Electrical audio signal processing systems and devices – Binaural and stereophonic – Pseudo stereophonic
Patent
1996-06-21
1998-05-12
Harvey, Minsun Oh
Electrical audio signal processing systems and devices
Binaural and stereophonic
Pseudo stereophonic
381 24, H04R 500
Patent
active
057518157
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to apparatus for adjusting audio signals for improving a stereophonic effect of reproduced sound.
It is known that to achieve balance control in a listening environment is desirable for listening to binaural or stereophonic recordings For example, a listener situated between two loudspeakers of a stereophonic hi-fi system and who is not positioned midway between the loudspeakers will, if these loudspeakers are operating at the same power output levels, receive imbalanced sound intensity levels at the left and right ears from the two loudspeakers. Thus by attenuating the power output of the loudspeaker nearer the listener, a balance between the received sound intensity levels may be achieved.
However, control of sound intensity levels on their own may not lead to a totally satisfactorily balanced sound-field. It is known to delay relatively the outputs of the loudspeakers so that each loudspeaker is apparently the same distance away from the listener regardless of their actual positions. This can be achieved by phase- or time-delay of the signals supplied to the loudspeakers. EP-A-0,357,034 discloses such a system. In this system an amplitude attenuator and a phase delay are serially connected in each of two stereophonic channels between a music source and a left and right loudspeaker. A balance control is manually adjusted so that attenuation and delay are concomitantly altered in each of the channels. This alteration is achieved by modifying the signals within each channel with values stored in memories. Thus the concomitant alteration permits apparent relative movement of the loudspeakers as well as control of the relative sound intensity level outputs of the loudspeakers.
GB-A-1598746 relates to a system in which a monophonic signal is converted to binaural signals providing positional information in the X-Y plane of the loudspeakers by means of a circuit located in the sound reproducing apparatus. The circuit includes variable attenuators, filters and delay elements which are under user control to create a desired sound-position effect.
Whilst the systems described in EP-A-0,357,034 and GB-A-1598746 function adequately to achieve balance in a sound-field between the two loudspeakers, this balance--and thus the sound field--is only adjustable in a plane in which the loudspeakers are situated.
However, there are situations where a stereophonic or binaural effect is diminished or degraded because of the relative position of the direction in a vertical azimuthal plane in which the listener is facing and an imaginary plane containing the loudspeakers and the listener's head. For example, if a listener is reclining on an armchair with his head inclined at an angle to the horizontal, then the ears will detect the sound is coming from a direction downward of the listener's head, and this may degrade the stereophonic effect.
The present invention relates generally to any type of reproduced sound having the quality of three dimensions, whether the sound is reproduced from monophonic, stereophonic or binaural signals; for the purposes of this specification such reproduced sound will be referred to as stereophonic.
It is an object of the present invention to provide a means of adjustment of stereophonic sound such that it is possible to compensate for the orientation of the listener's head relative to the sound transducers in a vertical azimuthal plane. Accordingly, the present invention provides audio signal adjustment apparatus including left and right signal channels for connection to respective left and right sound transducers, means within each channel for adjusting signal parameters for varying the stereophonic effect produced by the transducers, such adjusting means including azimuthal adjustment means for adjusting the stereophonic effect in dependence on the azimuthal orientation of the direction a listener's head is facing in relation to an imaginary plane containing the listener's head and the sound transducers, the azimuthal adjustment means including a filter means with a
REFERENCES:
patent: 5181248 (1993-01-01), Inaniga
patent: 5371799 (1994-12-01), Lowe
Jack Hebrank and D. Wright, "Spectral cues used in the localization of sound sources on the median plane", J. Acoust. Soc. Am., Vo. 56, No. 6, Dec. 1974, pp. 1829-1834.
Clemow Richard David
Nackvi Fawad
Philp Adam Rupert
Sibbald Alastair
Central Research Laboratories Limited
Harvey Minsun Oh
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