Transmission of hand-arm vibration to the head.

A "tooth impression" was devised to measure head vibration. The vertical head vibration of four subjects was measured with the tooth impression during exposure of the hand to vertical sinusoidal vibration at acceleration levels of 3.15, 10.0, and 31.5 m/s2 root mean square in the range of 8-200 Hz. While in a standing position, the subjects pulled the vibrating handle upward at a force of 5 kg with the elbow joint stretched during the tests. The measurement was repeated twice. The difference between the two measurements was within 3 dB, a level which suggests that this method has good reproducibility. The vibration transmitted to the head was the greatest in the range of 12.5-16 Hz, and the attenuation was about 20 dB. Head vibration decreased by approximately 15 dB per octave at frequencies above 20 Hz as the frequency increased. When the excitation level was increased by 10 dB, the head vibration increased by about 8 dB.