Pitch invariant frequency lowering with nonuniform spectral compression

A technique for improving speech reception for persons with high frequency hearing loss based on pitch invariant frequencg lowering of the short term spectral envelope is described. The speech signal is segmented pitch synchronously, processed by a technique described by oppenheim and Johnson (1) to achieve nonuniform spectral warping, dilated in time to achieve frequencg lowering, and resynthesized with the original periodicity. Both the overall bandwidth reduction and the relative compression of low and high frequency components can be specified. Spectrographic examples illustrating the range of transformations achieved are presented to illustrate the capability of the system.