JP5055967B2 - Audio playback device - Google Patents

Description

  The present invention relates to an audio playback device.

  As multi-channel stereo or surround stereo, for example, there is so-called 5.1-channel stereo. In this 5.1 channel stereo playback device, for example, as shown in FIG. 14, speakers SPLF, SPRF, SPCF are arranged around the listener LSNR, that is, on the left front, right front, and center front, respectively, and left rear (or Speakers SPLB and SPRB are arranged on the left side and the right rear side (or right side), respectively, and in FIG. 14, a subwoofer SPSW is arranged behind the listener LSNR.

  14, 5.1 channel digital audio data encoded by a predetermined method is output from the DVD player 1, and this digital audio data is supplied to the decoder circuit 2 and decoded. Thus, from the decoder circuit 2, the channel audio signals SLF, SRF, SCF, SLB corresponding to the left front, right front, center front, left rear (or left side), right rear (or right side) of the listener LSNR, SRB is extracted, and a low frequency component SSW that does not give a sense of direction, for example, a low frequency component SSW of 150 Hz or less is extracted.

  These signals SLF to SRB and SSW are supplied to the speakers SPLF to SPRB and SPSW through the power amplifiers 4LF to 4RB and 4SW, respectively. Therefore, according to this playback apparatus, the listener LSNR can listen to 5.1 channel surround stereo.

For example, there are the following prior art documents.
JP 2001-352599 A

  However, in the above-described reproducing apparatus, the subwoofer SPSW is in charge of reproducing the low-frequency component SSW of all channels. For this reason, in order to obtain a larger bass feeling, a considerably large signal (power) must be supplied to the subwoofer SPSW, and the subwoofer SPSW may be damaged due to excessive input.

  Further, if it can withstand a larger input, the subwoofer SPSW becomes larger and the power amplifier 4SW also needs to have a larger output, resulting in a larger device.

  The present invention is intended to solve such problems.

In order to solve such a problem, in the present invention, multi-channel audio reproduction is performed by supplying audio signals of channels corresponding to the positions of the speakers to a plurality of channels of speakers arranged around the listener. For a stereo audio playback device, when f0 is the resonance frequency of the speaker and f1 is the upper limit of the frequency that does not cause a sense of incongruity in the resulting multiplied wave component when the fundamental wave component of a signal is multiplied , A harmonic generation circuit for generating a harmonic component having a double frequency by multiplying a low frequency component of the low frequency component for subwoofer included in the band f0 / 2 to f1 / 2, Each audio signal is supplied, and the audio signal of each channel is converted to the harmonic signal generated by the harmonic generation circuit. A plurality of adder circuits that add and output at a predetermined ratio so as to be distributed to each other, a plurality of amplifiers that supply each output of each adder circuit to the speaker of each channel, and the level of the audio signal of each channel are detected Then, a plurality of level detection circuits for outputting a level detection signal indicating the detected level, and a harmonic overtone component generated by the harmonic overtone generation circuit are supplied, and harmonics are generated based on the level detection signals output from the level detection circuits. A plurality of level control circuits that control component levels and output to each adder circuit, and level detection signals are supplied from each level detection circuit, and the ratio of the level detection signals to the sum of the level detection signals for each channel determine the provided and a determination control circuit for outputting a determination signal indicating the determination result to the level control circuit, respectively Unishi by the level control circuit, based on a discrimination signal of each channel supplied from the discrimination control circuit, the harmonic signal generated by the harmonic generator to distribute by weighting the respective channels, the level of the harmonic components Is controlled and output to each adder circuit .

