Abstract
We recorded swallowing sounds, including characteristic sharp click-like sounds, through the ear (intra-aural swallowing sounds) using a small lavalier microphone in 10 normal adults with no swallowing disorders or ear diseases. Simultaneous recordings of the intra-aural swallowing sounds and nasopharyngeal endoscopic findings revealed that the characteristic click-like sounds with high-frequency spectra came at the beginning of the pharyngeal phase of swallowing. This finding strongly suggested the click-like sounds coincide with the Eustachian tube's quick open-close movements. Intra-aural swallowing sounds are easy to record using low cost and relatively uncomplicated equipment. Also, among intra-aural swallowing sounds, the characteristic click sound is relatively easy to identify both by sound spectrographic processing and with repeated listening. Moreover, by using this click sound as an indicator of a certain point of swallowing (opening of the Eustachian tube), analyses of swallowing activity can be performed with considerable precision in time-domain. Although much additional study remains to be carried out, such as investigating the influences of aging, tubal function and dysphagia, our findings suggest that recording of intra-aural swallowing sounds can be one of the most useful and non-invasive methods for screening of dysphagia and precise analysis of dynamics of swallowing.
