1. Field of the Invention
The present invention relates to a sound signal playback machine and method thereof for playing back multichannel sounds.
2. Description of the Related Art
Concerning the sound signal playback machine for playing back multichannel sounds, for example, a sound signal playback machine to realize 5.1 surround playback is well known.
In this connection, the above conventional sound signal playback machine is designed so that the frequency response can be flat when signals on the low frequency side and those on the high frequency side are electrically synthesized with each other. Further, in the above conventional sound signal playback machine, it is necessary to use a filter of the high order so that the band width, in which the frequency response on the low frequency side and that on the high frequency side cross each other, can be reduced. Accordingly, the following problems may be encountered. The frequency response of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, are flat as shown in
The present invention has been accomplished in view of the above circumstances. It is an object of the present invention to provide a sound signal playback machine and method thereof capable of making a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are synthesized with each other, flat so that sounds of low frequency can be faithfully played back and a nuance of sounds of a musical instrument of low frequency can be improved.
In order to accomplish the above object, first, the present invention provides a sound signal playback machine comprising: a high frequency pass filter for extracting a predetermined high frequency component from a sound signal in a main channel; a first speaker for playing back the high frequency component extracted by the high frequency pass filter; a low frequency pass filter for extracting a predetermined low frequency component from the sound signal in the main channel; a signal adder for outputting an addition signal in which the low frequency component extracted by the low frequency pass filter is added to a sound signal in a channel exclusively used for a low frequency band; and a second speaker for playing back the addition signal outputted from the signal adder, wherein the degree of the low frequency pass filter is set higher than that of the high frequency pass filter, the sound signal playback machine further comprising a phase matching means for matching the phase of the high frequency component extracted by the high frequency pass filter with the phase of the low frequency component extracted by the low frequency pass filter. According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Secondly, the present invention provides a sound signal playback machine according to the above item 1, wherein the phase matching means is a delay circuit for delaying the high frequency component extracted by the high frequency pass filter. According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Thirdly, the present invention provides a sound signal playback machine according to the above item 2, wherein delay time T1 (sec) of the delay circuit is set at a value calculated by the equation of
T1=(φ1−φ2+π·n)/(2πFc)
Fourthly, the present invention provides a sound signal playback machine according to the above item 1, wherein the phase matching means is to set the first speaker by moving it in a direction so that the first speaker can be separated from a listener. According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Fifthly, the present invention provides a sound signal playback machine according to the above item 1, wherein the phase matching means is to set the second speaker by moving it in a direction so that the second speaker can be approached to a listener, and the phase matching means is also a delay circuit for delaying the addition signal outputted from the signal adder. According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Sixthly, the present invention provides a sound signal playback machine according to one of the above items 1 to 5, further comprising an auxiliary phase matching means for matching the phase of the low frequency component extracted by the low frequency pass filter with the phase of the sound signal in the channel exclusively used for the low frequency band. According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat. Even when sound signals in the channel exclusively used for the low frequency band and sound signals in the main channel are correlated with each other, there is no possibility that the group delay is increased in the low frequency band.
Seventhly, the present invention provides a sound signal playback machine according to the above item 6, wherein the auxiliary phase matching means is a delay circuit for delaying the sound signal in the channel exclusively used for the low frequency band. According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat. Even when sound signals in the channel exclusively used for the low frequency band and sound signals in the main channel are correlated with each other, there is no possibility that the group delay is increased in the low frequency band.