According to the present invention, a multi-channel stereo audio reproduction device is configured to perform audio reproduction by supplying audio signals of channels corresponding to the positions of the speakers to a plurality of channels of speakers arranged around the listener. On the other hand, when f0 is the resonance frequency of the speaker and f1 is multiplied by the fundamental wave component of a signal, the resulting multiplied wave component is the upper limit of the frequency that does not cause a sense of discomfort in the subwoofer. A harmonic generation circuit for generating a harmonic component of a double frequency by multiplying a low frequency component in which the frequency of the low frequency component is included in the band f0 / 2 to f1 / 2, and an audio signal for each channel are supplied. A predetermined ratio so that the harmonic signal generated by the harmonic generation circuit is distributed to each channel. In addition, a plurality of adder circuits that add and output in each step, a plurality of amplifiers that supply each output of each adder circuit to the speaker of each channel, and a level of the audio signal of each channel are detected, and the detected level is determined. A plurality of level detection circuits that output level detection signals to be shown and a harmonic component generated by the harmonic generation circuit are respectively supplied, and the level of the harmonic component is controlled based on the level detection signal output from each level detection circuit. A plurality of level control circuits output to the adder circuit and level detection signals are supplied from the level detection circuits, respectively, and the ratio of the level detection signal to the sum of the level detection signals is determined for each channel, and the determination result acceptable to provide a discrimination control circuit which outputs to each level control circuit determination signal indicating each respective level control circuit Further, based on the discrimination signal for each channel supplied from the discrimination control circuit, each adder circuit controls the level of the harmonic component so that the harmonic signal generated by the harmonic generation circuit is weighted and distributed to each channel. Even if a subwoofer is placed around the listener, even if the subwoofer and its drive power amplifier are small, or even if no subwoofer is placed around the listener, A rich bass sound can be obtained through the speaker of each channel, and the level of the harmonic component distributed to each channel is changed according to the level of the audio signal of that channel, and the burden on the speaker and power amplifier Can be dispersed and lightened .

[1] Overtone component As is well known, the sound of a musical instrument is composed of a fundamental tone and its overtone, and the proportion of them determines the timbre. It has been demonstrated psycho-acoustically that human perception is perceived as if the fundamental tone is being output if the harmonic is output even if the fundamental tone is not output.

  The present invention pays attention to such points. By forming the harmonic component from the low frequency component SSW (or a part thereof) and distributing the harmonic component to each channel, a greater sense of bass can be obtained. At the same time, the burden on the subwoofer SPSW and the power amplifier 4SW is reduced.

[2] First Example FIG. 1 shows an example in which the present invention is applied to a 5.1 channel stereo reproducing apparatus. That is, 5.1 channel digital audio data encoded by a predetermined method is output from a signal source, for example, a DVD player 1, and this digital audio data is supplied to the decoder circuit 2 and decoded. Thus, from the decoder circuit 2, the audio signals SLF, SRF, SCF, and SLB of each channel corresponding to the left front, right front, center front, left rear (or left side), and right rear (or right side) of the listener LSNR. , SRB is extracted, and a low frequency component SSW that does not give a sense of direction, for example, a low frequency component SSW of 150 Hz or less is extracted.

  In this case, the audio signals SLF to SRB of the respective channels can be considered as signals obtained by removing or attenuating the low-frequency component SSW by supplying the original audio signal to the high-pass filter, and the low-frequency component SSW is the original audio signal. It can be considered as a signal component extracted by supplying a signal to a low-pass filter.

  The signals SLF to SRB are supplied to the speakers SPLF to SPRB through the addition circuits 3LF to 3RB and further through the power amplifiers 4LF to 4RB. Further, the low frequency component SSW is supplied to the speaker SPSW through the power amplifier 4SW. In this case, as described with reference to FIG. 14, for example, the speakers SPLF to SPRB are arranged around the listener, for example, left front, right front, center front, left rear (or left side), right rear (or right side). In addition, the speaker SPSW is disposed at an arbitrary place, for example, at the rear.

  Further, the low frequency component SSW extracted from the decoder circuit 2 is supplied to the overtone forming circuit 5. An example of the harmonic generation circuit 5 will be described later. As shown in FIGS. 2A and 2B, the low-frequency component having a frequency band of f0 / 2 to f1 / 2 is included in the low-frequency component SSW supplied thereto. SBS is doubled to twice the frequency f0 to f1 to generate a harmonic component SHT.

here,
f0: Resonant frequency of the speakers SPLF to SPRB. For example, f0 = 100Hz
f1: An upper limit value of the frequency (frequency of the signal of the multiplication result) that does not cause a sense of incongruity in the auditory sensation of the resultant multiplied wave component when the fundamental wave component of a certain signal is multiplied. Generally about 200Hz.
It is.

