Abstract: A sound transmission and reproduction system including at the transmitter side means for producing a non-audible control signal indicative of a predetermined character of the transmitted sound, preferably the intensity of the sound as actually transmitted, whereby the transmitted sound may be artificially attenuated and amplified, respectively, in respective passages of high and low intensity so as to be transmittable within a restricted dynamic range. At the receiver side the control signal is detected and used for controlling the amplifier as an automatic volume control so as to effect extra amplification of the attentuated passages and attenuation of the artificially amplified passages so as to enable the reproduction to take place with the full dynamic range of the original sound.

Abstract: A sound reproduction system of the MFB-type (motional feedback), comprising an amplifier and a loud speaker system, the woofer of which is provided with a transducer producing in the lower frequency range a feedback signal proportional to the accelerations of the woofer membrane. The loudspeaker system is provided with a filter connected to the main signal input and designed so as to produce a reference signal in accordance with the expected ideal transfer function of the woofer and its associated crossover filter.