The present invention relates to an audio reproduction device which reproduces audio by a plurality of speakers.
In an on-vehicle audio reproduction device, a left speaker and a right speaker are mounted on the positions asymmetric with each other with respect to a listener. For example, at the driver's seat, the sound from the right speaker (stereo right signal) is large and the sound from the left speaker (stereo left signal) is small. In order to obtain good stereophonic feeling, it is necessary to equalize the balance of the sound pressure levels from the left and the right speakers. When the sound from the left speaker is made larger, by the amplifier, so as to equalize the balance of the left and right sound pressure levels at the driver's seat, the sound from the left speaker becomes still larger at the assistant driver's seat. Therefore, there is a demand of a technique of adjusting the balance of the sound pressure levels from the left and right speakers at both the driver's seat and the assistant driver's seat.
From this point of view, the Patent Reference-1 realizes approximately equal sound pressure levels at the driver's seat and the assistant driver's seat at each frequency band by utilizing the directivity of the speakers. However, the method of the Patent Reference-1 has the following problems.
The first problem is that the desired characteristic can be obtained only at the low frequency band equal to or larger than 3 kHz. The second problem is that the method cannot flexibly correspond to the change of the vehicle type and the speaker layout, because the method depends on the characteristics of the speakers.
Japanese Patent Application Laid-open under No. H05-161192
The above is one example of the problem to be solved by the present invention. It is an object of the present invention to provide an audio reproduction device which can reproduce sound with equal sound pressure levels at both the left and the right seats, which is effective even at a high frequency band and which can flexibly correspond to the change of the speaker layout.
The invention of claim 1 is an audio reproduction device connected to two speakers arranged in a sound field, comprising: an input means which receives an input signal of one channel; a delay means which delays the input signal; and an output means which outputs the input signal delayed by the delay means to one of the two speaker and outputs the input signal received by the input means to the other one of the two speakers, wherein the delay means gives, to the input signal, a delay of different delay amount to each of a plurality of frequency bands.
The invention of claim 7 is an audio reproduction device connected to two pairs of speakers arranged in a sound field, comprising: an input means which receives the input signals of two channels; a delay means which delays the input signals of two channels, respectively; and an output means which outputs the input signal delayed by the delay means to one of the two speaker and outputs the input signal received by the input means to the other one of the two speakers, for the respective pairs of speakers, wherein the delay means gives, to the input signal, a delay of different delay amount to each of a plurality of frequency bands that the input signal has.
According to one aspect of the present invention, there is provided an audio reproduction device connected to two speakers arranged in a sound field, comprising: an input means which receives an input signal of one channel; a delay means which delays the input signal; and an output means which outputs the input signal delayed by the delay means to one of the two speaker and outputs the input signal received by the input means to the other one of the two speakers, wherein the delay means gives, to the input signal, a delay of different delay amount to each of a plurality of frequency bands.
The above audio reproduction device reproduces the signal of one channel from two speakers in a sound field. The input signal of one channel is delayed by the delay means. The delay means delays the input signal by the different delay amount for each of the plurality of frequency band. The signal delayed by the delay means is outputted to one of the two speakers, and the input signal is outputted to the other of the two speakers as it is.
In one mode of the above audio reproduction device, the delay means delays the input signal such that a difference between a sound pressure at one listening position in the sound field and a sound pressure at another listening position becomes zero, for audio outputted from the two speakers.
In another mode of the above audio reproduction device, the delay means delays the input signal such that a difference between a sound pressure at one listening position in the sound field and a sound pressure at another listening position becomes maximum, for audio outputted from the two speakers.
In a preferred example, the delay means sets the delay amount larger for the frequency band whose frequency is higher. In another preferred example, the one of the two speakers is a speaker which is near to the listening position in the sound field and the other one of the two speakers is a speaker which is farther from the listening position.
In another preferred example, the delay means comprises: a frequency band dividing section which divides the input signal to the plurality of frequency bands; and a delaying section which gives the delay to the signals of the plurality of frequency bands divided by the frequency dividing section.
According to another aspect of the present invention, there is provided an audio reproduction device connected to two pairs of speakers arranged in a sound field, comprising: an input means which receives the input signals of two channels; a delay means which delays the input signals of two channels, respectively; and an output means which outputs the input signal delayed by the delay means to one of the two speaker and outputs the input signal received by the input means to the other one of the two speakers, for the respective pairs of speakers, wherein the delay means gives, to the input signal, a delay of different delay amount to each of a plurality of frequency bands that the input signal has.
The above audio reproduction device reproduces the two-channel signal by two pairs of speakers. Namely, one-channel signal is reproduced by one pair of speakers, and other one-channel signal is reproduced by the other pair of speakers. For each channel, the one-channel input signal is delayed by the delay means. The delay means delays the input signal by the delay amount different for each of the plurality of frequency bands. For each channel, the signal delayed by the delay means is outputted to the one of the two speakers, and the input signal is outputted to the other of the two speakers as it is.