  In general, when an audio signal having a resonance frequency f0 or less is supplied to a speaker, the output sound pressure of the fundamental wave component decreases and the distortion component (harmonic component) increases rapidly as the frequency decreases. Tend. Therefore, an audio device using a speaker having a small diameter cannot sufficiently reproduce a bass sound having a resonance frequency f0 or less of the speaker.

  Then, the harmonic component SHT is supplied to the adder circuits 3LF to 3RB, added to the audio signals SLF to SRB at a predetermined rate, and distributed to each channel.

  According to such a configuration, the speakers SPLF to SPRB output sound based on the audio signals SLF to SRB, and the speaker SPSW outputs low sound based on the low frequency component SSW. Will be able to.

  In this case, since the harmonic components SHT are added to the audio signals SLF to SRB supplied to the speakers SPLF to SPRB through the adding circuits 3LF to 3RB, the harmonics based on the harmonic components SHT are output from the speakers SPLF to SPRB. Will also be output. Since the overtone component SHT output as this overtone has the low-frequency component SBS as the fundamental wave component, the low-frequency component SBS is perceived by the overtone, and therefore a low-frequency sound can be obtained.

  As a result, the low-frequency component SSW input to the subwoofer SPSW can be reduced, so that the subwoofer SPSW can be prevented from being damaged due to excessive input. Further, since the subwoofer SPSW does not need to withstand a large input, it is not necessary to increase the size and the power amplifier 4SW does not need to have a large output.

  At this time, the harmonic signals SHT are added to the audio signals SLF to SRB supplied to the speakers SPLF to SPRB, but the harmonic components SHT are distributed to the audio signals SLF to SRB of five channels. Therefore, each signal level (power) is small, and therefore it is hardly a burden for the speakers SPLF to SPRB and the power amplifiers 4LF to 4RB.

  Thus, according to this playback device, the harmonic component SHT of the low-frequency component SBS is distributed to each channel of the surround stereo to output harmonics, so that a greater bass feeling can be obtained, and the subwoofer SPSW and power The burden on the amplifier 4SW can be reduced. Further, since the low-frequency component SSW is also output as sound by the subwoofer SPSW, a richer bass feeling can be obtained.

[3] Second Example FIG. 3 shows another example in which the present invention is applied to a 5.1 channel stereo reproducing apparatus. That is, in this example as well, the signal lines from the decoder circuit 2 to the speakers SPLF to SPRB are configured in the same manner as that in FIG. 1, but the power amplifier 4SW and the subwoofer SPSW in FIG. 1 are omitted.

  Therefore, in this case, although it is not possible to obtain a low tone from the subwoofer SPSW, as described in [2], the harmonic component SHT of the low frequency component SHT is supplied to the speakers SPLF to SPRB and output as a harmonic. Therefore, a low-pitched feeling can be obtained. Since the power amplifier 4SW and the subwoofer SPSW are omitted, the cost can be reduced and the system can be simplified.

[4] Third Example FIG. 4 shows a case where the present invention is applied to a 5.1 channel stereo reproducing apparatus and the distribution amount of the harmonic component SHT is changed in accordance with the signal level of each channel.

  That is, also in this example, the signal lines from the decoder circuit 2 to the speakers SPLF to SPRB and SPSW are configured in the same manner as that in FIG. 1, but the harmonic component SHT output from the harmonic generation circuit 5 is the level control circuit. The signals are supplied to the adder circuits 3LF to 3RB through 6LF to 6RB, respectively. The audio signals SLF to SRB output from the decoder circuit 2 are supplied to the level detection circuits 7LF to 7RB to detect the levels of the audio signals SLF to SRB, respectively, and the detection signals are sent to the level control circuits 6LF to 6RB. It is supplied as the control signal.

  In this case, the level detection in the level detection circuits 7LF to 7RB can be an absolute value of the signal level or its envelope. For example, when the detection circuit 7LF detects that the level of the audio signal SLF is high, the audio signal is reversed so that the level of the overtone component SHT supplied from the level control circuit 6LF to the addition circuit 3LF becomes small. When the detection circuit 7LF detects that the SLF level is low, the level control circuit 6LF is controlled so that the level of the harmonic overtone component SHT supplied from the level control circuit 6LF to the addition circuit 3LF is increased.

