The Effect of Phase of Differential Vertical Vibration at the Seat and Feet on Discomfort

✍ Scribed by H.-K. Jang; J.M. Griffin

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 142 KB
• Volume: 223
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.1999.2156

✦ Synopsis

This experiment investigated whether the discomfort of seated subjects exposed to vertical vibration was in¯uenced by the relative phase between vibration at the seat and the feet. Twelve seated subjects were exposed to sinusoidal 4 Hz vibration by means of two vibrators, one under the seat and the other under a footrest. A total of seventy combinations of vibration stimuli with seven phases (0, 30, 60, 90, 120, 150, 180 ) between the seat and the footrest and ®ve acceleration levels (0Á25, 0Á4, 0Á63, 1Á0, 1Á6 ms À2 r.m.s.) were presented to subjects in two postures (with and without thigh contact with the seat). The subjects judged that the dierential vibrations with greater phase dierence caused greater discomfort. The subjects were most sensitive to phase changes at low magnitudes of vibration and with thigh contact. In the equation, c = Kf n , between the discomfort, c, and the magnitude of vibration, f, the exponent n had a maximum of 1 Á 48 with thigh contact and 1 Á 24 with no thigh contact, and decreased to approximately 1Á0 with increasing phase between the seat and the feet. The results indicate that vibration discomfort is in¯uenced by the phase between the seat and the feet, but that the eect depends on the magnitude of vibration and the posture of the body.