Exposure data of LFN causing subjective complaints in relation to the hearing threshold (mean value of Robinson et al. 1956, Corso 1958, Yeowart et al. 1967 and 1974, Whittle et al. 1972, Landstrï¿½m et al. 1983, Verzini et al. 1999 (see Figure 1)) and to the threshold of aural pain.