Effects of combined noise and vibration on annoyance

Abstract Four experiments were conducted to investigate the combined effects of noise and vibration on rated intensity and annoyance. Four levels of vibration and noise (none, low, medium and strong) were presented to subjects, in every possible combination. These levels were chosen according to those which were measured in the flats where the stimuli were recorded. The background noise was low to simulate the appropriate noise level. Each experiment was carried out with different subjects. Two signals with different characteristic time histories were investigated, a passing tram and a hammermill. The intensity and annoyance were measured on graphic scales ranging from 0 to 9. The results show that vibration influences the evaluation of noise annoyance, especially if one asks for the total annoyance. The assessment of the combined stimuli is dominated by the noise level, but it is also influenced by the simultaneously perceptible vibration. All of these results were highly significant. On the other hand, only the assessment of the vibration caused by the tram is significantly influenced by a simultaneous noise level ranging up to 60 dB(A). According to these experiments, the gradient for the subjective equivalence of noise and vibration is only half as high as that estimated by Howarth and Griffin in similar investigations for higher noise levels and higher magnitudes of vibration.