ACCEPTABLE LEVELS OF TONAL AND BROAD-BAND REPETITIVE AND CONTINUOUS SOUNDS DURING THE PERFORMANCE OF NONAUDITORY TASKS

Three groups of 24 subjects were exposed to a 1000-Hz tone or broad ba nd noise in a sound chamber. During the exposures subjects were engage d in an easy reaction time test or a difficult grammatical reasoning t est. For each exposure and work subjects adjusted the noise to a toler ance level defined by its interference with task performance. During t he simple reaction-time task significantly higher sound-pressure level s were accepted than during the reasoning test. At the tonal exposure, much lower levels were accepted than during the exposure to broad-ban d noise. For continuous sound exposures much higher levels were accept ed than for noncontinuous exposures. For tonal exposures the differenc e was approximately 5 dB, for the broad-band exposures approximately 9 dB. In a separate study the effects of the noncontinuity of the noise and pauses were analysed. The raised annoying effect of the noncontin uous noise was not more affected by the noncontinuity of the noise per iods than by the noncontinuity of the pauses. The results imply that t he annoying reactions to the sound will be increased for repetitive no ise and that the reaction is highly influenced by the over-all noncont inuity of the exposure.