This invention relates to array speaker systems in which a plurality of speaker units are arranged in an array.
Conventionally, array speaker systems in which a plurality of speakers are regularly arranged so as to reproduce sounds are known. In these array speaker systems, as a form of trouble due to the use of plural speakers, there occurs a phenomenon in which as reproduced audio frequencies become higher, so-called beam-like concentration of sound and comb-like distribution of sound (in which sound is spread in a comb-shape manner) emerge in sound emission characteristics, which vary in response to frequencies and which make it difficult to realize hearing of prescribed tone pitches outside of a sound emission center position, or in which audio frequency characteristics greatly vary in response to listening positions.
As shown in
In order to avoid the occurrence of the aforementioned phenomenon, a so-called Bessel array method, in which a string of regularly arranged speakers are driven with weights using a string of coefficients based on a first-order Bessel function so as to realize spherical sound emission characteristics, is known. In this method, a plurality of speaker units, which are linearly arranged with prescribed distances therebetween, are driven to emit sound signals, which are weighted by use of weight coefficients based on the first-order Bessel function represented by the following equation.
Similarly to
Incidentally, J−7(x) to J7(x) are used as weight coefficients adapted to speaker units, wherein when x=3.0, coefficients C1 to C15, which are used for multiplication with respect to signals driving fifteen speaker units, are calculated as follows:
It is obvious that through the comparison between
Japanese Examined Patent Application Publication No. H01-25480 discloses a speaker system adopting a simplified form of the aforementioned Bessel array.
When sound emitted from an array speaker is reflected on a wall surface and a ceiling so as to realize surround effect, characteristics of the array speaker in which emitted sound is easily subjected to beam-like concentration may work desirably. However, there is a problem in that the listening position is limited with respect to a tone-generation channel regarding sound emission in front of the listener.
It is an object of this invention to provide an array speaker system in which by effectively using characteristics of an array speaker, in which beam-like concentration of sound easily occurs, and the properties of a Bessel array, which realize spherical sound emission characteristics, both of the front-side sound and rear-side sound produced by the array speaker can be reproduced desirably.
An array speaker system of this invention is constituted by arraying a plurality of speaker units, each of which inputs a front-side channel signal for instructing generation of sound reproduced at a front side of a listener and a rear-side channel signal for instruction generation of sound reproduced at a rear side of the listener. Herein, speaker units are each driven by use of a front-side channel signal that is weighted using weight coefficients based on a Bessel function; and the speaker units are each driven by use of a rear-side channel signal that is subjected to prescribed delay processing so as to form a sound beam, which is reflected on a wall surface and a ceiling and then reaches the rear side of the listener.
The aforementioned array speaker system can be constituted by use of a first array speaker, which is arranged at the left side of a display, and a second array speaker, which is arranged at the right side of the display, for example.
With respect to the first array speaker arranged at the left side of the display, a left-channel signal and a center-channel signal are weighted using weight coefficients based on a Bessel function; and a surround left-channel signal is subjected to beam processing. With respect to the second array speaker arranged at the right side of the display, a right-channel signal and a center-channel signal are weighted using weight coefficients based on a Bessel function; and a surround right-channel signal is subjected to beam processing.
When the array speaker system is constituted by use of an array speaker arranged at the front side of a listener, front-side channel signals, i.e., a center-channel signal, a left-channel signal, and a right-channel signal, are respectively weighted using weight coefficients based on a Bessel function; and rear-side channel signals, i.e., a surround left-channel signal and a surround right-channel signal, are subjected to beam processing.
Furthermore, when the array speaker system is constituted by use of array speakers that are arranged in a matrix manner, speaker units are driven by use of signals, which instruct reproduction of sounds at setup locations of the array speakers and which are respectively weighted using weight coefficients based on a Bessel function. In addition, speaker units are driven by use of signals, which instruct reproduction of sounds at specific positions outside of setup locations of array speakers and which are subjected to delay processing so as to form sound beams reaching the specific positions.