  That is, the level control circuit 6LF is controlled in such a direction that the output level of the adder circuit 3LF becomes constant. Similarly, the other level control circuits 6RF to 6RB are controlled so that the output levels of the addition circuits 3RF to 3RB become constant.

  Therefore, also in this reproducing apparatus, a low tone can be obtained by the harmonics output from the speakers SPLF to SPRB, and at this time, the level of the harmonic component SHT distributed to each channel is the original audio in the channel. Since it changes corresponding to the signals SLF to SRB, the burden on the speakers SPLF to SPRB and the power amplifiers 4LF to 4RB is dispersed and lightened.

[5] Fourth Example FIG. 5 shows a case where the harmonic component SHT is distributed to each channel, and the distribution of the harmonic component SHT is weighted according to the signal level of each channel.

That is, also in this example, the signal lines from the decoder circuit 2 to the speakers SPLF to SPRB and SPSW are configured in the same manner as that of FIG. 4, and the harmonic component SHT output from the harmonic generation circuit 5 is a level control circuit. The signals are supplied to the adder circuits 3LF to 3RB through 6LF to 6RB, respectively. The audio signals SLF to SRB output from the decoder circuit 2 are supplied to the level detection circuits 7LF to 7RB, the levels of the audio signals SLF to SRB are detected, and the detection signals are supplied to the discrimination control circuit 8. .

The discrimination control circuit 8 corresponds to the ratio of the audio signals SLF to SRB in each channel with respect to the sum of the audio signals SLF to SRB output from the decoder circuit 2, and the magnitude of the harmonic component SHT distributed to each channel. Is to control. For this reason, the ratio of the detection outputs to the sum of the detection outputs of the detection circuits 7LF to 7RF is determined for each channel, and a signal of the determination result is supplied to the level control circuits 6LF to 6RB as the control signal.

  For example, when the level of the audio signal SLF relative to the sum of the audio signals SLF to SRB is large, the audio signals SLF to SRB are conversely set so that the level of the harmonic component SHT supplied from the level control circuit 6LF to the adding circuit 3LF is small. When the level of the audio signal SLF with respect to the sum total is small, the level control circuit 6LF is controlled so that the level of the overtone component SHT supplied from the level control circuit 6LF to the addition circuit 3LF becomes large. The other level control circuits 6RF to 6RB are similarly controlled.

  Further, the overtone component SHT output from the overtone generation circuit 5 is supplied to the detection circuit 9 to detect the level thereof, and the detection output is supplied to the discrimination control circuit 8, and the control signal SCTL that can be changed by a listener, for example. Is supplied to the discrimination control circuit 8, and the total amount of the overtone components SHT supplied to the adder circuits 6LF to 6RB is set to an appropriate value in advance.

  Therefore, also in this reproducing apparatus, a low tone can be obtained by the harmonics output from the speakers SPLF to SPRB, and at this time, the level of the harmonic component SHT distributed to each channel is the original audio in the channel. Since it changes corresponding to the signals SLF to SRB, the burden on the speakers SPLF to SPRB and the power amplifiers 4LF to 4RB is dispersed and lightened.

[6] Example of Weighting Method for Distributing Overtone Component SHT FIGS. 6 and 7 are examples of flowcharts specifically showing the processing contents of the discrimination control circuit 8 of FIG. In this case, the discrimination control circuit 8 is constituted by a microcomputer, and the routine 100 in the flowcharts shown in FIGS. 6 and 7 is executed by the microcomputer for each sample of the signals SLF to SRB, for example.

In the following description, each of the audio signals SLF to SRB is a digital signal, and has a maximum value of 1.0 (0 dB) when full bit. Also,
ALF to ARB: Levels of signals SLF to SRB AHT: Level of harmonic component SHT detected by detection circuit 9 GLF to GRB: Gain of level control circuits 6LF to 6RB GTTL: Target gain of harmonic component SHT
The gain is necessary to obtain the total amount of harmonic components SHT set in advance.

