Abstract: A compressing system for digital modulated signals comprises an analog-to-digital converter for obtaining a digital modulated signal by digitally modulating an analog signal; a first variable gain circuit provided at the output side of the analog-to-digital converter; and a first gain control circuit for equivalently performing level-compression of the analog conversion level of the input digital modulated signal of the first gain control circuit within a predetermined level range by use of a first control signal and the first variable gain circuit. The first gain control circuit comprises an expected signal generating circuit having an analog conversion level z.sub.n which satisfies the equation ##EQU1## (N is an arbitrary natural number, and a.sub.O through a.sub.N are zero or an arbitrary number) where y.sub.

Abstract: A binaural sound reproducing system includes a transducer for translating the recorded binaural information into an electrical signal on each of separate channels and a convolution integrator on each separate channel connected to receive the output from the transducer to compensate for acoustical differences resulting from the facial difference between the dummy head used for recording the binaural signal and a particular listener.

Abstract: A binaural four-channel stereophony comprises at least two dummy heads each provided with microphones at the ears of the dummy to pick up signals from various sound sources or groups of sound sources. The binaural signals representing each sound source or a group of sound sources are coupled to an acoustic crosstalk cancellation circuit and eventually applied to two front or two rear loudspeakers. Each sound source or group of sound sources is localized between adjacent ones of the four speakers to simulate the binaural effect produced in a closed-circuit type binaural sound reproducing system.