Eighthly, the present invention provides a sound signal playback machine according to the above item 7, wherein delay time T2 (sec) of the delay circuit is set at a value calculated by the equation of
T2=(φ1+π·n)/(2π·Fc)
Ninthly, the present invention provides a sound signal playback machine according to one of the above items 1 to 5, further comprising a phase inversion circuit for inverting a phase of the low frequency component extracted by the low frequency pass filter when a difference between the phase of the low frequency component extracted by the low frequency pass filter and the phase of the sound signal in the channel exclusively used for the low frequency is π (rad). According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Tenthly, the present invention provides a sound signal playback method comprising the steps of: extracting a predetermined high frequency component from a sound signal in a main channel by a high frequency pass filter; playing back the high frequency component, which has been extracted by the high frequency pass filter, by a first speaker; extracting a predetermined low frequency component from the sound signal in the main channel by a low frequency pass filter; adding the low frequency component extracted by the low frequency pass filter to a sound signal in the channel exclusively used for the low frequency by a signal adder and outputting an addition signal; and playing back the addition signal, which has been outputted from the signal adder, by a second speaker, wherein the degree of the low frequency pass filter is set higher than that of the high frequency pass filter, and the phase of the high frequency component extracted by the high frequency pass filter and the phase of the low frequency component extracted by the low frequency pass filter are matched with each other. According to the sound signal playback method described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Eleventhly, the present invention provides a sound signal playback method according to the above item 10, wherein the phase of the high frequency component extracted by the high frequency pass filter and the phase of the low frequency component extracted by the low frequency pass filter are matched with each other when the high frequency component extracted by high frequency pass filter is delayed by the delay circuit. According to the sound signal playback method described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Twelfthly, the present invention provides a sound signal playback method according to the above item 11, wherein delay time T1 (sec) of the delay circuit is set at a value calculated by the equation of
T1=(φ1−φ2+π·n)/(2π·Fc)
Thirteenthly, the present invention provides a sound signal playback method according to the above item 10, wherein the phase of the high frequency component extracted by the high frequency pass filter and the phase of the low frequency component extracted by the low frequency pass filter are matched with each other when the first speaker is arranged by moving so that it can be separated from a listener. According to the sound signal playback method described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Fourteenthly, the present invention provides a sound signal playback method according to the above item 10, wherein the phase of the high frequency component extracted by the high frequency pass filter and the phase of the low frequency component extracted by the low frequency pass filter are matched with each other when the second speaker is arranged by moving so that it can be separated from a listener and the addition signal outputted from the signal adder is delayed by the delay circuit. According to the sound signal playback method described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Fifteenthly, the present invention provides a sound signal playback method according to one of the above items 10 to 14, wherein the phase of the low frequency component extracted by the low frequency pass filter and the phase of the sound signal in the channel exclusively used for the low frequency band are matched with each other. According to the sound signal playback method described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat. Even when sound signals in the channel exclusively used for the low frequency band and sound signals in the main channel are correlated with each other, there is no possibility that the group delay is increased in the low frequency band.
Sixteenthly, the present invention provides a sound signal playback method according to the above item 15, wherein the phase of the low frequency component extracted by the low frequency pass filter and the phase of the sound signal in the channel exclusively used for the low frequency band are matched with each other by delaying the sound signal in the channel exclusively used for the low frequency band by the delay circuit. According to the sound signal playback method described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat. Even when sound signals in the channel exclusively used for the low frequency band and sound signals in the main channel are correlated with each other, there is no possibility that the group delay is increased in the low frequency band.
Seventeenthly, the present invention provides a sound signal playback method according to the above item 16, wherein delay time T2 (sec) of the delay circuit is set at a value calculated by the equation of
T2=(φ1+π·n)/(2π·Fc)
Eighteenthly, the present invention provides a sound signal playback method according to one of the above items 10 to 14, wherein the phase of the low frequency component extracted by the low frequency pass filter is inverted by the phase inversion circuit when a difference between the phase of the low frequency component extracted by the low frequency pass filter and the phase of the sound signal in the channel exclusively used for the low frequency is π (rad). According to the sound signal playback method described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Referring to the accompanying drawings, embodiments of the present invention will be explained in detail as follows.
First Embodiment
In this case, the speakers 61 to 65 compose a speaker system for playing back sounds of middle low frequency and higher frequency than that. In general, they are referred to as a satellite speaker system. The speaker 66 is a speaker system for playing back sounds of low frequency. In general, the speaker 66 is referred to as a sub-woofer. These speakers 61 to 66 are arranged, for example, as shown in
HPF 21 to 25 respectively extract a predetermined high frequency component from the digitized sound signal of the channel (main channel) except for channel LFE. LPF 71 to 75 extract a predetermined low frequency component from the digitized sound signal in the same manner. When the degree of HPF 21 to 25 is N1 and the degree of LPF 71 to 75 is N2, it is set that N2>N1, that is, it is set that the degree of LPF 71 to 75 is higher than the degree of HPF 21 to 25. In this connection, in the sound signal playback machine of the first embodiment, the degree of LPF 71 to 75 is set at “4” (N2=4), and the degree of HPF 21 to 25 is set at “2” (N1=2).
The delay circuits 31 to 35 are provided as a phase matching means for matching a phase of the high frequency component extracted by HPF 21 to 25 with a phase of the low frequency component extracted by LPF 71 to 75. Delay time T1 (sec) of each delay circuit 31 to 35 is set at a value calculated by the equation of
T1=(φ1−φ2+π·n)/(2π·Fc)
In this connection, in the sound signal playback machine of the first embodiment, the delay time of each delay circuit 31 to 35 is set at 5 msec (T1=5 msec).
