Combined effects of broadband noise and complex waveform vibration on cognitive performance.

The performance of 12 subjects was measured on a Complex Counting Task during exposure to each of four experimental conditions for a duration of 30 min. Two levels of noise, 65 dBA and 100 dBA, were presented both with and without 0.36 R.M.S. Gz sum-of-sines vibration. Combined 100 dBA noise and vibration produced less adverse effects than the vibration combined with 65 dBA noise. This result agrees with out previous studies using tracking tasks. However, two effects were demonstrated that had not been obtained previously. First, a clearcut adverse effect of vibration on the Counting Task was obtained. Second, an adverse effect of 100 dBA noise on the counting task was demonstrated. Previously, a 110 dBA noise was required to adversely affect tracking performance.