1. A method for frequency-lowering of audio signals for improved speech perception, comprising: receiving, by an analysis module of a device, a first audio signal; detecting, by the analysis module, one or more spectral characteristics of the first audio signal, the detected one or more spectral characteristics corresponding to one or more respective non-sonorant sounds; classifying, by the analysis module, the one or more respective non-sonorant sounds, based on the detected one or more spectral characteristics of the first audio signal; selecting, by a synthesis module of the device, a second audio signal from a plurality of audio signals, responsive to at least the classification of the one or more respective non-sonorant sounds; and combining, by the synthesis module of the device, at least a portion of the first audio signal with the second audio signal for output to form a combined audio signal with frequency characteristics audible to the user.
9. The method of claim 1 wherein selecting the second audio signal further comprises: selecting the second audio signal from the plurality of audio signals responsive to the classification of the one or more non-sonorant sounds in the first audio signal, each of the plurality of audio signals comprising a plurality of noise signals and each having a different spectral shape, and wherein the spectral shape of each of the plurality of audio signals is based on the relative amplitudes of each of the plurality of noise signals at a plurality of predetermined frequencies.