Apparatus and method for localizing sound image

Abstract: The present invention includes producing a first processed signal which localizes sound image at a first localization position and a second processed signal which localizes sound image at a second localization position; multiplying one of the first and the second processed signals by a coefficient k which varies in the range of 0 to 1; multiplying the other signal by a coefficient 1-k; and adding the processed signal multiplied by the coefficient k and the processed signal multiplied by the coefficient 1-k. When the predetermined position is located away at an angle  in a circumferential direction from the front of the listener, the first localization position is in the vicinity of the predetermined position and located away at an angle  1 in a circumferential direction from the front of the listener wherein  1 < , and the second localization position is in the vicinity of the predetermined position and located away at an angle  2 in a circumferential direction from the front of the listener wherein  2 > .

Description: The present invention relates to an apparatus and a method of localizing a sound image. Conventionally, a home television (TV) set capable of performing a stereophonic audio reproduction includes a pair of speakers (i.e., a left speaker and a right speaker). However, since such a TV set has a limited width for installing the speakers therein, it is not possible to enjoy stereophonic audio reproduction at satisfactory level. Furthermore, if such a TV set employs a "surround system", it is often difficult to provide surround speakers. In such a case, audio signals are subjected to a sound image localisation treatment (e.g., by using a head-related transfer function (HRTF)) and the treated signals are supplied to the speakers, so as to localise the sound image (i.e., virtual speakers) at positions where speakers are not actually arranged. The virtual speakers make a listener feel that the distance between the actually arranged speakers is wider, or feel that the reproduced sound is coming from the side or rear even though actually only two frontal speakers are arranged in front of the listener. Generally, in the case of a moving sound image, it is relatively easy to localise the sound image at a predetermined position although it depends on a listener. In contrast, in the case of a static sound image, it is difficult to localise the sound image at a predetermined position. In order to overcome the above-mentioned problem, a technique making a listener recognise a sound image at a predetermined position has been proposed. When the predetermined position is located at an angle  in a circumferential direction away from the front of the listener, the technique includes producing (i) a first processed signal for localising the sound image at a first localisation position located at an angle  1 in a circumferential direction away from the front of the listener wherein  1 < , and (ii) a second processed signal for localising the sound image at a second localisation position located at an angle  2 in the circumferential direction away from the front of the listener wherein  2 > ; and alternately supplying the first and the second processed signals to the speakers, so as to alternately localise the sound image at the first and the second localisation positions for making the listener recognise the sound image at the predetermined position. However, such a technique provides the listener with a quite unnatural feeling of hearing due to the regularity of the alternate sound image localisation around the predetermined position. As described above, an apparatus and a method of localising a sound image which provide a natural feeling of hearing is eagerly demanded. The method of the present invention, like a method known previously from Japanese Laid Open Patent Application JP-A-04030700 and Patent Abstracts of Japan Vol. 016 No. 200 (E-7201) 13 th May 1992, includes the following steps of providing a left speaker and a right speaker in front of a listener; subjecting an audio signal to a sound image localisation treatment by producing a first processed signal which localises the sound image at a first localisation position and a second processed signal which localises the sound image at a second localisation position; multiplying one of the first and the second processed signals by a coefficient k which varies in a range of 0 to 1; multiplying the other one of the first and the second processed signals by a coefficient 1-k; and adding the processed signal multiplied by the coefficient k and the process signal multiplied by the coefficient 1-k; and supplying the processed signal to the left and the right speakers, so as to localise the sound image at a predetermined position; wherein, when the predetermined position is located at an angle  in a circumferential direction away from the front of the listener, the first localisation position is in the vicinity of the predetermined position and located at an angle  1 in the circumferential direction away from the front of the listener wherein  1 < , and the second localisation position is in the vicinity of the predetermined position and located at an angle  2 in the circumferential direction away from the front