Abstract
In information transmission via vibrotactile sensation, undesirable fluctuations of sensation are sometimes observed according to the change of conditions of the skin and the vibrator.
In order to make the factors of these instabilities clear, studies were undertaken on 1) variations of mechanical parameters in vibration, mechanical resistance, mass and stiffness of skin due to activity change of muscles beneath the skin, 2) the effect of contact force of a vibrator with the skin on the parameters and 3) ambient temperature characteristics of a small loud speaker which is sometimes remodeled as the vibrator.
Mechanical parameters of the skin were calculated from mechanical dynamic impedance loci of a vibrometer which was positioned on the middle of extensor muscles of forearm with a strip of double-face adhesive tape. The contacting area was 0.50 cm2. The loci were drawn on a X-Y recorder by plotting in-phase and quadrature components of output signal from the vibrometer for drive current, a vector analyzer having been used to divide the signal into two components. Activities of muscles were measured by EMG.
The results show that mechanical resistance, mass and stiffness of the skin increase according to the increment of contact force. Activity change of muscles from 0 to 420, μV-mean induces the increment of stiffness of skin from 80 to 350 N/m. The stiffness of a small loud speaker is sensitive to ambient temperature and the speaker which has been casually remodeled as a vibrator for information transmission is not suitable for a stable information transmitter.
