Perturbation-free measurement of the harmonics-to-noise ratio in voice signals using pitch synchronous harmonic analysis

The measurement of the harmonics-to-noise ratio (HNR) in speech signals giv es an indication of the aperiodicity of the speech waveform. This may be du e to the presence of jitter, shimmer, additive noise, waveshape change, or some unknown combination of these factors. In order to estimate the HNR as a measure of the additive noise component only, the contaminating effects o f the other contributory components must first be removed. A pitch synchron ous harmonic analysis is proposed to overcome this problem. The procedure t akes advantage of the rime scale compression-frequency expansion property o f the Fourier series in order to eliminate jitter and shimmer. Successive s pectra an added by harmonic number as opposed to frequency location, and pe rturbation is removed due to the fact that the relative heights of the harm onic components remain the same for scaled signals. The technique is examin ed on synthetically generated voice signals. A discussion of the results is given in terms of human voice signals, characterization of jitter, vocal t ract filtering effects, perturbation mechanisms, nonlinear dynamics, and th e possibility of developing the method for use with inverse filtering strat egies. (C) 1999 Acoustical Society of America. [S0001-4966(99)01305-3].