of the listener wherein  2 > . The method aforesaid is, in accordance with the present invention, characterised in that the step of multiplying by the coefficient k is performed using as the coefficient a coefficient which varies in the range of 0 to 1 at random. In one embodiment of the invention, a spectrum of the coefficient k has 1/f characteristics. In another embodiment of the invention, a production of the coefficient k includes outputting a random signal having rectangular pulse shape, height of 1, and random pulse width and pitch, and integrating the random signal in an integration circuit. In still another embodiment of the invention, a production of the coefficient k includes squaring the audio signal by a squaring circuit, and processing the squared signal through a low pass filter. In still another embodiment of the invention, the audio signal is a 2-channel stereophonic signal, and a signal for producing the coefficient is selected from a signal of one of the channels, an added signal of the both channel, or a differential signal of the both channel. According to another aspect of the present invention, there is provided an apparatus for localising a sound image of the kind, such as known from JP-A-04030700, which includes: left and right speakers to be provided in front of a listener; a means for subjecting an audio signal to a sound image localisation treatment comprised of a means for producing a first processed signal which localises the sound image at a first localisation position, and a means for producing a second processed signal which localises sound image at a second localisation position; a means for producing a coefficient k which varies in the range of 0 to 1; a means for multiplying one of the first and the second processed signals by the coefficient k; a means for multiplying the other signal by a coefficient 1-k; and a means for adding the processed signal multiplied by the coefficient k and the processed signal multiplied by the coefficient 1-k and supplying the added signal to the left and the right speakers so as to localise the sound image at a predetermined position; wherein, when the predetermined position is located at an angle  in a circumferential direction away from the front of the listener, the first vocalisation position is in the vicinity of the predetermined position and located at an angle  1 in the circumferential directionaway from the front of the listener wherein  1 < , and the second localisation position is in the vicinity of the predetermined position and located at an angle  2 in the circumferential direction from the front of the listener wherein  2 > . The apparatus aforesaid is, in accordance with the present invention, characterised in that the means for producing the coefficient k is a means (PR, SC1, SK, L; SE, SQ ,SC2, LPF) that produces, as the coefficient k, a coefficient which varies in the range of 0 to 1 at random. In accordance with a further aspect of the present invention there is provided an audio signal processor as defined in claim 7 of the claims appended hereto. Thus, the invention described herein makes possible the advantages of: (1) providing an apparatus for localising a sound image which provides a natural feeling of hearing; and (2) a method of localising a sound image which provides a natural feeling of hearing. These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. In the accompanying drawings: Figure 1 is a block diagram illustrating an embodiment of an apparatus for localizing a sound image according to the present invention; Figure 2 is a configuration diagram illustrating a localization treatment of a sound image using an apparatus of Figure 1 ; Figure 3 is a block diagram illustrating an example of a first and a second signal processing means of Figure 1 ; Figure 4 is a block diagram illustrating another example of a first and a second signal processing means of Figure 1 ; Figure 5 is a block diagram illustrating an example of a means for producing coefficient k of Figure 1 ; Figures 6A shows an output from a random signal generator of Figure 5 ; Figures 6B shows an output from an integration circuit of Figure 5 ; Figure 7 is a block diagram illustrating another example of a means for producing coefficient k of Figure 1; Figure 8A shows an output from a signal-selecting circuit of Figure 7; Figure 8B shows an output from a squaring circuit of Figure 7; Figure 8C shows an output from a low pass filter of Figure 7; Figure 9 is a schematic diagram illustrating a relationship among  1 ,  2 and  according to the present invention. A preferred embodiment of the present invention swill now be described. The description that follows is given by way of example only. Referring to Figures 1 to 9, a preferred embodiment according to the present invention will be described. Figure 1 is a block diagram illustrating an apparatus according to this embodiment. The sound image localisation apparatus (the virtual speaker treatment apparatus) includes first and second input terminals 1 and 2 to which an audio signal is input, a first output terminal 3 connected to a left speaker SPL and a second output terminal 4 connected to a right speaker SPR. Although a 2-channel stereophonic signal is exemplarily shown as an audio signal in Figure 1, the audio