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Tension of the forehead increases as a response to unpleasant stimuli. In three experiments EMG activity in corrugator muscle was measured to test this response as an indicator of noise annoyance. In Exp. 1 (n = 24) monotonic sound level-response functions were obtained for four levels of 100- and 1000-Hz tones. In Exp. 2 (n = 20) recordings were made during work with a simple and a difficult task in a group of women and a group of men. Larger responses were obtained during the difficult task, especially during noise exposure. The response was much larger for the women. Exp. 3 (n = 24) showed that the sex difference was unaffected by a correction for differences in maximum level of corrugator response. Rated annoyance was a linear function of log EMG.

Different ways of assessing low frequency noise below the level of hearing damage to predict noise annoyance are treated. Three methods for classification of low frequency noise are tested. Some assessment methods, e.g. low frequency noise ratings (LFNR), frequency weightings A - D, the difference dB(C) - dB(A) and Zwicker loudness, are presented and evaluated regarding their relation to rated annoyance. Low frequency noise groups were selected out of 338 recordings from different occupational environments, e.g offices, laboratories, manufacturing premises, etc. The annoyance ratings were made on a graphic rating scale. The annoyance ratings corresponding to the recordings were correlated to the different low frequency noise measurements. Correlations between different low frequency noise measures and annoyance ratings are presented. None of the methods that are evaluated seems to fit better than the others for assessment of low frequency noise annoyance. A conclusion drawn is that when assessing low frequency. noises, the usual methods should be handled with care.