The processing of the microcomputer constituting the discrimination control circuit 8 starts from step 101 of the routine 100. Next, in step 102, the signal levels ALF to ARB are
All levels ALF to ARB ≤ level (1.0-GTTL / 5 x AHT) (1)
It is determined whether or not.

If (1) holds, the process proceeds from step 102 to step 111, where the distribution of the harmonic component SHT is set to the “equal distribution mode”. That is, the gains GLF to GRB of the level control circuits 6LF to 6RB are
GLF = GRF = GCF = GLB = GRB = GTTL / 5
After that, the process proceeds to step 112 and the routine 100 is terminated.

  Therefore, when (1) is satisfied, that is, when all the levels of the audio signals SLF to SRB are smaller than the specified value, the overtone component SHT is evenly distributed to all the audio signals SLF to SRB.

  On the other hand, if (1) is not satisfied in step 102, that is, if at least one level of the signals SLF to SRB is greater than the right side of (1), the process proceeds from step 102 to step 121. In step 121 and subsequent steps, the distribution of the overtone component SHT is set to the “small level channel priority distribution mode”.

That is, first, in step 121, the signals SLF to SRB output from the decoder circuit 2 are rearranged with the signals S1, S2, S3, S4, and S5 in ascending order of the levels ALF to ARB. For example, if the level of the signal SRB is minimum, S1 = SRB. In the following,
A1 to A5: Levels of signals S1 to S5. A1 ≦ A2 ≦ A3 ≦ A4 ≦ A5
61 to 65: level control circuit to which signals S1 to S5 are supplied
This is one of the level control circuits 6LF to 6RB. G1 to G5: The gain of the level control circuits 61 to 65.

Next, at step 122,
(1.0−A1) / AHT ≧ GTTL (2)
Whether or not is satisfied is determined. That is, the gain (the gain G1 of the level control circuit 61) for making the level A1 of the signal S1 having the minimum level full bit is calculated by the left side of (2) (1.0-A1) / AHT, and this calculated value is It is determined whether or not the total gain is equal to or greater than GTTL.

If the calculated value is equal to or greater than the total gain GTTL, that is, if (2) is satisfied, the process proceeds from step 122 to step 123, where the gain G1 of the level control circuit 61 is obtained. But,
G1 = GTTL
And the gains G2 to G5 of the level control circuits 62 to 65 are
G2 = G3 = G4 = G5 = 0
After that, the routine 100 is ended by step 124.

  Accordingly, when (2) is established, the harmonic component SHT is output from the level control circuit 61 only after being multiplied by the value GTTL and added to the audio signal of the corresponding channel.

If (2) is not satisfied in step 122, the signal S2 having the second lowest level is processed in the same manner. That is, the microcomputer processing in the discrimination control circuit 8 proceeds from step 122 to step 131, where the gain G1 of the level control circuit 61 is
G1 = (1.0-A1) / AHT
Set to

Then, in step 132,
G1 + (1.0-A2) / AHT ≧ GTTL (3)
Whether or not is satisfied is determined. If (3) holds, the process proceeds from step 132 to step 133, where the gains G2 to G5 of the level control circuits 62 to 65 are
G2 = GTTL-G1
G3 = G4 = G5 = 0
After that, the routine 100 is ended by step 124.

  Therefore, when (3) is established, the harmonic component SHT is output only from the level control circuits 61 and 62, added to the audio signal of the corresponding channel, and since A1 <A2, the harmonic component SHT. Will be distributed more to channels with lower audio signal levels.

Furthermore, if (3) is not satisfied in step 132, the process proceeds from step 132 to step 141, where the gain G2 of the level control circuit 62 is
G2 = (1.0-A2) / AHT
Set to

Then, in step 142,
G1 + G2 + (1.0-A3) / AHT ≧ GTTL (4)
Whether or not is satisfied is determined. If (4) is established, the process proceeds from step 142 to step 143. In this step 143, the gains G3 to G5 of the level control circuits 63 to 65 are
G3 = GTTL-G1-G2
G4 = G5 = 0
After that, the routine 100 is ended by step 124.

