Electrical audio signal processing systems and devices – Binaural and stereophonic – Hearing aid
Patent
1995-05-23
1997-11-11
Kuntz, Curtis
Electrical audio signal processing systems and devices
Binaural and stereophonic
Hearing aid
381 74, H04R 500
Patent
active
056872399
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an audio reproduction apparatus suitable for use in reproducing audio signals through headphones.
BACKGROUND ART
There has conventionally been known a process of reproducing audio signals through headphones which are placed on the head of a listener in covering relation to the ears of the listener to allow the listener to listen to the audio signals with the headphones. The process of reproducing audio signals through headphones creates a phenomenon referred to as "lateralization" in which a reproduced sound image is perceived inside the head of the listener even when the signal from a signal source is of a stereophonic nature.
Another process of reproducing audio signals through headphones is known as a binaural process of picking up and reproducing sound waves. The binaural process of picking up and reproducing sound waves will be described in detail below. Microphones called "dummy head microphones" are put into the respective ears of a dummy head which simulates the head of a listener, and an audio signal from a signal source is picked up by the dummy head microphones. The audio signal thus picked up are reproduced by headphones that are actually worn by a listener, who is capable of listening to the reproduced sound with presence or intimacy. The binaural process allows the listener to listen to the reproduced sound image with improved directivity, localization, and presence. However, binaural sound reproduction requires a special sound source signal picked up by dummy head microphones which is different from a sound source signal used for sound reproduction by loudspeakers.
It has been proposed, in an application of the binaural process of picking up and reproducing sound waves, to reproduce a general stereophonic signal with headphones in order to bring about a phenomenon called "localization" in which a reproduced sound image is perceived outside the head of the listener, in the same manner as sounds reproduced by loudspeakers. In a stereophonic sound reproduction mode using loudspeakers, when the listener changes the direction of his head (face), the absolute direction and position of the sound image remain unchanged, but the relative direction and position of the sound image as it is perceived by the listener change. In a binaural sound reproduction mode using headphones, the relative direction and position of the sound image remain unchanged when the orientation of the head (face) of the listener is changed. In the binaural sound reproduction mode, therefore, when the listener changes the orientation of the head (face), the sound field is perceived by the listener as being located inside the head, and it is difficult to localize the sound image in front of the listener. When the listener changes the orientation of the head (face) in the binaural sound reproduction mode, the perceived sound image tends to be elevated inside the head.
Japanese patent publication No. 42-227 discloses a binaural sound reproduction system using headphones as follows: The directivity and localization of a sound image as perceived by a listener are determined by the difference between the intensities of sounds perceived by the respective ears of the listener, the difference between the times of arrival of the sounds at the respective ears of the listener, and the phase difference between the sounds. The disclosed system has a level control circuit and a variable delay circuit in the audio signal line of each of the left and right channels. The level control circuit and the variable delay circuit for controlling audio signals in each of the left and right channels are controlled based on a signal indicative of the detected orientation of the head of the listener.
In the binaural sound reproduction system disclosed in Japanese patent publication No. 42-227, the signal indicative of the detected orientation of the head of the listener is used to directly energize motors to mechanically control a variable resistor and a variable capacitor in the level control circuit and
REFERENCES:
patent: 3962543 (1976-06-01), Blanert et al.
patent: 5181248 (1993-01-01), Inanaga et al.
patent: 5452359 (1995-09-01), Inanaga et al.
patent: 5495534 (1996-02-01), Inanaga et al.
patent: 5526429 (1996-06-01), Inanaga et al.
Inanaga Kiyofumi
Yamada Yuji
Kuntz Curtis
Maioli Jay H.
Mei Xu
Sony Corporation
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