In one mode of the above audio reproduction device, the delay means delays the input signal such that a difference between a sound pressure at one listening position in the sound field and a sound pressure at another listening position becomes zero, for audio outputted from the two pairs of speakers, respectively.
In another mode of the above audio reproduction device, the delay means delays the input signal such that a difference between a sound pressure at one listening position in the sound field and a sound pressure at another listening position becomes maximum, for audio outputted from the two pairs of speakers, respectively.
Preferred embodiments of the present invention will be described below with reference to the attached drawings.
As shown, the driver's seat exists on the segment L1 perpendicular to the segment which connects the front right speaker FR and the rear right speaker RR. The assistant driver's seat exists on the segment L2 perpendicular to the segment which connects the front left speaker FL and the rear left speaker RL. In this embodiment, the segment L1 and the segment L2 are on an extension line, and therefore the driver's seat and the assistant driver's seat are on an identical line. Namely, both the driver's seat and the assistant driver's seat are on the segment L1 perpendicular to the segment which connects two right speakers and also on the segment L2 perpendicular to the segment which connects two left speakers. The driver's seat and the assistant driver's seat correspond to the listening position in the present invention.
The signals of the respective frequency bands thus divided are transferred to the delay unit 9R. The delay unit 9R gives the delays of different delay amount to the signals of the respective frequency bands, and then outputs them to the mixer 6R. The mixer 6R synthesizes the signals to which different delays are given for the respective frequency bands by the delay unit 9R, and outputs the signal to the front right speaker FR.
The configuration of the 1ch processing unit 7L for the left speakers is basically the same as the 1ch processing unit 7R for the right speakers. Namely, the 1ch processing unit 7L divides the input signal 5L into a predetermined plural frequency bands, and gives the different delays for the respective frequency bands to output to the front left speaker FL. At the same time, the 1ch processing unit 7L outputs the input signal 5L to the rear left speaker RL as it is.
Meanwhile,
Next,
p(f)=a*log10(f)+b (1)
wherein: a=13.8, b=−36.5, p:phase [radian], f:frequency[Hz].
As described above, by determining the delay amount of each frequency band by the delay unit 9R in the 1ch processing unit 7R in accordance with the characteristic between the frequency and the delay amount shown in
In the above description, the characteristics shown in
While the above description is directed to the right speakers, the delay control processing can be performed for the left speakers in the same manner, so as to set the delay amount for each frequency band. Namely, for the two left speakers, the sound pressure distribution at the driver's seat and the sound pressure distribution at the assistant driver's seat are measured, the sound pressure distribution of (Driver's Seat-Assistant Driver's Seat) is generated by the subtraction, and the optimum delay amount with which the sound pressure difference becomes zero is obtained on the distribution. Then, the delay amount for each frequency band can be determined based on the optimum delay amount.
Since the method of this embodiment adjusts only the time of the front speaker, the sound from the front speaker further delays, and reaches the rear seat of the vehicle after being attenuated by the amount corresponding to the distance. Therefore, the sound interference occurring at the front seats (the driver's seat and the assistant driver's seat) hardly occur. As a result, the person sitting on the rear seat can enjoy the stereophonic reproduction by the sound from the rear speakers, to which no processing is applied. In addition, since the method of this embodiment does not electrically vary the frequency characteristic like the equalizer, it is possible to enjoy the high quality music at any seat in the vehicle.
In the second embodiment, the speaker layout is the same as that shown in
In the above-described first embodiment, the delay amount is controlled such that the sound pressure levels at the driver's seat and the assistant driver's seat becomes equal to each other. In contrast, in the second embodiment, the delay amount is controlled such that the difference of the sound pressure levels at the driver's seat and the assistant driver's seat becomes maximum.
p(f)=a*log10(f)+b (2)
wherein a=9.3 and b=−20.0
By determining the delay amount of each frequency band according to
Returning to
p(f)=a*log10(f)+b (2)
wherein a=13.0 and b=−35.0.
By determining the delay amount of each frequency band according to
As described above, in the second embodiment, by determining the delay amounts such that the sound pressure level difference between the driver's seat and the assistant driver's seat becomes maximum, the sound pressure level difference of the sound outputted from the left and right speakers can be maximum at the driver's seat or the assistant driver's seat. Thus, for example, by making the sound pressure level difference from two right speakers becomes maximum at the driver's seat, it is possible to make the guide voice of the car navigation be audible only at the driver's seat.
The present invention provides a device which equalizes the sound pressures at two seats arranged on the segment perpendicular to the segment which connects two speakers. Therefore, not only the above-described embodiments, the sound pressures can be equalized at two seats arranged in front and behind, by using two front speakers. This is effective in the case that monophonic signal or a center signal of 5.1ch surround signals is reproduced by two front speakers.
This invention can be used for a sound field correction of an on-vehicle audio apparatus.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP2008/059736 | 5/27/2008 | WO | 00 | 11/8/2010 |