Adaptive Audio Limited

Ole Kirkeby

Philip Arthur Nelson

Hareo Hamada

Felipe Orduna-Bustamante

Sound recordings are played through a closely-spaced pair of loudspeakers with a predetermined listener position having an included angle of between 6&#xb0; and 20&#xb0;, and filter means being employed in creating said sound recordings, the filter means having characteristics such that when the sound recordings are played, the need to provide a virtual imaging filter means at the inputs to the loudspeakers to create virtual sound sources is avoided, the sound recording being such that when played through the loudspeakers a phase difference between vibrations of the two loudspeakers results where the phase difference varies with frequency from low frequencies where the vibrations are substantially out of phase to high frequencies where the vibrations are in phase, the lowest frequency at which the vibrations are in phase being determined approximately by a ringing frequency, f.

Sound recording and reproduction systems

A method of recording sound for reproduction by a plurality of loudspeakers, or for processing sound for reproduction by a plurality of loudspeakers, is described in which some of the reproduced sound appears to a listener to emmanate from a virtual source which is spaced from the loudspeakers. A filter means (H) is used either in creating the recording, or in processing the recorded signals for supply to loudspeakers, the filter means (H) being created in a filter design step in which: a) a technique is employed to minimise error between the signals (w) reproduced at the intended position of a listener on playing the recording through the loudspeakers, and desired signals (d) at the intended position, wherein: b) said desired signals (d) to be produced at the listener are defined by signals (or an estimate of the signals) that would be produced at the ears of (or in the region of) the listener in said intended position by a source at the desired position of the virtual source. A least squares technique may be employed to minimise the time averaged error between signal reproduced at the intended position of a listener and the desired signal, or it may be applied to the frequency domain.

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Tokyo, Japan

Ole Kirkeby