Individual differences in low-frequency noise p erception.

Standards on hearing like threshold and equal-loudness-level contours show the normal hearing sensitivity at low frequencies as smooth curves. However, recent non-invasive measurements of the forward middle-ear transfer function (FMETF) reveal a resonance feature seen as a dip and a peak in the FMETF where the slope changes approx. 6 dB/octave (around 40-65 Hz depending on person). The change in slope is attributed to the shunting effect of the helicotrema. A preliminary study has been carried out in order to see if this resonance feature measured objectively is also found in perceptual data. The FMETF and an equal-loudness contour (ELC) were measured for five subjects with a fine frequency resolution from 20 Hz to 100 Hz. For two subjects a clear resonance feature was seen in the ELC, but it was not evident in the data for the remaining subjects. This means that some people have a narrow frequency range where they are more sensitive and a narrow range where they are less sensitive compared to the standards. Since the frequency range is subject dependent this could explain why some people are annoyed by a low-frequency sound that is not audible to other people. a Email address: cp@acoustics.aau.dk b Email address: t.marquardt@ucl.ac.uk