Fig. 1.
A single swallow simultaneously recorded with both a microphone and dual axis accelerometer [21]. One can see obvious differences between sound and vibratory signals as well as different vibration directions.
(a) Time domain recording. Top figure: Microphone, Middle figure: Anterior-Posterior direction of the accelerometer, Bottom figure: Superior-Inferior direction of the accelerometer. This figure has been previously published by BioMed Central in [21].
(b) Corresponding power spectral density estimates of (1a)