Patent ID: 6993480
Filing Date: 2006-01-31
Classification: G10L,H04R

Abstract:
1. A system for enhancing intelligibility of a voice signal that is degraded by factors that reduce intelligibility of the voice signal, said system comprising: an input configured to receive a voice signal that includes human spoken words; an aural filter operatively coupled to said input, said aural filter configured to filter said voice signal to produce a filter output signal wherein low frequencies below speech frequencies and high frequencies above speech frequencies are attenuated with respect to speech frequencies; a speech expander operatively coupled to said aural filter to produce an expanded signal, said speech expander configured to amplify said filter output signal according to an amplifier gain, wherein said amplifier gain is a function of an envelope amplitude of said filter output signal; and a combiner configured to combine at least a portion of said expanded signal and at least a portion of said voice signal to produce an enhanced signal representing said spoken words; wherein, when the voice signal is operating a high volume levels, the system emphasizes middle speech frequencies over low and high frequencies; and wherein, when the voice signal is operating at low volume levels, the system provides more low and high frequency components of the voice signal than when the voice signal is operating a high volume levels; such that the system provides a transfer function which approximates an inverse of the transfer function of human hearing.