Effect of age and gender on LP smoothed spectral envelope

It is well known that linear prediction (LP) analysis suffers from drawbacks that are especially manifested during voiced segments of speech. The first drawback is in the form of its inherent error cancellation property and the second drawback is that the poles, as estimated by LP analysis, generally move in the direction of pitch harmonics. These two drawbacks make this analysis sensitive to the fundamental frequency of speaker. In this paper, this sensitivity is analyzed by computing a distance measure between signal power spectrum and spectral envelope estimated by LP analysis at spectral peaks. It is shown that this distance shows the same trend as the fundamental frequency of the speaker, i.e. higher the pitch frequency, greater is the distance between two spectra. This combined with the observation that children, adult male and adult female speaker classes have fundamental frequencies in significantly different ranges, makes this distance an obvious choice for discrimination among these three classes. An experimental framework is set-up for this classification task and the results (about 85% and 93% age and gender classification rates) clearly validate this hypothesis