[The effect of low frequency noise on human mental performance]

There is a growing body of data showing that low frequency noise (LFN) defined as broadband noise with dominant content of low frequencies (10-250 Hz) differs in its nature from other noises at comparable levels. The aim of this study was to assess the influence of LFN on human mental performance. Subjects were 193 male paid volunteers. They performed standardized tests: the Signal Detection Test (test I), the Stroop Color-Word Test (test II), and two sub-tests of the General Aptitude Test Battery, i.e. the Math Reasoning Test (test III) and the Comparing of Names Test (test IV). Three different acoustic conditions were used in the experiment the background laboratory noise of about 30 dB(A), LFN and the broadband noise at comparable db(A) levels of 50 dB. The study subjects were assigned randomly to varied experimental conditions. After the test session, the subjects completed a questionnaire aimed at rating the subjective annoyance of exposure conditions during the tasks, and assessing individual sensitivity to noise in general and LFN in particular. The main effects of exposure and/or noise sensitivity on the tests' results or their interaction were found in three of the four tests performed (tests I, II and IV). The tendency towards weaker results in low frequency noise compared to other conditions was observed in persons classified in test II as more sensitive to LFN (higher value of reading interference). The significant effect of both exposure and sensitivity to noise on annoyance rating during test performance was also noted. The annoyance of LFN and reference noise was rated higher than that of background noise. LFN at 50 dB(A) could be perceived as annoying and adversely affecting mental performance (concentration and visual perception), particularly in persons sensitive to LFN.