Abstract: An apparatus for realistically reproducing sound, particularly for sound based on a stereophonic signal having dialog and effects and associated with an accompanying video image. The apparatus includes a front speaker located in proximity to the video image for providing acoustic output based upon a summation signal of the component left and right (L+R) channels of the audio signal. A rear speaker located to the rear of the viewing area provides acoustic output based upon a difference signal, (L-R) or (R-L), between the left and right channels. Left and right speakers located to the respective left and right sides of the viewing area output audio based upon the respective left or right channels. The left and right channels speakers reproduce in one embodiment the respective left and right channels of the audio signal and in a second embodiment reproduce a difference signal, (L-R) or (R-L).

Abstract: An audio noise gate having a main audio circuit having a filter with a control terminal for determining frequency response and having at least two different roll-off frequencies including one that rolls-off high end content audio signals and one that passes high end content audio signals. The main circuit is controlled from two secondary circuits one including a high pass filter for determining high frequency content of the audio signal and the other comprising a signal detection circuit including a peak detector for determining absence or presence of a note. The signal detection circuit operates in combination with the high pass filter circuit to provide for automatic adjustment of the noise gate to control the release time, quickly for short notes and slowly for held notes. The output of the high pass filter circuit also includes a peak detector and a gain stage for controlling the frequency response of the main circuit.