound emitted from the front speaker FR and reaching the listener's right ear are reproduced. It means that the time difference due to the propagation delay with sound substantially corresponds to the phase π.

  Therefore, in the sound reproduction system 1 used in the passenger compartment, in the frequency band PBW of about 200 Hz to about 500 Hz, the phase is adjusted by a phase shift circuit or the like that relatively shifts the phase between the audio signals Lin and Rin. A vessel 2 is formed.

  Next, the subtractor 3L generates a difference signal (Lin−Rin) by subtracting the right channel audio signal Rin from the left channel audio signal Lin and supplies the difference signal (Lin−Rin) to the bandpass filter 4L.

  The subtractor 3R generates a difference signal (Rin−Lin) by subtracting the left-channel audio signal Lin from the right-channel audio signal Rin, and supplies the difference signal (Rin−Lin) to the band-pass filter 4R.

  The band-pass filter 4L is formed of a band-pass filter having substantially the same pass bandwidth (about 200 Hz to about 500 Hz) BW as the frequency band PBW described above, and has passed through the pass bandwidth BW of the difference signal (Lin−Rin). The signal (that is, the signal extracted with the pass bandwidth BW) is supplied as the surround signal SL to the left rear speaker RL.

  Similarly, the bandpass filter 4R is formed of a bandpass filter having a passband width (about 200 Hz to about 500 Hz) BW that is substantially the same as the frequency band PBW, and has passed through the passband width BW of the difference signal (Rin−Lin). The signal is supplied as a surround signal SR to the right rear speaker RR.

  Next, the operation of the sound reproduction system 1 of this embodiment having such a configuration will be described.

  When the two-channel stereo audio signals Lin and Rin are output from the signal source, the phase adjuster 2 relatively shifts the phase between the audio signals Lin and Rin within the frequency band PBW by π. The phase-shifted signals are supplied to the front speakers FL and FR as a left channel audio signal L and a right channel audio signal R to be sounded.

  Here, the delay time τ1 required for the reproduced sound emitted from the front speaker FL to reach the listener's left ear and the reproduced sound emitted from the front speaker FR required to reach the listener's right ear. Since the time difference (τ1−τ2) with respect to the delay time τ2 substantially corresponds to the phase π, both of the two emitted from the front speakers FL and FR based on the above-mentioned audio signals L and R phase-shifted by π. Reproduced sounds reach the listener's left and right ears almost in phase with each other. For this reason, it is possible to reduce a sense of discomfort for the listener who listens to the reproduced sound from the front speakers FL and FR provided at the offset position with respect to the listener.

  Furthermore, since the surround signals SL and SR supplied from the bandpass filters 4L and 4R to the rear speakers RL and RR are generated from the difference signals (Lin−Rin) and (Rin−Lin), the phases are π (180). °) will shift. The delay time τ3 required for the reproduced sound emitted from the rear speaker RL to reach the listener's left ear and the delay required for the reproduced sound emitted from the rear speaker RR to reach the listener's right ear. The time difference (τ3−τ4) from the time τ4 substantially corresponds to the phase π. For this reason, both reproduced sounds emitted from the rear speakers RL and RR based on the surround signals SL and SR reach the left and right ears of the listener in substantially positive phase with each other. Therefore, it is possible to reduce a sense of discomfort for the listener who listens to the reproduced sound from the rear speakers RL and RR provided at the offset position with respect to the listener.

  Furthermore, each speaker FL, FR, RL, RR is offset from each passenger (listener) seated in the front seat and the rear seat with substantially the same positional relationship. For this reason, it is possible to provide a natural multi-channel surround sound field without causing the driver, the passenger sitting on the front seat, and the passenger sitting on the rear seat to feel uncomfortable.

  As described above, according to the sound reproduction system 1 of the present embodiment, the reproduced sounds from the front speakers FL and FR are substantially in phase with each other, and the reproduced sounds from the rear speakers RL and RR are also substantially in phase with each other. Therefore, a natural multi-channel surround sound field can be realized without causing a sense of incongruity.

  As described above, the phase adjuster 2 is formed of a phase shift circuit. However, a band pass filter, a high pass filter, and a low pass filter each having a predetermined phase characteristic are connected in parallel or in series as appropriate. By combining them, it is possible to realize a phase shift circuit having a filter bank structure that exhibits a substantially constant phase characteristic in the frequency band PBW described above.