As shown in
A Bessel array method in which the array speakers 1 and 2 are each driven with weights corresponding to weight coefficients based on a Bessel function is applied to the three channels lying in front of the listener 4, i.e., the aforementioned channels C, L, and R, whereby it is possible to realize spherical sound emission characteristics as shown in
With respect to the SL channel and the SR channel for the rear side of the listener 4, sound beams emitted from the array speakers 1 and 2 respectively are reflected on prescribed walls and ceiling so as to make it possible for the listener 4 to hear sound virtually emitted from the rear side. That is, the sound beam of the SR channel emitted from the first array speaker 1 is firstly directed to the left-side wall surface 5; then, it is reflected on the wall surface 5; next, it is reflected on the ceiling (not shown); furthermore, it is reflected on the rear-side wall surface 6; thereafter, it reaches the rear-left portion of the head of the listener 4. The sound beam of the SR channel emitted from the second array speaker 2 is firstly directed to the right-side wall surface 7; then, it is reflected on the wall surface 7, ceiling, and wall surface 6 in turn; thereafter, it reaches the rear-right portion of the head of the listener 4.
As described above, in the present embodiment, it is possible to realize spherical sound emission characteristics with respect to the three channels in front of the listener 4, i.e., the channels L, R, and C; hence, it is possible to realize natural audio reproduction without causing limitation to listening position. In addition, components of sound beams are effectively used with respect to the surround channels SL and SR regarding the rear side of the listener 4; hence, it is possible to realize audio reproduction at the rear side of the listener 4.
Next, a circuit constitution for driving the array speakers 1 and 2 will be described.
In
Reference numerals 17-11 to 17-mn designate adders that are respectively arranged for the speaker units 1-11 to 1-mn so as to add output signals of the weighting means 12-11 to 12-mn, output signals of the weighting means 14-11 to 14-mn, and output signals of the delay means 16-11 to 16-mn together. Output signals of the adders 17-11 to 17-mn are converted into analog signals in D/A converters (DAC) 18-11 to 18-mn; furthermore, they are amplified in power amplifiers 19-11 to 19-mn; thereafter, they are supplied to the speaker units 1-11 to 1-mn respectively.
As described above, addition signals that are produced by adding the C channel signals and L channel signals weighted based on the Bessel function to the SL channel signals applied with prescribed delay values are supplied to the speaker units 1-11 to 1-mn constituting the first array speaker 1 as its drive signals.
Illustration is not provided herein, but it is possible to provide amplifiers for adjusting gains of the signals of the respective channels with respect to the speaker units. That is, it is possible to additionally provide amplifiers for adjusting gains of the signals for the speaker units prior to the weighting means 12-11 to 12-mn, prior to the weighting means 14-11 to 14-mn, or prior to the delay means 16-11 to 16-mn.
In addition, the same circuit constitution as the circuit constitution of
In the circuit constitution of
It is described in conjunction with
It is possible to use the same weight coefficient for both the L-channel signal and the C-channel signal; alternatively, it is possible to use different weight coefficients using different parameters x1 and x2. In addition, it is possible to use weight coefficients, which are similarly determined, with respect to the second array speaker 2.
Delay values applied to the delay means 16-11 to 16-mn with respect to signals of the surround left channel (SL) will be described with reference to
In
An example in which a plurality of speaker units 1-1 to 1-n are arrayed in a one-dimension manner is described in conjunction with
In order for a sound beam emitted from the array speaker 1 or 2 to reach the wall surface 5 or 7 with a prescribed angle, it is preferable to set the number n of the speaker units in the columnar alignment to 5 or more.
As described above, in the present embodiment, sound beams emitted from the array speakers are reflected on the wall surfaces and ceiling so as to realize the surround channel sound that is transmitted to the listener at the rear side. That is, it is possible to effectively use characteristics of the array speaker in which sound is transformed into a beam.
The first embodiment describes the array speaker system constituted by the first array speaker arranged at the left side of the display 3 and the second array speaker 2 arranged at the right side of the display 3. This invention is not necessarily limited to an array speaker system having a divided arrangement of speakers.
In
In
Reference numerals 24-11 to 24-jk designate multipliers that are provided in connection with the speaker units 21-11 to 21-jk respectively so as to apply prescribed gains to the L-channel signals. In addition, reference numerals 25-11 to 25-jk designate weighting means for applying weight coefficients based on a Bessel function to the L-channel signals.
Reference numerals 26-11 to 26-jk designate multipliers that are provided in connection with the speaker units 21-11 to 21-jk respectively so as to apply prescribed gains to the R-channel signals. In addition, reference numerals 27-11 to 27-jk designate weighting means for applying weight coefficients based on a Bessel function to the R-channel signals.
