Electrical audio signal processing systems and devices – Binaural and stereophonic – Pseudo stereophonic
Patent
1995-09-08
1998-08-18
Isen, Forester W.
Electrical audio signal processing systems and devices
Binaural and stereophonic
Pseudo stereophonic
381 25, H04S 500, H04R 502
Patent
active
057968438
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a video signal and audio signal reproducing apparatus for reproducing an audio signal through headphones while a listener is watching a picture, for example.
BACKGROUND ART
There has conventionally been a method of reproducing an audio signal with using headphones which a listener puts on the head with his both ears covered therewith to listen to the audio signal from the both ears. When the method of reproducing the audio signal through the headphones is employed, there occurs a phenomenon referred to as a so-called lateralization in which a reproduced sound image is perceived inside a head of the listener even if the audio signal from a signal source is a stereophonic signal.
On the other hand, the system of reproducing the audio signal through the headphones includes a binaural sound-wave pickup and reproduction system. The binaural sound-wave pickup and reproduction system is the following system. Microphones, so-called dummy-head microphones, are located in left and right auricles of a dummy head which is made to imitate the listener's head. An audio signal from a signal source is picked up by the dummy-head microphones. When the audio signal thus picked up is reproduced and the listener actually listens to the reproduced audio signal with the headphones, the listener can obtain presence with which the listener feels as if he listened to the sounds directly from the signal source. According to the binaural sound-wave pickup and reproduction system, it is possible to improve the picked-up and reproduced sound image in directivity, localization, presence and so on. However, when the above-mentioned binaural reproduction is carried out, it is necessary to provide a signal source as a special source which is picked up by the dummy-head microphones as a sound source signal and different from that use for reproduction with speakers.
It has been supposed to achieve, by applying the above-mentioned binaural sound-wave pickup and reproduction system, a reproduction effect in which a general stereophonic signal is reproduced through the headphones and a reproduced sound image is localized outside the head (at a speaker position) similarly to the reproduction by the speakers. With this arrangement, when the headphones are used for reproduction, the same effect as the reproduction with the speakers is achieved and an effect in which the reproduced sound is prevented from being leaked to the outside is further achieved due to the headphones. However, when stereophonic reproduction is carried out by using the speakers, even if the listener changes the direction of his head (face), absolute direction and position of a sound image are not changed and only relative direction and position of the sound image the listener perceives are changed. On the other hand, in the case of the binaural reproduction using the headphones, even if the listener changes his head (face), the relative direction and position of the sound image which the listener perceives are not changed. Therefore, even if the binaural reproduction is carried out by using the headphones, then when the listener changes the direction of the head (face), the sound image is formed inside the listener's head. It is particularly difficult to effect a so-called forward localization, i.e., to localize the sound image in front of the listener. Moreover, in this case, the sound image tends to be elevated above the head and hence becomes unnatural.
According to a reproduction method using headphones disclosed in Japanese patent publication No. 42-227, on the contrary the following binaural reproduction system using headphones is supposed. Specifically, directivity and localization of a sound image are determined by difference in volume, time, phase and so on between sounds perceived by left and right ears of the listener. The system disclosed in the above publication has a level control circuit and a variable delay circuit in an audio signal line of each of left and right channels and also has a means for detecting
REFERENCES:
patent: 4817149 (1989-03-01), Myers
patent: 5181248 (1993-01-01), Inanaga et al.
patent: 5495534 (1996-02-01), Inanaga et al.
patent: 5495576 (1996-02-01), Ritchey
patent: 5526183 (1996-06-01), Chen
Inanaga Kiyofumi
Yamada Yuji
Isen Forester W.
Maioli Jay H.
Sony Corporation
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