  Alternatively, an APF (adaptive phase filter) may be used as the phase adjuster 2 to exhibit a substantially constant phase characteristic in the frequency band PBW described above.

  Further, it has been described that the passband width BW of the bandpass filters 4L and 4R is substantially the same as the frequency band PBW of the phase adjuster 2. However, the passband width BW only needs to include at least the frequency band PBW, and may be a passband width having a passband up to a higher frequency. That is, the pass band width BW of the band pass filters 4L and 4R may be a pass band width including the frequency band PBW of the phase adjuster 2 and a pass band up to a higher frequency. As described above, when the passband width BW of the bandpass filters 4L and 4R is expanded to a high frequency, a sense of depth in the vocal band can be increased, and a sense of sound image localization and a sense of sound spread can be improved.

  The sound reproduction system 1 of the present embodiment can be formed by an analog circuit when the audio signals Lin and Rin are supplied as analog signals, and the audio signals Lin and Rin are supplied as digital signals. In some cases, it can be formed by a digital circuit.

  Further, the sound reproduction system 1 may be realized by creating a computer program corresponding to the configuration of the digital circuit described above and causing the microprocessor (MPU) or digital signal processor (DSP) to execute the computer program.

[Second Embodiment]
Next, the sound reproduction system 1 of the second embodiment will be described with reference to FIGS. Note that, in FIG. 2B, the same or corresponding parts as those in FIG.

  The sound reproduction system 1 of this embodiment shown in FIG. 2B has a configuration in which adders 5L and 5R are further added to the sound reproduction system shown in FIG. Then, as shown in FIG. 2B, multi-channel surround reproduction is performed by driving the speakers FL, FR, RL, and RR provided in the passenger compartment of the automobile.

  Here, the adder 5L adds (synthesizes) the left channel audio signal L phase-adjusted by the phase adjuster 2 in the frequency band PBW and the surround audio signal SL that has passed through the bandpass filter 4L, and synthesizes them. The signal is supplied to the front speaker FL as a left channel audio signal Lout.

  The adder 5R adds (synthesizes) the right channel audio signal R phase-adjusted by the phase adjuster 2 and the surround audio signal SR passed through the bandpass filter 4R, and the synthesized signal is the right channel audio signal. Rout is supplied to the front speaker FR.

  According to the sound reproduction system 1 of the present embodiment having such a configuration, the same effects as those of the first embodiment described above can be obtained, and surround sound can be emitted from the front speakers FL and FR. A multi-channel surround sound field with a sense of realism can be realized.

  That is, from the front speaker FL to which the left channel audio signal Lout is supplied, the reproduction sound by the audio signal L and the reproduction sound by the surround audio signal SL are emitted, and from the front speaker FR to which the right channel audio signal Rout is supplied. The sound reproduced by the audio signal R and the sound reproduced by the surround sound signal SR are emitted. Since the sound reproduced by the audio signal L and the sound reproduced by the audio signal R are emitted with a phase shift of π corresponding to the time difference of the propagation delay, they are almost in phase with each other and reach the left and right ears of the listener. Furthermore, since the surround sound signals SL and SR are originally shifted from each other by the phase π, the reproduced sound by the surround sound signal SL and the reproduced sound by the surround sound signal SR are shifted from each other by the phase π corresponding to the time difference of the propagation delay. And reach the listener's left and right ears almost in phase with each other. Furthermore, reproduced sounds emitted from the rear speakers RL and RR by the surround sound signals SL and SR are also emitted while being shifted from each other by a phase π corresponding to a time difference in propagation delay, and become substantially in phase with each other. Reach the ears.

  In this way, the reproduced sound emitted from the front speakers FL and FR reaches the listener's left and right ears in almost normal phase, and the reproduced sound emitted from the rear speakers RL and RR is also left and right of the listener. Since it reaches the ear almost in phase, it is possible to realize a natural multi-channel surround sound field without giving a sense of incongruity, and it is also possible to emit surround sound from the front speakers FL and FR. Therefore, it is possible to realize a multi-channel surround sound field that provides a more realistic feeling.

  In the present embodiment described above, it has been described that the passband width BW of the bandpass filters 4L and 4R is substantially the same as the frequency band PBW of the phase adjuster 2. However, the passband width BW only needs to include at least the frequency band PBW, and may be a passband width having a passband up to a higher frequency. That is, the pass band width BW of the band pass filters 4L and 4R may be a pass band width including the frequency band PBW of the phase adjuster 2 and a pass band up to a higher frequency. As described above, when the passband width BW of the bandpass filters 4L and 4R is expanded to a high frequency, a sense of depth in the vocal band can be increased, and a sense of sound image localization can be further improved.

