Stereophonic signal processor

An audio signal processor (10) responsive to an input sound source signal S (21) and arranged to produce a pseudo stereo effect in a plurality of output signals (22) directionally encoded for reproduction via a predetermined directional encoding system, the audio signal processor including filtering means (1a,1b,2L,2R,11L,11R) arranged to vary the encoded direction across a directional sound stage of an output signal as the frequency of the input sound source signal varies:

• characterised in that the filtering means (1a,1b,2L, 2R,11L,11R) have a gain magnitude characteristic relative to the encoding law of the encoding system which is substantially independent of frequency and an amplitude/phase characteristic as a function of frequency which follows the encoding law of the encoding system for substantially all audio frequencies within the operational bandwidth of the system and encodes the output signal according to the encoding law for reproduction from a direction P' across a directional sound stage P", the direction P' varying with the frequency of the source signal S.

A method of processing an audio signal S (21) to produce a pseudo stereo effect in a plurality of output signals (22) directionally encoded for reproduction via a predetermined directional encoding system, comprising filtering the input sound source signal S (21) thereby varying the encoded direction across a directional sound stage of a corresponding output signal as the frequency of the input sound source signal S (21) varies, the reproduced energy gain of the output signal being substantially constant with frequency:

• characterised in that the phasiness Q introduced by the step of filtering is substantially zero for at least three positions in space within the directional sound stage.

A method of processing an audio sound source signal S (21) to produce a pseudo stereo effect in a plurality of output signals (22) directionally encoded for reproduction via a predetermined directional encoding system, including the step of filtering the input audio signal S (21) thereby varying the encoded direction across a directional sound stage of an output signal as the frequency of the input sound source signal (21) varies:

• characterised in that the output signals are directionally encoded with a gain magnitude substantially independent of frequency and with an amplitude/phase characteristic which follows the encoding law of the encoding system for substantially all audio frequencies within the operational bandwidth of the system thereby encoding the output signal according to the encoding law for reproduction from a direction P' across a directional sound stage P", the direction P' varying with the frequency of the source signal S.