Patent ID: 8085959

Claim:
An audio output device, comprising: an acoustic input transducer for converting input acoustical energy into output electrical signals corresponding to the input acoustical energy; a plurality of audio bandpass filters coupled to receive said electrical signals, each of said audio bandpass filters having an output; and a plurality of multiplicative automatic gain control (MAGC) circuits coupled to a respective output of one of said plurality of audio bandpass filters, at least one of said MAGC circuits including a hearing compensation circuit and a noise suppression circuit, and wherein at least one of said MAGC circuits include: a first circuit to obtain an input envelope amplitude from the coupled audio bandpass filter output; a second circuit responsive to the input envelope amplitude to provide a logarithm of the input envelope amplitude; a noise estimation circuit for obtaining an estimate of noise; and a subtraction circuit to subtract the estimate of noise from the logarithm of the input envelope amplitude; wherein an acoustic signal having approximately a constant amplitude for a period of a predetermined amount of time is attenuated through interaction of said hearing compensation circuit and said noise suppression circuit.