signal instead may be a monophonic signal. Figure 2 shows an arrangement of the speakers SPL and SPR. As shown in Figure 2, a pair of speakers (i.e., a left speaker SPL and a right speaker SPR ) are provided in front of a listener M . As shown in Figure 9 , the sound image localization apparatus makes a listener M recognize a sound image at the predetermined position P. Here, the position P is located away at an angle  in a circumferential direction (i.e., counter-clockwise) from the front F of the listener M , this embodiment of the present invention includes (1) localizing sound image (a virtual speaker) at a first localization a position P1 which is in the vicinity of the predetermined position P and located at an angle  1 in the circumferential direction away from the front F of the listener wherein  1 < ; and (2) localizing a sound image (a virtual speaker) at a second localization position P2 which is in the vicinity of the predetermined position P and located at an angle  2 in the circumferential direction away from the front F of the listener wherein  2 > . As shown in Figure 9 also, when the position P is located at an angle - in another circumferential direction (i.e., clockwise) away from the front F of the listener, this embodiment of the present invention includes (1) localizing a sound image (a virtual speaker) at a first localization position P1 which is in the vicinity of the predetermined position P and located at an angle - 1 in the circumferential direction away from the front F of the listener; and (2) localizing sound image (a virtual speaker) at a second localization position P2 which is in the vicinity of the predetermined position P and located at an angle -  2 in the circumferential direction away from the front F of the listener. The difference between  and  1 and the difference between  and  2 may be the same or different. The difference between  and  1 or between  and  2 may be any suitable amount of angle, and typically, it may be about 30 degrees or less. The sound image localization apparatus includes a first signal-processing means (a first virtual speaker treatment means) 11 and a second signal-processing means (a second virtual speaker treatment means) 12 . The first and the second means are connected to input terminals 1 and 2 . The first signal-processing means 11 is used for localising the sound image at a first localization position P1 and outputs a first L-signal for a left speaker SPL and a first R-signal for a right speaker SPR . The second signal-processing means 12 is used for localizing the sound image at a second localisation position P2 and outputs a second L-signal for a left speaker SPL and a second R-signal for a right speaker SPR . .The first and the second signal-processing means 11 and 12 are typically signal-processing circuits. For example, the means 11 and 12 may be a "lattice type" filter or a "shuffler type" filter. More specifically, the sound image localization apparatus may include a pair of lattice type filters or a pair of shuffler type filters. A method for localizing a sound image, which provides a listener with a "surround" feeling by using such filters, have already been proposed by the present inventors. As shown in Figure 3, a lattice type filter includes: (i) a first L-filtering portion (a first L-signal-processing portion) F1L , which is connected to a first input terminal 1 and outputs an output signal for a left speaker SPL; (ii) a first R-filtering portion (a first R-signal-processing portion) F1R, which is connected td a first input terminal 1 and outputs an output signal for a right speaker SPR; (iii) a second L-filtering portion (a second L-signal-processing portion) F2L, which is connected to a second input terminal 2 and outputs an output signal for a left speaker SPL; (iv) a second R-filtering portion (a second R-signal-processing portion) F2R, which is connected to a second input terminal 2 and outputs an output signal for a right speaker SPR; (v) an adding means M8 which adds output signals of a first and a second L-filtering portions F1L and F2L so as to produce a first L-processed signal or a second L-processed signal; (vi) an adding means M9 which adds output signals of a first and a second R-filtering portions F1R and F2R so as to produce a first R-processed signal or a second R-processed signal. A transfer function of a first L-filtering portion F1L, a first R-filtering portion F1R, a second L-filtering portion F2L and a second R-filtering portion F2R is defined as H 11, H 12 , H 21 and H 22 , respectively. The details of the transfer function are described below. For example, in the case of localizing the sound image (i.e., virtual left and right speakers) ZL and ZR at positions sideward or rearward of the listener M as shown in Figure 2 , transfer functions H 11 , H 12 , H 21 and H 22 of the first L-filtering portion F1L, the first R-filtering portion F1R, the second L-filtering portion F2L and the second R-filtering portion F2R are obtained by using head-related transfer functions h LL , h LR , h RL , h RR , h L'L , h L'R , h R'L and h R'R . Here, h LL is a head-related transfer function from the left speaker SPL to a left ear of the listener M, and h LR is a head-related transfer function from the left speaker SPL to a right