  In the configuration shown in FIG. 2B, the audio signals L and R and the surround audio signals SL and SR are added to the front speakers FL and FR by the adders 5L and 5R, respectively, and supplied to the rear speakers. Although only the surround sound signals SL and SR are supplied to the RL and RR, a configuration shown in FIG. 3 may be used as a modification of the present embodiment.

  That is, as shown in FIG. 3, the audio signals L and R and the surround audio signals SL and SR are added by the adders 5L and 5R and supplied to the front speakers FL and FR, respectively, and output from the phase adjuster 2. The audio signal L and the surround audio signal SL output from the band pass filter 4L are added by an adder 5SL, and the added signal SLout is supplied to the rear speaker RL of the left channel, and the audio output from the phase adjuster 2 The signal R and the surround sound signal SR output from the band pass filter 4R may be added by the adder 5SR, and the added signal SRout may be supplied to the right channel rear speaker RR.

  Also in the modified example of such a configuration, the reproduced sound emitted from the front speakers FL and FR reaches the listener's left and right ears in almost normal phase, and the reproduced sound emitted from the rear speakers RL and RR is also received. Since it reaches the right and left ears of the listener almost in phase, it is possible to realize a natural multi-channel surround sound field without giving a sense of incongruity. Furthermore, not only the main channel reproduction sound but also the surround reproduction sound can be emitted from the front speakers FL and FR, and the main channel reproduction sound as well as the surround reproduction sound can be emitted from the rear speakers RL and RR. Therefore, it is possible to realize a multi-channel surround sound field that provides a more realistic feeling.

  Further, the sound reproduction system 1 of the present embodiment (including the modified example) can be formed of an analog circuit or a digital circuit, as described in the first embodiment.

  Further, the sound reproduction system 1 may be realized by creating a computer program corresponding to the configuration of the digital circuit described above and causing the microprocessor (MPU) or digital signal processor (DSP) to execute the computer program.

  Alternatively, an APF (adaptive phase filter) may be used as the phase adjuster 2 to exhibit a substantially constant phase characteristic in the frequency band PBW described above.

  Next, a more specific embodiment will be described with reference to FIG. FIGS. 4A, 4B, and 4C are block diagrams showing the configuration of the sound reproduction system of the present embodiment, and the same or corresponding parts as those in FIG. 2A are denoted by the same reference numerals. 4D, 4E, and 4F are explanatory diagrams for explaining the function.

  The sound reproduction system 1 of the present embodiment shown in FIG. 4A includes a phase adjuster 2 having two phase shift circuits 2L and 2R, subtractors 3L and 3R, bandpass filters 4L and 4R, and an amplifier 6L. 6R, and as shown in FIG. 1B, multi-channel surround reproduction is performed by driving the speakers FL, FR, RL, RR provided in the passenger compartment of the automobile.

  Here, as shown in FIG. 4B, the phase shift circuit 2L includes a high-pass filter HPFL1, a low-pass filter LPFL2, and a high-pass filter HPFL1, which receive a 2-channel stereo audio signal (left-channel audio signal) Lin. An adder AL for adding (synthesizing) the output and the output of the low-pass filter LPFL2 is formed.

  Furthermore, as shown in the frequency-to-phase characteristic of FIG. 4D, the high-pass filter HPFL1 has a phase at a low frequency of approximately 0 and a phase φL1 at a high frequency range of approximately π with a cutoff frequency of 500 Hz as a boundary. The low-pass filter LPFL2 is set to / 2 (advanced phase), and the phase at the low frequency is almost 0 and the phase φL2 at the higher frequency range is approximately −π / 2 (late phase) with the cutoff frequency of 500 Hz as a boundary. Is set to

  As shown in FIG. 4C, the phase shift circuit 2R includes a high-pass filter HPFR1 and a low-pass filter LPFR2 for inputting a 2-channel stereo audio signal (right-channel audio signal) Rin, an output of the high-pass filter HPFR1, and a low-pass filter. An adder AR for adding (synthesizing) the output of the filter LPFR2 is formed.