  Therefore, when (4) is established, the harmonic component SHT is output from the level control circuits 61 to 63, added to the audio signal of the corresponding channel, and since A1 <A2 <A3, the harmonic component More SHT will be distributed to channels with lower audio signal levels.

Similarly, if (4) is not satisfied in step 142, the process proceeds from step 142 to step 151, where the gain G3 of the level control circuit 63 is
G3 = (1.0-A3) / AHT
Set to

Then, in step 152,
G1 + G2 + G3 + (1.0-A4) / AHT ≧ GTTL (5)
Whether or not is satisfied is determined. If (5) holds, the process proceeds from step 152 to step 153, where the gains G4 and G5 of the level control circuits 64 and 65 are
G4 = GTTL-G1-G2-G3
G5 = 0
After that, the routine 100 is ended by step 124.

  Therefore, when (5) is established, the harmonic component SHT is output from the level control circuits 61 to 64 and distributed to the corresponding channels, and since A1 <A2 <A3 <A4, the harmonic component SHT. Will be distributed more to channels with lower audio signal levels.

If (5) is not satisfied in step 152, the process proceeds from step 152 to step 161. In step 161, the gain G4 of the level control circuit 64 is
G4 = (1.0-A4) / AHT
Set to

Then, in step 162,
G1 + G2 + G3 + G4 + (1.0-A5) / AHT ≧ GTTL (6)
Whether or not is satisfied is determined. If (6) is established, the process proceeds from step 162 to step 163. In this step 163, the gain G5 of the level control circuit 65 is
G5 = GTTL-G1-G2-G3-G4
After that, the routine 100 is ended by step 124.

Further, if (6) is not satisfied in step 162, the process proceeds from step 162 to step 164, in which the gain G5 of the level control circuit 65 is
G5 = (1.0-A5) / AHT
After that, the routine 100 is ended by step 124.

  Thus, according to the routine 100, when the overtone component SHT is distributed to each channel of the audio signals SLF to SRB, the overtone component SHT is preferentially distributed to the channels having a low audio signal level among the channels. Therefore, when the harmonic component SHT is distributed to each channel, more harmonic components SHT can be distributed to each channel without overflowing.

[7] First Example of Harmonic Generation Circuit FIG. 8 shows an example of the harmonic generation circuit 5. That is, the low frequency component SSW extracted from the decoder circuit 2 is supplied to the bandpass filter 52 through the input terminal 51. For example, as shown in FIGS. 9A and 9B, among the low frequency components SSW supplied thereto, A low-frequency component S52 (= SBS) having a frequency band of f0 / 2 to f1 / 2 is taken out, and this low-frequency component S52 is supplied to the multiplication circuit 53, and as shown in FIG. The signal component S53 is extracted to the output terminal 54 as a harmonic component SHT.

  In this case, the multiplication circuit 53 can be configured as shown in FIG. 10, for example. That is, in FIG. 10, reference numeral 53M denotes a memory circuit that is configured by, for example, a ring buffer and has a substantially sufficient address (capacity). Further, the low frequency component S52 is digital data, but when D / A (Digital to Analog) conversion is performed, for example, a waveform as shown in FIG. 11A is assumed.

  Furthermore, a time point at which the polarity of the low frequency component S52 is reversed from negative to positive is defined as a time point tx. Further, a period from a certain time point tx to the next time point tx, that is, one cycle period of the low frequency component S52 is defined as a period Tx.

  In FIG. 10, the low frequency component S52 is supplied to the memory circuit 53M through the input terminal 53A. As shown in FIG. 11A, the low frequency component S52 is sequentially written to each address of the memory circuit 53M for each sample. It will be.

  Simultaneously with this writing, the low frequency component S52 written in the memory circuit 53 in the previous period Tx is read from the memory circuit 53M. In FIG. 11, for the sake of simplicity, for one cycle of the low frequency component S52, it is assumed that the one cycle period Tx in which the writing is performed and the one cycle period Tx in which the reading is performed are the same.

