The Acoustics of snoring

Snoring is a prevalent disorder affecting 20-40% of the general population. The mechanism of snoring is vibration of anatomical structures in the pharyngeal airway. Flutter of the soft palate accounts forthe harsh aspect of the snoring sound. Natural or drug-induced sleep is required for its appearance. Snoring is subject to many influences such as body position, sleep stage, route of breathing and the presence or absence of sleep-disordered breathing. Its presentation may be variable within or between nights. While snoring is generallyperceived as a social nuisance, rating of its noisiness is highly subjective and, therefore, inconsistent. Objective assessment of snoring is important to evaluate the effect of treatment interventions. Moreover, snoring carries information on the site and degree of obstruction of the upper airway. If evidence for monolevel snoring at thelevel of the soft palate is provided, the patient may benefit frompalatal surgery. These considerations have inspired researchers to scrutinize the acoustic characteristics of snoring events. Similarlyto speech, snoring is produced in the vocal tract. Because of this analogy, existing techniques for speech analysis have been applied toevaluate snoring sounds. It appears that the pitch of the snoring sound is in the low frequency range ( 500 Hz). To evaluate acoustic propertiesof snoring, sleep nasendoscopy is often performed. Recent evidencesuggests that the quality of snoring is markedly different in drug-induced sleep as compared with natural sleep. Most often, palatal surgery alters sound characteristics of snoring, but is no cure for this disorder. It is uncertain whether the perceived improvement afterpalatal surgery, as judged by the bed partner, is due to an alteredsound spectrum. Whether some acoustic aspects of snoring, such as changes in pitch, have predictive value for the presence of obstructive sleep apnea is at present not sufficiently substantiated.