The delay circuit 84 is provided as an auxiliary phase matching means for matching the phase of the low frequency component extracted by LPF 71 to 75 with the phase of the digitized sound signal in LFE channel in the case where sound signals SL to SC in the main channel and sound signal SLFE in LFE channel are correlated with each other. Delay time T2 (sec) of this delay circuit 84 is set at a value calculated by the equation of
T2=(φ1+π·n)/(2π·Fc)
The phase inversion circuit 82 is controlled so that a phase of a signal outputted from the signal adder 81 can be inverted when a phase difference between the signal outputted from the signal adder 81 and the signal outputted from the delay circuit 84 is π (rad) (180°). That is, when n in the equation to calculate delay time T1 is represented by n=. . . 3, −1, 1, 3 . . . , the phase inversion circuit 82 conducts a phase inversion motion. When n in the equation to calculate delay time T1 is represented by n=. . . −4, 2, 0, 2, 4 . . . , the phase inversion circuit 82 does not conduct a phase inversion motion. In this connection, the value of n is determined by HPF and LPF to be used. Therefore, when n=. . . −4, −2, 0, 2, 4 . . . , the phase inversion circuit 82 may not be provided.
As described above, in the sound signal playback machine of the first embodiment, the degree of LPF 71 to 75 is set higher than the degree of HPF 21 to 25, and the delay circuits 31 to 35 are provided as a phase matching means. Therefore, the phase characteristic of a signal, which is obtained when the signal on the low frequency side and the signal on the high frequency side are electrically synthesized with each other, becomes substantially flat as shown in
Second Embodiment
As described above, in the sound signal playback machine of the second embodiment, the degree of LPF 71 to 75 is set higher than the degree of HPF 21 to 25, and the speakers 61 to 65 used for the main channel are provided as a phase matching means being respectively moved in a direction so that they can be separate from the listener 91. Therefore, the sound signal playback machine of the second embodiment can provide the same effect as that of the sound signal playback machine of the first embodiment described before.
Third Embodiment
As described above, in the sound signal playback machine of the third embodiment, the degree of LPF 71 to 75 is set higher than the degree of HPF 21 to 25, and the speaker 66 used for the main channel is provided as a phase matching means being respectively moved in a direction so that it can be approached to the listener 91, and the delay circuit 85 is arranged at the rear of the signal adder 83. Therefore, the sound signal playback machine of the third embodiment can provide the same effect as that of the sound signal playback machine of the first embodiment.
Fourth Embodiment
In this case, the speakers 61 to 66, HPF 21 to 25, LPF 71 to 75, delay circuits 31 to 35, phase inversion circuit 82 and delay circuit 84 are the same as those of the first embodiment described before. Therefore, the explanations are omitted here.
Each delay circuit 31a to 35a fulfills a function of adjusting a speaker distance. In order to adjust a distance from the listener 91 to each speaker 61 to 65 used for the main channel shown in
As described above, in the sound signal playback machine of the fourth embodiment, the degree of LPF 71 to 75 is set higher than the degree of HPF 21 to 25, and the delay circuits 31 to 35 are provided as a phase matching means. Therefore, the same effect as that of the sound signal playback machine of the first embodiment can be provided.
In the first to the fourth embodiment, a phase converting circuit for conducting fine adjustment on the group delay may be arranged at the front stage of each of A/D converters 11 to 15. Signal processing may be conducted not by digital processing but by analogue processing.
As can be seen from the above explanations, according to the present invention, the degree of the low frequency pass filter is set higher than the degree of the high-frequency-pass-filter, and the phase of the high frequency component extracted by the high frequency pass filter and the phase of the low frequency component extracted by the low frequency pass filter are matched to each other. Therefore, the group delay characteristic of the signal, which is obtained when the signal on the low frequency band side and the signal on the high frequency band side are electrically synthesized with each other, becomes substantially flat. Accordingly, sounds of low frequency can be faithfully played back and a nuance of sounds of a musical instrument of low frequency can be improved. Therefore, sounds can be excellently played back by means of multichannel playback.
Number | Date | Country | Kind |
---|---|---|---|
P2001-176399 | Jun 2001 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
4589135 | Baker | May 1986 | A |
5230022 | Sakata | Jul 1993 | A |
5325435 | Date et al. | Jun 1994 | A |
5377274 | Meyer et al. | Dec 1994 | A |
5642427 | Katz et al. | Jun 1997 | A |
5642429 | Janssen | Jun 1997 | A |
5751817 | Brungart | May 1998 | A |
5930374 | Werrbach et al. | Jul 1999 | A |
6169812 | Miller | Jan 2001 | B1 |
6606388 | Townsend et al. | Aug 2003 | B1 |
7043032 | Jeffs et al. | May 2006 | B1 |
7277551 | Miura et al. | Oct 2007 | B2 |
20040032955 | Hashimoto et al. | Feb 2004 | A1 |
Number | Date | Country |
---|---|---|
195 33 946 | Jun 1996 | DE |
2-30699 | Feb 1990 | JP |
06-233377 | Aug 1994 | JP |
07-099700 | Apr 1995 | JP |
09-065497 | Mar 1997 | JP |
11-041699 | Feb 1999 | JP |
2000-217197 | Aug 2000 | JP |
Number | Date | Country | |
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Parent | 10164411 | Jun 2002 | US |
Child | 11546485 | US |