  Further, as shown in the frequency-to-phase characteristic of FIG. 4E, the high-pass filter HPFR1 has a phase at a low frequency of approximately 0 and a phase φR1 at a high frequency range of approximately π with a cutoff frequency of 200 Hz as a boundary. The low-pass filter LPFR2 is set to / 2 (advanced phase), and the phase at the low frequency is almost 0 and the phase φR2 at the higher frequency range is approximately −π / 2 (late phase) with the cutoff frequency 200 Hz as a boundary. Is set to

  Furthermore, the gains in the passbands of the high pass filters HPFL1, HPFR1 and the low pass filters LPFL2, LPFR2 are substantially equal.

  Then, the phase shift circuit 2L shifts the left channel audio signal Lin in the above-described phases φL1 and φL2, and supplies the phase shifted signal as the left channel audio signal L to the front speaker FL. Further, the phase shift circuit 2R shifts the right channel audio signal Rin in the above-mentioned phases φR1 and φR2, and supplies the phase shifted signal to the front speaker FR as the right channel audio signal R.

  Here, the phase difference φLR between the audio signal L phase-shifted by the phases φL1 and φL2 and the audio signal R phase-shifted by the phases φR1 and φR2 in the frequency range from 200 Hz to 500 Hz is shown in FIG. As shown, the phase difference is approximately π (180 °), and the phase difference outside the frequency range from 200 Hz to 500 Hz is approximately zero. That is, the phase difference in the frequency range from 200 Hz to 500 Hz is π represented by the difference between the phases φR1 and φR2 (φR1−φR2).

  From this, the phase shift circuits 2L and 2R can relatively shift the phase between both the audio signals Lin and Rin within a frequency range of 200 Hz to 500 Hz by approximately π (180 °), and the phase adjustment thereof. The audio signals L and R subjected to are supplied to the front speakers FL and FR.

  The amplifier 6L is a variable gain amplifier for adjusting the amplitude of the right channel audio signal Rin, and the amplifier 6R is a variable gain amplifier for adjusting the amplitude of the left channel audio signal Lin.

  Then, the subtractor 3L generates a difference signal (Lin−αRin) between the audio signal Lin and the audio signal (αRin) amplified by the gain α of the amplifier 6L by the subtraction process, and the subtractor 3R performs the audio by the subtraction process. A difference signal (Rin−βLin) between the signal Rin and the audio signal (βLin) amplified by the gain β of the amplifier 6R is generated.

  The band pass filter 4L has a pass bandwidth BW of 200 Hz to 500 Hz, and supplies a signal that passes through the pass bandwidth BW of the difference signal (Lin−αRin) to the rear speaker RL as a surround sound signal SL.

  Similarly, the band pass filter 4R has a pass bandwidth BW of 200 Hz to 500 Hz, and supplies a signal passing through the pass bandwidth BW of the difference signal (Rin−βLin) to the rear speaker RR as a surround sound signal SR.

  According to the sound reproduction system 1 of the present embodiment having such a configuration, the phase shift circuits 2L and 2R relatively shift the phase by π between the audio signals Lin and Rin in the frequency band from 200 Hz to 500 Hz. The phase-shifted signals are supplied to the front speakers FL and FR as a left channel audio signal L and a right channel audio signal R, respectively, and sounded. For this reason, both reproduced sounds emitted from the front speakers FL and FR can be made substantially in phase with each other to reach the listener's left and right ears, and the listener can feel a sense of discomfort.

  Further, since the surround signals SL and SR supplied from the bandpass filters 4L and 4R to the rear speakers RL and RR are generated from the difference signals (Lin−αRin) and (Rin−βLin), their phases are π (180). °) will shift. For this reason, both reproduced sounds emitted from the rear speakers RL and RR based on the surround signals SL and SR reach the left and right ears of the listener in substantially positive phase with each other. For this reason, it is possible to reduce a sense of discomfort for the listener.

  As described above, the phase shift circuits 2L and 2R are formed of the high-pass filters HPFL1 and HPFR2 and the low-pass filters LPFL1 and LPFR2. However, as described in the first embodiment, each has predetermined phase characteristics. A phase shift circuit having a filter bank structure that exhibits a substantially constant phase characteristic in the frequency band from 200 Hz to 500 Hz by appropriately combining a band pass filter, a high pass filter, and a low pass filter that are connected in parallel or in series. You may make it form.

