Biomedical subjects
Publications and source records attributed to C J Keemink.
Based on a VME system, a low-cost video system has been developed for recording human motion. The paper describes the algorithm which is used for the recordings. The video system makes it possible to track in real time up to six markers on the body, sampled at a 50 Hz rate.
Investigations have been carried out in order to determine (1) the sensitivity of the two types of skin for sinusoidal mechanical vibrations under different stimulation conditions, and (2) the sensitivity of the skin for amplitude modulations. Maximum sensitivity was found around 200 Hz, with a threshold of 0.03 microns RMS for the glabrous skin of the inner side of the hand under a static force of at least 0.5 N. The sensitivity of the hairy skin of the arm was 12 dB less (static force at least 3 N). The sensitivity increased with increasing contractor area. Maximum modulation sensitivity was found for sinusoidal carriers between 200 and 400 Hz and extended from modulation frequencies of 1 Hz up to 200 Hz (depending on carrier frequency) at a frequency-independent modulation depth of about 0.1. It was concluded that it is certainly possible for the skin to detect the slow amplitude fluctuations of speech signals as a support for lipreading. Attention was paid to the best way of extracting the envelopes from the speech signal and their presentation, as an amplitude modulation, to the skin.
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