Frequency response of the skin on the head and neck during production of selected speech sounds.

Vibrations within the vocal tract during speech are transmitted through tissue to the skin surface and can be used to transmit speech. Achieving quality speech signals using skin vibration is desirable but problematic, primarily due to the several sound production locations along the vocal tract. The objective of this study was to characterize the frequency content of speech signals on various locations of the head and neck. Signals were recorded using a microphone and accelerometers attached to 15 locations on the heads and necks of 14 males and 10 females. The subjects voiced various phonemes and one phrase. The power spectral densities (PSD) of the phonemes were used to determine a quality ranking for each location and sound. Spectrograms were used to examine signal frequency content for selected locations. A perceptual listening test was conducted and compared to the PSD rankings. The signal-to-noise ratio was found for each location with and without background noise. These results are presented and discussed. Notably, while high-frequency content is attenuated at the throat, it is shown to be detectable at some other locations. The best locations for speech transmission were found to be generally common to males and females.