A study of the subjective equivalence of noise and whole-body vibration

An experiment has been conducted to determine the subjective equivalence of 1000 Hz pure tone noise and 10 Hz sinusoidal whole-body vertical vibration. Each of 20 male subjects was exposed to all 64 possible combinations of 8 levels of noise (65 dB to 100 dB SPL) and 8 levels of vibration (0·20 m/s² r.m.s. to 1·2 m/s² r.m.s.). The noise was presented via circumaural headphones and the vibration exposure was by means of a flat hard seat. The method of constant stimuli was used. Both stimuli were presented simultaneously for a period of ten seconds and subjects were asked to indicate whether, if they were to be presented with the combination again, they would prefer that the noise or the vibration should be reduced.It was concluded that the subjects were relatively self-consistent and that the major source of variability was due to intersubject differences. The conditions for equivalence for 50% of the subjects ranged from about 0·2 m/s² r.m.s. at 69 dB to 1·2 m/s² r.m.s. at 94 dB. The results are presented in a form that enables an estimate to be made of the percentage of subjects who prefer reduced noise or vibration at any of the given combinations of the two stimuli. Further studies to extend the range and establish the general applicability of these results are suggested. It is considered that such results could be employed as a guide to reducing either the noise or the vibration in some environments.