Stereo image separation and perimeter enhancement

Abstract

Abstract A stereo enhancement system utilizes a difference signal derived from the left and right stereo channels in which the difference signal is delayed, amplified, and then added into the appropriate channels to cancel left/right speaker mixing at the listener's ears, thereby to improve stereo separation without center region distortion. Depending on the amplification level of the difference signal, an increase in the perimeter sound over that produced at the central region gives a "wrap around" effect with only two speakers by increasing the volume of only the left/right directional sound components relative to centrally located sounds which have no left/right directionality. In order to compensate for the angle between the listener and the speakers, a continuously variable delay is provided in the 100 microsecond -1 millisecond range by the utilization of a serial analog delay bucket brigade device. Ultrashort delays are created, in one embodiment, by utilizing equal delays in the left and right stereo channels. The difference signal is then delayed by an amount equal to either of the two initial delays plus the amount of desired delay. When serial analog delay devices are utilized, the clock rate of the delay line used for the difference signal is made slightly lower than the clock rate of the delay lines utilized in initially delaying the left/right signals, thereby to provide for ultrashort delayed difference signals. Off-center listener positions are accommodated by a further continuously variable delay line in one or the other of the left and right channels. In alternative embodiments to minimize the noise characteristic of analog delay devices, the input signal to the device is compressed, followed by expansion of the output signal from the device.

Inventors

• 👤 Joel M. Cohen

Bibliographic Details