A computer-implemented process for estimating speech quality of an audio frame in a single-channel audio signal comprising human speech components, the process comprising: inputting a frame of the audio signal; estimating the fundamental frequency of the inputted frame; transforming the inputted frame from the time domain into the frequency domain to produce a frequency spectrum of the frame; computing magnitude and phase values for the frequencies in the frequency spectrum of the frame corresponding to each of a prescribed number of integer multiples of the fundamental frequency; computing a subharmonic-to-harmonic ratio - SHR - for the inputted frame based on the computed magnitude and phase values; synthesizing a representation of a harmonic component of the inputted frame based on the computed SHR, along with the fundamental frequency and the magnitude and phase values; computing a non-harmonic component of the inputted frame based on the magnitude and phase values, along with the synthesized harmonic component representation; computing a harmonic to non-harmonic ratio - HnHR - based on the synthesized harmonic component representation and the non-harmonic component; and designating the computed HnHR as an estimate of the speech quality of the inputted frame in the single-channel audio signal; wherein the process action of computing the SHR for the inputted frame based on the computed magnitude and phase values, comprises computing the quotient of a summation of the magnitude values computed for each frequency in the frequency spectrum of the frame corresponding to each of the prescribed number of integer multiples of the fundamental frequency divided by a summation of magnitude values computed for each frequency in the frequency spectrum of the frame corresponding to each of the prescribed number of integer multiples of the fundamental frequency less 0.5. inputting a frame of the audio signal; estimating the fundamental frequency of the inputted frame; transforming the inputted frame from the time domain into the frequency domain to produce a frequency spectrum of the frame; computing magnitude and phase values for the frequencies in the frequency spectrum of the frame corresponding to each of a prescribed number of integer multiples of the fundamental frequency; computing a subharmonic-to-harmonic ratio - SHR - for the inputted frame based on the computed magnitude and phase values; synthesizing a representation of a harmonic component of the inputted frame based on the computed SHR, along with the fundamental frequency and the magnitude and phase values; computing a non-harmonic component of the inputted frame based on the magnitude and phase values, along with the synthesized harmonic component representation; computing a harmonic to non-harmonic ratio - HnHR - based on the synthesized harmonic component representation and the non-harmonic component; and designating the computed HnHR as an estimate of the speech quality of the inputted frame in the single-channel audio signal; wherein the process action of computing the SHR for the inputted frame based on the computed magnitude and phase values, comprises computing the quotient of a summation of the magnitude values computed for each frequency in the frequency spectrum of the frame corresponding to each of the prescribed number of integer multiples of the fundamental frequency divided by a summation of magnitude values computed for each frequency in the frequency spectrum of the frame corresponding to each of the prescribed number of integer multiples of the fundamental frequency less 0.5.