Circuit arrangements for modifying dynamic range using variable combining techniques

摘要

The circuit arrangements for modifying the dynamic range of signals, particularly compressors and expanders for use in noise reduction compander systems, have the advantages of fixed band characteristics (variable attenuation throughout all or part of the frequency band) and sliding band characteristics (variable attenuation through part of the frequency band achieved by a variable pass filter), without the disadvantages normally inherent in each characteristic. The outputs of fixed band and sliding band circuits (74 and 72) variably selected by a combining means (60) operated by a control circuit (70) which senses signal frequencies and/or levels, the circuits (74 and 72) operating in generally the same level range and at least a partial overlapping in frequency range, optionally also in parallel with a filter circuit (76) with fixed characteristics.