Individual differences in low-frequency noise perception

Standards on hearing like threshold and equal-loudness-level contours show the normal hearing sensitivity at low frequencies as following smooth slopes. However, recent non-invasive measurements of the forward middle-ear transfer function (FMETF) reveal a "resonance feature" seen as 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 was measured for five subjects and an equal-loudness contour (ELC) was measured in a fine frequency grid 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 lowfrequency sound that is not audible to other people.