ear of the listener M ; h RL is a head-related transfer function from the right speaker SPR to a left ear of the listener M, and h RR is a head-related transfer function from the right speaker SPR to a right ear of the listener M ; h L'L is a head-related transfer function from the virtual left speaker ZL to a left ear of the listener M , and h L'R is a head-related transfer function from the virtual left speaker ZL to a right ear of the listener M ; and h R'L is a head-related transfer function from the virtual right speaker ZR to a left ear of the listener M, and h R'R is a head-related transfer function from the virtual right speaker ZR to a right ear of the listener M . The calculation procedure is as follows. Initially, defining as indicated below a matrix [h] of the head-related transfer functions from the speakers SPL and SPR to the ears of the listener M, a matrix [h'] of the head-related transfer functions from the virtual speakers ZL and ZR to the ears of the listener M, and a matrix [H] of the lattice type filter. According to the relationship shown in Figures 2 and 3, the following equation is satisfied: [h'] = [h] [H] If |h|≠0, then the below-indicated equation (5) can be derived from equation (4): [H] = [h] -1 [h'] Transfer functions H 11 , H 12 , H 21 and H 22 of the first L-filtering portion F1L , the first R-filtering portion F1R , the second L-filtering portion F2L and the second R-filtering portion F2R can be obtained by using equation (5) as follows: H 11 = (h RR h L'L - h RL h L'R ) / (h LL h RR - h LR h RL ) H 12 = (h LL h L'R - h LR h L'L ) / (h LL h RR - h LR h RL ) H 21 = (h RR h R'L - h RL h R'R ) / (h LL h RR - h LR h RL ) H 22 = (h LL h R'R - h LR h R'L ) / (h LL h RR - h LR h RL ) Alternatively, as shown in Figure 4, a shuffler type filter includes: a first filtering portion (a first signal-processing portion) F1 ; a second filtering portion (a second signal-processing portion) F2 ; an adding means M1 which adds audio signals input to the first and second terminals 1 and 2 and inputs the added signal to the first filtering portion F1 ; a subtract means M2 which calculates a differential signal of the audio signals input to the first and second terminals 1 and 2 and inputs the differential signal to the second filtering portion F2 ; an adding means M10 which adds output signals of the first and the second filtering portions F1 and F2 so as to produce a first L-processed signal or a second L-processed signal; a subtract means M11 which subtracts output signal of the second filtering portion F2 from that of the first filtering portion F1 so as to produce a first R-processed signal or a second R-processed signal. Typically, the shuffler type filter is used in the case where the left and the right speakers SPL and SPR and the left and the right sound image (virtual speakers) ZL and ZR are symmetrically arranged with respect to the listener M. In the above-mentioned case, transfer functions H SUM and H DIF of the first and the second filtering portions F1 and F2 will be described. The transfer functions H SUM and H DIF can be obtained by using the above-mentioned head-related transfer functions h LL , h LR , h RL , h RR , h L'L , h L'R , h R'L and h R'R as follows: Initially, since the speakers (the actual and the virtual speakers) are symmetrically arranged with respect to the listener, the relationship of h LL =h RR , h LR =h RL , h L'L =h R'R and h L'R =h R'L are satisfied in equations (6) to (9). As a result, H 11 =H 22 and H 12 =H 21 are satisfied. Next, if using h a for h LL and h RR , h b for h LR and h RL , h a' for h L'L and h R'R , and h b' for h L'R and h R'L , then the transfer functions H SUM and H DIF are represented by the following equations: H SUM = (h a' +h b' ) / (h a +h b ) H DIF = (h a' -h b' ) / (h a -h b ) In Figure 1 , K1L and K1R respectively denotes a first L-coefficient multiplying means and a first R-coefficient multiplying means. The first L- and R-coefficient multiplying means K1L and K1R respectively multiplies the first L-processed signal and the first R-processed signal (which signals are from the first signal-processing means 11 ) by a coefficient k. The coefficient k arbitrarily varies in the range of 0 to 1. K2L and K2R respectively denotes a second L-coefficient multiplying means and a second R-coefficient multiplying means. The second L- and R-coefficient multiplying means K2L and K2R respectively multiplies the second L-processed signal and the second R-processed signal (which signals are from the second signal-processing means 12 ) by a coefficient 1-k. Preferably, a spectrum of the coefficient k has 1/f characteristics. Since the 1/f characteristics provides a physiological nature, an unnatural feeling of a listener can be eliminated by using the coefficient having 1/f characteristics. A method for producing the coefficient having 1/f characteristics will be described below. As shown in Figures 5, 6A and 6B , the method includes outputting as a random signal an M-sequence signal from a random signal generator (e.g., a digital signal processor) PR. The signal is formed to be a pulse having rectangular shape, height of 1, and random width and pitch. The M-sequence signal is multiplied by a coefficient a o in a scaling portion SC1 so as to reduce a possibility