THE ACOUSTIC PROPERTIES OF SNORES

This study was undertaken in an attempt to characterize the acoustic p roperties of snoring sounds in the time and frequency domains, and to correlate between these properties and the mechanical events underlyin g their production. Three experimental set-ups were used: 1) Dog model - six mongrel dogs, in which partial upper airway obstruction was cre ated by an implanted supraglottic balloon. Flow, supraglottic pressure , and snoring sounds were recorded during different degrees of obstruc tion. Fifteen to 20 snores from each dog (total 100 snores) were analy sed. 2) Simulated human snores - Six simulated snores from each of fou r subjects were recorded in two locations (trachea and ambient) with s imultaneous airflow, and their correlations examined. 3) Snoring patie nts - snores were recorded with an ambient microphone from nine subjec ts with ''heavy'' snoring and no obstructive sleep apnoea (OSA). Forty to 50 snores from each subject were analysed (total of 400 snores). T he snoring sound was analysed in the time (time-expanded waveform) and frequency (power spectrum) domains. After analysing these snores, we were able to identify two dominant patterns which are distinctly diffe rent from each other: the ''simple-waveform'' and the ''complex-wavefo rm''. The complex-waveform snore is characterized by repetitive, equal ly-spaced, train of sound structures, starting with a large deflection followed by a decaying amplitude wave. In the frequency domain, it is characterized by multiple, equally-spaced peaks of power (comb-like s pectrum). Simple-waveform snores have a quasi-sinusoidal waveform, wit h a range of variants, and almost no secondary internal oscillations. Their power spectrum contains only 1-3 peaks, of which the first is th e most prominent. We developed a mathematical representation of these waveforms, which is presented along with its implications. The complex -waveform snores result from colliding of the airway walls and represe nt actual brief airway closure. Simple-waveform snores are of higher f requency and probably result from oscillation around a neutral positio n without actual closure of the lumen.