1. A method for transforming an audio signal comprising: obtaining a primary channel of an audio signal with a primary microphone of an audio device; obtaining a reference channel of the audio signal with a reference microphone of the audio device; estimating spectral magnitudes of each of the primary channel and reference channel of the audio signal for a plurality of frequency bins; transforming one or more of the spectral magnitudes of the primary channel and of the reference channel by applying at least one of a fractional linear transformation and a higher order rational functional transformation to produce one or more transformed spectral magnitudes of the primary channel and of the reference channel; emphasizing the primary channel when the transformed spectral magnitude of the primary channel is stronger than the transformed spectral magnitude of the reference channel; deemphasizing the primary channel when the transformed spectral magnitude of the reference channel is stronger than the transformed spectral magnitude of the primary channel; wherein the emphasizing and deemphasizing include computing a multiplicative resealing factor and applying the multiplicative rescaling factor to a gain computed in a prior stage of a speech enhancement filter chain when there is a prior stage, and directly applying a gain when there is no prior stage; and wherein the emphasizing and deemphasizing adjust a degree of filtering to isolate the voice data in the audio signal and to thereby enhance output of the voice data.