  Reading from the memory circuit 53M is performed by thinning out at a rate of one address per two addresses at the same clock frequency as that at the time of writing. Further, the reading is repeated twice in the period Tx. Accordingly, as shown in FIG. 11B, the read signal becomes a signal S53 having a frequency twice that of the original low-frequency component S52 (= SBS), and can be extracted as a harmonic component SHT.

[8] Second Example of Overtone Generation Circuit FIG. 12 shows another example of the overtone generation circuit 5. That is, in this example, as in the case of [7], the band pass filter 52 and the multiplier circuit 53 form a double harmonic component S53 (FIG. 9B), and this double harmonic component S53 is supplied to the adder circuit 55. Supplied.

  Further, the low-frequency component SSW supplied to the input terminal 51 is also supplied to the band-pass filter 56, and as shown in FIG. 9C, a low-frequency component S56 having a frequency band of f0 / 4 to f1 / 4 is extracted. This low-frequency component S56 is supplied to the multiplication circuit 57 to be a harmonic component S57 having a quadruple frequency f0 to f1 as shown in FIG. 9D, and this harmonic component S57 is supplied to the addition circuit 55.

  Therefore, the addition circuit 55 outputs an addition signal of the double harmonic component S53 (FIG. 9B) and the quadruple harmonic component S57 (FIG. 9D), and this addition output is output to the output terminal 54 as the harmonic component SHT. It is taken out.

  In this case, for example, as shown in FIG. 13A (the symbol FSP indicates the frequency characteristics of the speakers SPLF to SPRB), if the frequency of the low frequency component S52 (S56) is 35 Hz, the low frequency component S52 is doubled. Even if the overtone component S53 (shown by a broken line) is formed, its frequency is 70 Hz and cannot be sufficiently reproduced by the speakers SPLF to SPRB.

  However, in the overtone generation circuit 5 of FIG. 12, if the frequency of the low-frequency component S56 (S52) is 35 Hz, the low-frequency component S56 is supplied to the multiplication circuit 57 through the band-pass filter 56, and the quadruple frequency 140 Hz. Harmonic component S57 (shown by a solid line) is formed, and this harmonic component S57 is supplied to the adding circuit 55. Therefore, even if the frequency of the low-frequency component S52 (S56) is 35 Hz, a low-frequency sensation corresponding to the low-frequency component S52 can be obtained by the harmonic component S57 having a frequency four times that frequency.

  For example, as shown in FIG. 13B, if the frequency of the low frequency component S56 (S52) is 60 Hz, when the harmonic component S57 (shown by a broken line) having a frequency four times that of the low frequency component S56 is formed, the frequency is Since it is 240 Hz and exceeds the upper limit frequency f1 (≈200 Hz) for adding overtones, if this overtone component S57 is supplied to the speakers SPLF to SPRB, an uncomfortable sound is output.

  However, in the overtone generation circuit 5 of FIG. 12, if the frequency of the low-frequency component S56 is 60 Hz, this low-frequency component S56, that is, the low-frequency component S52 is supplied to the frequency multiplier 53 through the band-pass filter 52. A harmonic component S53 having a double frequency of 120 Hz (shown by a solid line) is provided, and this harmonic component S53 is supplied to the adding circuit 55. Therefore, even if the frequency of the low-frequency component S56 (S52) is 60 Hz, a low-frequency sensation corresponding to the low-frequency component S56 can be obtained by the harmonic component S53 having twice the frequency.

[9] Summary According to the above-described playback device, the harmonic component SHT of the low-frequency component SBS is distributed to each channel, and the harmonics are output from the speakers SPLF to SPRB, so the subwoofer SPSW and its drive Even if the power amplifier 4SW is small, it is possible to obtain a low-pitched sound equivalent to that of a large one.

  In addition, since the harmonic component SHT is distributed to each channel, the burden on the power amplifier or speaker of a specific channel does not increase.

[10] Others In the above description, the frequency f0 is the resonance frequency of the speaker 5. However, in an actual product, it can be set to another frequency corresponding to the frequency at which a low-frequency sound is desired. Also in the reproducing apparatus of FIG. 4 or FIG. 5, the subwoofer SPSW and its power amplifier 4SW can be omitted as in the reproducing apparatus of FIG.

