Comparison of the subjective intensity of sinusoidal, multifrequency, and random whole-body vibration.

An intensity matching technique was used in two experiments to test the independent component method for evaluating complex vibration environments, recommended by current vibration standards; In the first experiment, seated subjects adjusted the intensity of a 25 Hz sinusoid to match the subjective intensity of 11, 17, 40, and 63 Hz simusoids, presented either singly or in combinations of two, three, or four frequencies. In the second experiment, 25 Hz was again used to match the subjective intensity of third octave bands of random vibration with center frequencies of 16, 20, 25, 31;5, and 40 Hz, presented either singly or in combinations of two, three, or four bands. The results showed that the acceleration of the matching response increased significantly as the number of sinusoids or third-octave bands in the stimulus increased; These findings indicate that the independent component evaluation method will underestimate the severity of complex vibration environments, and suggest that their perceived intensities may be more accurately reflected by the weighting technique included in the standards as an alternative evaluation method.