Multiband programmable compression system

A signal compressor having a programmable compression ratio, comprising:

• a variolosser having an input terminal for receiving an audio frequency electrical signal having a waveform, an output terminal, and first and second control means, the gain of said variolosser between said input and said output being controlled by the ratio of the currents through said first and second control means;
• detector means for providing a control signal current responsive to the amplitude of said input signal;
• means for applying said control signal current to said first control means;
• programming means for providing a programming current to said second control means;
• signal feedforward means having an input end and an output end, the input end of said feedforward means being connected to a source of an electrical signal having the same waveform received at said input terminal and the output end of said feedforward means being connected to said output terminal of said variolosser, for providing a signal at said output terminal proportional to said input electrical signal.

A multiband audio frequency signal compressor, comprising:

• a band split filter for dividing an electrical signal, representative of an acoustical signal, into a plurality of band-limited electrical signals having separate frequency ranges;
• a plurality of limiter means each having an input terminal connected to an output of said band split filter, and an output terminal;
• each of said limiter means having a separately programmable maximum output level;
• and,
• a plurality of feedforward means, each feedforward means having an input end and an output end, the input end of each feedforward means being connected to an output of said band split filter, such that the signal applied to each feedforward means is in the same frequency range as the signal applied to a limiter means, and the output end of each feedforward means being connected to a limiter output terminal, for providing a signal at said output terminal which is proportional to said band limited electrical signal.

A hearing aid, comprising:

• an input transducer for converting ambient sounds into an electrical signal representative of the sounds;
• band split filter means for dividing said electrical signal into a plurality of band-limited electrical signals of predetermined frequency range;
• a plurality of individually programmable compressors for providing compressed output signals based on said band-limited electrical signals;
• control means for controlling the frequency ranges of the outputs of said band split filter means, the compression ratio of each of said compressors, and the gain of each of said compressors;
• means for combining the outputs of said compressors;
• an output transducer for converting the combined output of said compressors into an acoustical signal;
• wherein each said compressor comprises a variable gain limiter means having as its input one of said band-limited electrical signals, said limiter means producing an output signal with a gain set by said control means, a circuit in parallel to said limiter means for providing a signal at the output of said limiter means which is proportional to said band-limited electrical signal, and a variable gain amplifier whose input is the combined output from said limiter means and said parallel circuit.