Palatal snoring identified by acoustic crest factor analysis

The differentiation of palatal from non-palatal snoring is very important f or ENT surgeons trying to determine whether palatal surgery would be curati ve. At present sleep nasendoscopy is the accepted method. Palatal vibration produces marked modulation of sound loudness at low frequ ency (below similar to 100 Hz). We calculate a crest factor for the sound w aveform (ratio of peak to root mean square (rms) value in any given epoch), as a measure of the degree of modulation. Free-field snore sounds were recorded from 11 supine adult patients under i ntravenous sedation (midazolam), using a digital tape recorder. Recordings were transferred to a PC (sampling frequency 11 kHz), and analysed using co de written by us. Direct visual confirmation of the site of snoring was gai ned from simultaneous sleep nasendoscopy, taken as the gold standard. In si x patients the dominant site was the soft palate. The non-palatal group (fi ve patients) comprised one epiglottic, two hypopharyngeal and two tongue ba se snorers. The crest factor was found to be significantly higher for palatal snorers ( p < 0.01, Student-t or Mann-Whitney tests). Furthermore, palatal could be d istinguished from non-palatal snorers on the basis of crest factor alone in all 11 cases, making this a promising non-invasive diagnostic technique.