The subjective equivalence of sinusoidal and random whole-body vibration in the sitting position (an experimental study using the ‘floating reference vibration’ method)

Abstract

An experimental technique known as the ‘floating reference’ method was developed to compare the subjective response of seated subjects to sinusoidal vibrations in the range l-10Hz with those produced by narrow-band random vibration (Gaussian distribution) centred on the same frequencies. Male and female subjects were asked to adjust the r.m.s. amplitude of each test vibraiion until it produced an overall sensation equivalent to that caused by a reference vibration. The frequency content and r.m.s. values of the random stimuli measured on the seat attachment plate are representative of vibration environments associated with earth-moving machines and tractors for agricultural and forestry use.

The results have a small dispersion and show that subjects generally appear to be slightly more sensitive to random excitation than to sinusoidal (approximately I dBwhen averaged over the range 1-10 Hz). This difference of sensitivity decreases at higher frequencies, but was observed in all three translational directions of fore-and-aft, lateral and vertical motion at frequencies below 6 Hz.

The equivalent sensation contours derived from these experiments relate only roughly to the weighting curves enshrined in the Standard ISO 2631, particularly for the fore-and-aft axis.

Additional information

Notes on contributors

P. DONAT

Present address; National Institute of Agricultural Engineering, Silsoe, Beds, England