  Further, the phase shift circuits 2L and 2R in FIG. 4A are configured by an APF (adaptive phase filter), and relative to each other with respect to the audio signals Lin and Rin in the frequency band from 200 Hz to 500 Hz described above. The phase-shifted signal may be supplied to the front speakers FL and FR as the left channel audio signal L and the right channel audio signal R.

  In addition, as shown in FIG. 2, the audio signals L and R and the surround audio signals SL and SR are added to the front speakers FL and FR, respectively, and the surround audio signals SL and SR are supplied to the rear speakers RL. , RR may be configured to be supplied.

  Similarly to the case shown in FIG. 3, the audio signals L and R and the surround audio signals SL and SR are added to the front speakers FL and FR, respectively, and the audio signals L and R and the surround audio signal are supplied. The configuration may be such that SL and SR are added and supplied to the rear speakers RL and RR.

FIG. 1A is a block diagram showing a configuration of a conventional sound reproduction system, and FIG. 1B is an explanatory diagram for explaining positions of speakers provided in a vehicle interior. FIG. 2A is a block diagram illustrating the configuration of the sound reproduction system according to the first embodiment, and FIG. 2B is a block diagram illustrating the configuration of the sound reproduction system according to the second embodiment. It is a block diagram showing the structure of the modification of the sound reproduction system shown in FIG.2 (b). 4A, 4B, and 4C are block diagrams showing the configuration of the sound reproduction system of the first embodiment, and FIGS. 4D, 4E, and 4F are shown in FIGS. 4B and 4C. It is explanatory drawing for demonstrating the frequency versus phase characteristic and function of a high-pass filter and a low-pass filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sound reproduction system 2 ... Phase adjuster 4L, 4R ... Band pass filter FL, FR ... Front speaker RL, RR ... Rear speaker

Claims (5)

Artificially generating the surround signal from the audio signal and the right channel audio signal of the left channel of a stereo scheme, provided to the offset position of each of the left and right front speakers and the listener provided offset position of the left and right of the listener more each rear speakers were, a sound reproduction system to perform a multi-channel surround reproduction,
The reproduction sound emitted from each front speaker reaches the left and right ears of the listener in the frequency range when the binaural correlation function of the reproduction sound emitted from each front speaker is negative. Phase adjusting means for relatively phase-shifting the audio signal of the left channel and the audio signal of the right channel at a phase corresponding to the time difference required, and supplying the phase to the front speakers;
A first surround signal is generated by subtracting the right channel audio signal from the left channel audio signal, and a second surround signal is generated by subtracting the left channel audio signal from the right channel audio signal. Surround signal generating means;
And extracting a signal component of the frequency range from the first surround signal and the second surround signal, and supplies the signal component extracted from the first surround signal to the left rear speaker, extracted from the second surround signal Filter means for supplying the processed signal component to the right rear speaker ;
A sound reproduction system comprising: An adder that synthesizes the signal component extracted by the filter and the signal phase-shifted by the phase adjuster and supplies the synthesized signal to each front speaker;
The sound reproduction system according to claim 1. An adder that synthesizes the signal component extracted by the filter and the signal phase-shifted by the phase adjuster and supplies the synthesized signal to each rear speaker;
The sound reproduction system according to claim 1. The frequency range is 200 Hz to 500 Hz, and the phase is π.
The sound reproduction system according to claim 1 or 2, characterized by the above-mentioned. Artificially generating the surround signal from the audio signal and the right channel audio signal of the left channel of a stereo scheme, provided to the offset position of each of the left and right front speakers and the listener provided offset position of the left and right of the listener more each rear speakers were, a sound reproducing method for causing the multi-channel surround reproduction,
The reproduction sound emitted from each front speaker reaches the left and right ears of the listener in the frequency range when the binaural correlation function of the reproduction sound emitted from each front speaker is negative. A phase adjustment step in which the left channel audio signal and the right channel audio signal are relatively phase-shifted in a phase corresponding to the time difference required and supplied to the front speakers;
A first surround signal is generated by subtracting the right channel audio signal from the left channel audio signal, and a second surround signal is generated by subtracting the left channel audio signal from the right channel audio signal. Surround signal generation process,
And extracting a signal component of the frequency range from the first surround signal and the second surround signal, and supplies the signal component extracted from the first surround signal to the left rear speaker, extracted from the second surround signal A filter process for supplying the processed signal component to the right rear speaker ;
A sound reproduction method comprising:

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