The effects of feedback filtering on nasalization in normal and hypernasal speakers

Two groups of subjects, one with normal speech and one with hypernasal speech, spoke while hearing their voices unfiltered, low-pass filtered with cut-off frequencies of 1000, 500, and 300 Hz and high-pass filtered with cut-off frequencies of 500, 1000, and 2000 Hz. Measurements of nasalization were made with a miniature accelerometer attached to the side of the subject's nose. Both groups of subjects decreased nasalization when hearing their voices low-pass filtered with a cut-off frequency of 300 Hz. This decrease was statistically significant. The results were interpreted as supporting the hypothesis that nasalization is under feedback control.