Brain’s Frequency Following Responses to Low-Frequency and Infrasound

Complaints and awareness about environmental low-frequency (LF) noise infrasound (IS) have increased in recent years, but knowledge perceptual mechanisms is limited. To evaluate the use of brain’s frequency-following response (FFR) as an objective correlate individual sensitivity to IS LF, we recorded FFR monaurally presented (11 Hz) LF (38 tones over a 30-phon range for 11 subjects. It was found that 11-Hz FFRs were often significant already at ~0 phon, steeply grew 20 saturated above. In contrast, 38-Hz growth relatively shallow continued 60 phon. Furthermore, same loudness level (30 phon), strength significantly larger (4.5 dB) than 38 Hz, possibly reflecting higher phase synchronization across auditory pathway. Overall, unexpected inter-individual variability well qualitative differences between measured functions typical make interpretation difficult.