Normal Hearing Variants

Question

Answer

We are unaware of a physiological cause for this configuration. The only explanation we could come up with relates to test environment and the transducers that were used. If the testing was not performed in a sound-treated room, ambient room noise could have the effect of elevating thresholds for low and mid frequencies (because that is where the energy is more likely to be located in ambient room noise) with less of an effect at higher frequencies. That would not be inconsistent with the pattern you describe. If insert earphones were used, it is less likely that this pattern would be observed because they tend to be better attenuators of ambient room noise, compared to supra-aural earphones. If supra-aural earphones were used or if the testing was done in the sound field, then perhaps ambient room noise caused the elevations in threshold.


Michael P. Gorga, Ph.D., directs the clinical sensory physiology laboratory at the Boys Town National Research Hospital in Omaha, Nebraska. His work has focused on objective tests of auditory function, including the use of auditory brainstem response and otoacoustic emission measurements in universal newborn hearing screening and in quantifying the magnitude and configuration of hearing loss. His more recent work is focused on suprathreshold measures of auditory function in normal and impaired ears.