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This paper presents a detailed study of the vibrations on the surface of the neck during a vocalization of predefined fundamental frequency and intensity. This study was carried out as part of a wider investigation into the use of laryngeal vibrations as a channel of communication. Another potential application of this study is in identifying a suitable location for a hands-free electro-larynx for laryngectomees.
An analog accelerometer, with dimensions 5x5x1.6mm and of mass 80mg, was used to perform the measurements. It was connected to a 12-bit analog-to-digital converter via single strands of insulated wire with a diameter of 100μm. The resulting low inertia of the measuring device minimized the effect of the measuring device on the phenomenon under investigation. The analog-to-digital converter simultaneously sampled the accelerometer output and a pre-amplified audio signal from a microphone.
This preliminary study was carried out on two able-bodied male subjects. Measurements were taken from forty-five preselected locations on the neck. Each subject made the vowel sound /i/ (long ‘e’) at three different fundamental frequencies, 150Hz, 200Hz and 250Hz. Once the vocal pitch and intensity matched pre-defined target values, a 200ms recording was captured by a virtual instrument designed in LabVIEW.
A detailed map of skin surface vibration amplitude during vocalization is presented and suitable locations for laryngeal vibration measurement are identified. Further more, detailed analysis of the time varying acceleration function at various measurement positions reveals a rich and complex source of information. Novel visualizations of these signals are presented.
Nolan, Mark, Madden, Brian, Burke, Edward: Accelerometer Based Measurement for the Mapping of Neck Surface Vibrations During Vocalized Speech. Engineering in Medicine and Biology Society, 2009, EMBC 2009, Annual Internation Conference of the IEEE