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.