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The relative discomfort of noise and vibration: effects of stimulus duration

How noise discomfort and vibration discomfort depend on duration has not previously been compared. For five durations (2, 4, 8, 16 and 32 s), the subjective equivalence of noise and vibration was investigated with all 49 combinations of 7 levels of noise and 7 magnitudes of whole-body vertical vibration. The rates of increase in discomfort with increasing duration were similar for noise and vibration, whereas they are currently assumed to be 3 dB per doubling of noise duration and 1.5 dB per doubling of vibration duration. The discomfort caused by low levels of noise was masked by high magnitudes of vibration, and the discomfort caused by low magnitudes of vibration was masked by high levels of noise. As stimuli durations increased from 2 to 32 s, the influence of vibration on the judgement of noise discomfort decreased, whereas the influence of noise on the judgement of vibration discomfort was unchanged. Practitioner Summary: For predicting the relative discomfort caused by steady-state noise and steady-state vibration over durations from 2 to 32 s, the combination of average measures of sound and vibration (e.g. sound pressure level and root-mean-square acceleration) provide more accurate estimates than the combination of the principal standardised ‘dose’ measures (e.g. sound exposure level and vibration dose value).