Salt, Lichtenhan, Responses of the Inner Ear to Infrasound

Alec N. Salt & Jeffery T. Lichtenhan
Fourth International Meeting on Wind Turbine Noise, Rome April 2011

Unweighted sound measurements show that wind turbines generate high levels of infrasound. It has been wrongly assumed that if subjects cannot hear the infrasound component of the noise then they cannot be affected by it. On the contrary, the mammalian ear is highly sensitive to infrasound stimulation at levels below those that are heard. Most aspects of responses to infrasound are far from well established.

Measurements made within the endolymphatic system of the cochlea show responses that become larger, relative to measurements made in perilymph, as frequency is lowered. This suggests that endolymphatic responses to infrasound are enhanced in some manner. For high-frequency sounds, acoustic stimuli in the ear are summed.

In contrast, the inner ear’s responses to infrasound are suppressed by the presence of higher frequency stimuli. The complexity of the ear’s response to infrasound leads us to the conclusion that there are many aspects that need to be better understood before the influence of wind turbine noise on the ear can be dismissed as insignificant.

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