Reference numerals 28-11 to 28-jk designate multipliers that are provided in connection with the speaker units 21-11 to 21-jk respectively so as to apply prescribed gains to the SL-channel signals. In addition, reference numerals 29-11 to 29-jk designate delay means that apply prescribed delay values to the speaker units 21-11 to 21-jk in order to form a sound beam in response to the SL-channel signals.
Reference numerals 30-11 to 30-jk designate multipliers that are provided in connection with the speaker units 21-11 to 21-jk respectively so as to apply prescribed gains to the SR-channel signals. In addition, reference numerals 31-11 to 31-jk designate delay means that apply prescribed delay values to the speaker units 21-11 to 21-jk in order to form a sound beam in response to the SR-channel signals.
Reference numerals 32-11 to 32-jk designate adders that add together output signals of the weighing means 23-11 to 23-jk regarding the C-channel signals, output signals of the weighting means 25-11 to 25-jk regarding the L-channel signals, output signals of the weighting means 27-11 to 27-jk regarding the R-channel signals, output signals of the delay means 29-11 to 29-jk regarding the SL-channel signals, and output signals of the delay means 31-11 to 31-jk regarding the SR-channel signals. Reference numerals 33-11 to 33-jk designate amplifiers that respectively amplify output signals of the adders 32-11 to 32-jk so as to supply them to the speaker units 21-11 to 21-jk.
In the array speaker system of the second embodiment having the aforementioned constitution, three-channel signals in front of the listener, i.e., C-channel signals, L-channel signals, and R-channel signals, are respectively weighted using weight coefficients based on a Bessel function, whereby the speaker units 21-11 to 21-jk emit sounds in a Bessel-array-like manner. In addition, with respect to surround signals at the rear side of the listener, i.e., SL-channel signals and SR-channel signals, the speaker units 21-11 to 21-jk emit desired sound beams.
In addition, the multipliers 22-11 to 22-jk, 24-11 to 24-jk, 26-11 to 26-jk, 28-11 to 28-jk, and 30-11 to 30-jk are provided to set up gains for the speaker units 21-11 to 21-jk with respect to signals of the C channel, L channel, R channel, SL channel, and SR channel. Herein, the multipliers 24-11 to 24-jk, which are provided to apply gains to the speaker units 21-11 to 21-jk with respect to the L-channel signals, increase gains for the speaker units arrayed at the left-half side but decrease gains for the speaker units arrayed at the right-half side within the speaker units arrayed in a two-dimensional manner, for example. In addition, the multipliers 26-11 to 26-jk, which are provided to apply gains to the speaker units 21-11 to 21 -jk with respect to the R-channel signals, increase gains for the speaker units arrayed at the right-half side but decrease gains for the speaker units arrayed at the left-half side within the speaker units arrayed in a two-dimensional manner, for example.
In the second embodiment compared with the first embodiment shown in
Incidentally, the aforementioned description is made with respect to the 5.1 channel surround system, which is an example of multi-channel reproduction; however, this invention is not necessarily so limited to and is similarly applicable to other multi-channel reproduction using 7.1 channels, for example.
Applied fields of this invention are not necessarily limited to multi-channel reproduction; hence, it is possible to perform audio reproduction using a Bessel array at the setup position of an array speaker and to perform audio reproduction using sound beams at another position.
Next, a third embodiment in which this invention is applied to an audio reproduction system other than one effecting multi-channel reproduction will be described with reference to
In
In the third embodiment, speaker units are driven by use of signals, which are weighted based on a Bessel function, at a position A entirely covering the whole space of a room in which the array speaker 41 is fixed to the ceiling 42. In addition, sound beams are emitted to focus on a certain position such as a comer B of the room other than the setup position of the array speaker 41 by use of delayed signals. Thus, by use of the array speaker 41, it is possible to emit prescribed sound throughout the entirety of the room; and it is possible to emit sound beams towards a specific position such as the comer B of the room, for example. In this case, it is possible to emit reproduced sounds towards the positions A and B by use of the same signal; alternatively, it is possible to emit sounds reproduced by use of different signals.
As described heretofore, the array speaker system of this invention has a variety of effects and technical features as follows:
Incidentally, this invention is not necessarily limited to the aforementioned embodiments; hence, this invention embraces all changes within the scope of the invention as defined in the appended claims.
Number | Date | Country | Kind |
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2003-156766 | Jun 2003 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP04/07911 | 6/1/2004 | WO | 11/29/2005 |