that an output value in the succeeding step exceeds 1, and then, as shown in Figure 6B , integrated with respect to time in an integration circuit SK . The integration circuit SK includes: a delay circuit J which delays an input signal by one sampling period; a coefficient multiplying means K4 which multiplies an output of the circuit J by a coefficient b 1 ; an adding means (e.g., mixer) M4 which adds an output of the coefficient multiplying means K4 to the input signal to the integration circuit SK . The output signal from the integration circuit SK is supplied to an overflow limiter L having a maximum limit value of 1, so as to produce a coefficient k. In the above-mentioned method, the scaling portion SC1 and the overflow limiter L can be omitted. An alternative method will be described with reference to Figures 7 and 8A to 8C . It is believed that, in many cases, a spectrum of a music signal essentially has 1/f characteristics. Therefore, in such a case, the method includes supplying an audio signal (2-channel stereophonic signal in Figure 7) to a signal-selecting circuit (e.g., an adding and subtracting circuit) SE and selecting a signal for producing a coefficient from a signal of one of the channels, an added signal of the both channel, or a differential signal of the both channel. Then, the selected signal (shown in Figure 8A ) is squared by a squaring circuit SQ as shown in Figure 8B. The squared signal is multiplied by an appropriate coefficient in a scaling portion SC2 so as to reduce a possibility that an output value in the succeeding step exceeds 1. Then, an output signal from the scaling portion SC2 is processed through a low pass filter LPF having a cut-off frequency of about 10 Hz so as to produce a coefficient k (Figure 8C ). In Figure 1 , M6 and M7 respectively denotes an adding means (e.g., a mixer). The adding means M6 adds the first L-processed signal and the second L-processed signal both of which have been multiplied by the coefficient, and supplies the added signal to the left speaker SPL. The adding means M7 adds the first R-processed signal and the second R-processed signal both of which have been multiplied by the coefficient, and supplies the added signal to the right speaker SPR. For example, in the case of making the listener M recognise the sound image at the predetermined position P located at an angle  (e.g., 120 degrees) counter-clockwise away from the front F of the listener M, this embodiment of the present invention includes producing, by the first signal-processing means 11, the first L-processed signal and the first R-processed signal for localising the sound image at the first localization position P1 which is in the vicinity of the predetermined position P and located at an angle  1 (e.g., 90 degrees) counter-clockwise away from the front F of the listener; and producing, by the second signal-processing means 12, the second L-processed signal and the second R-processed signal for localizing the sound image at the second localization position P2 which is in the vicinity of the predetermined position P and located at an angle  2 (e.g., 150 degrees) counter-clockwise away from the front F of the listener. Next, the first L-processed signal and the first R-processed signal are multiplied by a coefficient k (which randomly varies in the range of 0 to 1), and simultaneously the second L-processed signal and the second R-processed signal are multiplied by a coefficient 1-k. Then, the multiplied first L-processed signal and the multiplied second L-processed signal are added by the adding means M6 so as to be supplied to the left speaker SPL, and simultaneously the multiplied first R-processed signal and the multiplied second R-processed signal are added by the adding means M7 so as to be supplied to the right speaker SPR. Accordingly, the first and the second L-processed signals added in a random ratio are supplied to the left speaker SPL, the first and the second R-processed signals added in a random ratio are supplied to the right speaker SPR . The speakers SPL and SPR output a sound wave. As a result, sound image is localized at a first and a second localization positions P1 and P2. Furthermore, a sound volume from the first and the second localization positions P1 and P2 is randomly varied. According to the above-mentioned embodiment, even when the sound image is static at the position sideward and rearward of a listener M , it is possible to make the listener M clearly recognize that the sound image is at the predetermined position P. Furthermore, since the sound volume from the first localization position P1 randomly varies, there is no concern to provide the listener M with an unnatural feeling. Especially, when the coefficient k has 1/f characteristics, the sound volume variation from the first and the second localisation positions P1 and P2 is physiologically natural, thereby providing the listener M with a further natural feeling. As described above, according to the present embodiment, an apparatus and a method for localising sound image, which make a listener clearly recognise that the sound image is at the predetermined position and provide a listener with a natural feeling, can be obtained. Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be construed broadly.