  Furthermore, in the above description, the present invention is applied to a 5.1 channel stereo playback device, but the present invention can also be applied to multichannel stereo such as 2.1 channel stereo and 4.1 channel stereo.

  In the above description, the harmonic component is preferentially distributed to the channel with a low level of the original audio signal, but conversely, it can be preferentially distributed from the channel with a high level. Furthermore, when the harmonic component is distributed, it can be distributed preferentially from a specific channel, for example, the front channel. That is, it is possible to weight the distribution of harmonic components. Further, the routine 100 can be executed in units of one cycle period Tx.

It is a systematic diagram showing one embodiment of the present invention. It is a frequency characteristic figure for demonstrating the apparatus of FIG. It is a systematic diagram which shows the other form of this invention. It is a systematic diagram which shows the other form of this invention. It is a systematic diagram which shows the other form of this invention. It is a flowchart which shows a part of one form of the routine which controls operation | movement of the apparatus of FIG. 7 is a flowchart showing a continuation of the routine of FIG. It is a systematic diagram which shows one form of a part of apparatus of this invention. It is a frequency characteristic figure for demonstrating the apparatus of FIG. It is a systematic diagram which shows one form of a part of apparatus of this invention. It is a wave form diagram for demonstrating the apparatus of FIG. It is a systematic diagram which shows one form of a part of apparatus of this invention. It is a frequency characteristic figure for demonstrating the apparatus of FIG. It is a systematic diagram for demonstrating the reproduction apparatus of a multichannel stereo.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... DVD player, 2 ... Decoder circuit, 3LF-3RB ... Adder circuit, 5 ... Overtone generation circuit, 6LF-6RB ... Level control circuit, 7LF-7RB ... Level detection circuit, 8 ... Discrimination control circuit, SPLF-SPRB ... Speaker , SPSW ... subwoofer, 100 ... distribution routine

Claims (2)

A multi-channel stereo audio reproduction device configured to perform audio reproduction by supplying audio signals of the above-mentioned channels corresponding to the arrangement positions of the speakers to a plurality of channels of speakers arranged around the listener,
f0: resonance frequency of the above speaker f1: when the fundamental wave component of a certain signal is multiplied, an upper limit value of the frequency that does not cause a sense of incongruity in the resulting multiplied wave component,
A harmonic generation circuit for generating a harmonic component having a double frequency by multiplying the low frequency component of the low frequency component for the subwoofer by a frequency that is included in the band f0 / 2 to f1 / 2.
The audio signal of each channel is supplied, and the audio signal of each channel is added and output at a predetermined ratio so that the harmonic signal generated by the harmonic generation circuit is distributed to each channel. A plurality of adder circuits;
A plurality of amplifiers for supplying the outputs of the adder circuits to the speakers of the channels ;
A plurality of level detection circuits for detecting the level of the audio signal of each of the channels and outputting a level detection signal indicating the detected level;
The harmonic components generated by the harmonic generation circuit are supplied, and a plurality of levels are output to the adding circuits by controlling the level of the harmonic components based on the level detection signals output from the level detection circuits. A control circuit;
The level detection signals are respectively supplied from the level detection circuits, the ratio of the level detection signals to the sum of the level detection signals is determined for each channel, and the determination signals indicating the determination results are respectively determined for the respective levels. A discrimination control circuit for outputting to the level control circuit ,
Each of the above level control circuits
Based on the discrimination signal for each of the channels supplied from the discrimination control circuit, the level of the harmonic component is controlled so that the harmonic signal generated by the harmonic generation circuit is weighted and distributed to each channel. And an audio playback device for outputting to each of the adder circuits . The discrimination control circuit is
Each level detection signal is compared with a predetermined specified value, and when the level of all the audio signals is smaller than the specified value, the harmonic signal generated by the harmonic generation circuit is equally distributed to each channel. When each level control circuit is set so as to be distributed to each other and the level of at least one or more audio signals is greater than the specified value, the level detection signal for the sum of the level detection signals for each channel The audio reproducing apparatus according to claim 1 , wherein each of the determination signals is output to each of the level control circuits.

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