13. A system for adjusting a voice intelligibility enhancement, the system comprising: a linear predictive coding analysis module configured to apply a linear predictive coding (LPC) technique to obtain LPC coefficients that correspond to a spectrum of an input voice signal, the spectrum comprising one or more formant frequencies; a mapping module configured to map the LPC coefficients to line spectral pairs; a formant enhancement module configured to modify the line spectral pairs with one or more processors by at least applying a modulation factor to the line spectral pairs to decrease a distance between the line spectral pairs and thereby produce an enhancement filter configured to emphasize the formant frequency; an inverse filter configured to be applied to the input audio signal to obtain an excitation signal; the enhancement filter configured to be applied to the excitation signal to produce a first modified voice signal, the enhancement filter further configured to be applied to the input voice signal to produce a second modified voice signal; a combiner configured to combine at least a portion of the first modified voice signal with at least a portion of the second modified voice signal to produce a combined modified voice signal; and an output module configured to output an audio signal based on the combined modified voice signal for playback.
17. The system of claim 13 , further comprising a temporal enveloper shaper configured to apply a temporal enhancement to the combined modified voice signal at least by increasing a slope of a temporal envelope in the combined modified voice signal.