Claims: A method of localising a sound image, comprising the steps of: providing a left speaker (SPL) and a right speaker (SPR) in front of a listener; subjecting an audio signal to a sound image localisation treatment by producing a first processed signal which localises the sound image at a first localisation position (P1) and a second processed signal which localises the sound image at a second localisation position (P2); multiplying one of the first and the second processed signals by a coefficient k which varies in a range of 0 to 1; multiplying the other one of the first and the second processed signals by a coefficient 1-k; and adding the processed signal multiplied by the coefficient k and the processed signal multiplied by the coefficient 1-k; and supplying the processed signal to the left and the right speakers (SPL, SPR), so as to localise the sound image at a predetermined position (P); wherein, when the predetermined position is located at an angle  in a circumferential direction away from the front (F) of the listener (M), the first localisation position (P1) is in the vicinity of the predetermined position (P) and located at an angle  1 in the circumferential direction away from the front (F) of the listener (M) wherein  1 < , and the second localisation position (P2) is in the vicinity of the predetermined position (P) and located at an angle  2 in the circumferential direction away from the front (F) of the listener (M) wherein  2 > ; which method is characterised in that : the step of multiplying by the coefficient k is performed using as the coefficient a coefficient which varies in the range of 0 to 1 at random. A method according to claim 1, wherein the spectrum of the coefficient k has 1/f characteristics. A method according to claim 1, which includes producing the coefficient k by generating a random signal having rectangular pulse shape, uniform, height and random pulse width and pitch, and integrating the random signal in an integration circuit (SK: J, K4, M4). A method according to claim 1, which includes producing coefficient k by squaring the audio signal by a squaring circuit (SQ), and passing the squared signal through a low pass filter (LPF). A method according to claim 4, which includes a step of producing the coefficient k using a signal wherein the audio signal is a 2-channel stereophonic signal, and the signal for producing the coefficient k is selected from one or other of the channel signals, the sum of both of the channel signals, or the difference of both of the channel signals. An apparatus for localising a sound image, comprising: left and right speakers (SPL, SPR) to be provided in front of a listener (M); a means (11,12) for subjecting an audio signal to a sound image localisation treatment comprised of a means (11) for producing a first processed signal which localises the sound image at a first localisation position (P1), and a means (12) for producing a second processed signal which localises sound image at a second localisation position (P2); a means for producing a coefficient k which varies in the range of 0 to 1; a means (K1L, K1R) for multiplying one of the first and the second processed signals by the coefficient k; a means (K2L, K2R) for multiplying the other signal by a coefficient 1-k; and a means (M6,M7) for adding the processed signal multiplied by the coefficient k and the processed signal multiplied by the coefficient 1-k and supplying the added signal to the left and the right speakers (SPL,SPR) so as to localise the sound image at a predetermined position (P); wherein, when the predetermined position (P) is located at an angle  in a circumferential direction away from the front (F) of the listener (M) , the first localisation position (P1) is in the vicinity of the predetermined position and located at an angle  1 in the circumferential direction away from the front (F) of the listener wherein  1 < , and the second vocalisation position (P2) is in the vicinity of the predetermined position (P) and located at an angle  2 in the circumferential direction from the front (F) of the listener (M) wherein  2 > ; which apparatus is characterised in that : the means for producing the coefficient k is a means (PR, SC1, SK, L; SE, SQ, SC2, LPF) that produces, as the coefficient k, a coefficient which varies in the range of 0 to 1 at random. An audio signal processor, comprising: processor means (11, 12, KIL-K2R, M6, M7)) for subjecting an audio signal to a sound image localisation treatment so as to produce a processed signal; and supply means (3,4) for supplying the processed signal to left and right speakers (SPL), SPR) to produce a localised sound image at a predetermined position P); wherein the processor means comprises: means (11) for producing a first processed signal which is to produce a localised sound image at a first localisation position (P1); means (12) for producing a second processed signal which is to produce a localised sound image at a second localisation position (P2); means (K1L, K1R) for multiplying one of the first and the second processed signals by a coefficient k; means (K2L, K2R) for multiplying the other signal by a coefficient 1-k; and means (M6,M7) for adding the processed signal multiplied by the coefficient k and the processed signal multiplied by the coefficient 1-k and outputting the added signal, as said processed signal, to said supply means (3,4); wherein, when the predetermined position (P) is located at an angle  in a circumferential direction away from the front (F) of a listener (M), the first localisation position (P1) is in the vicinity of the predetermined position (P) and located at an angle  1 in a circumferential direction away from the front (f) of the listener (M) wherein  1 <, and the second localisation position (P2) is in the vicinity of the predetermined position (P) and located at an angle  2 in a circumferential direction away from the front (F) of the listener (M) wherein  2 > ; which audio signal processor is characterised by a means (PR, SC1, SK, L; SE, SQ, SC2, LPF) for producing the coefficient k as a coefficient which varies in the range of 0 to 1 at random.

Inventors: KASAI JOJI, NAKATAKE TETSURO, SADAIE KOICHI, TAKEMURA KAZUMASA, TOYOFUKU KENICHIRO, KASAI, JOJI, NAKATAKE, TETSURO, SADAIE, KOICHI, TAKEMURA, KAZUMASA, TOYOFUKU, KENICHIRO
Applicants: ONKYO KK, ONKYO CORPORATION
Application year: 1999
Main classification: H04S1
IPC codes: H04S1