Infrasound, Its Sources and Its Effects on Man

Infrasound, sinusoidal pressure variations from 0.1 to 20 Hz, is somewhat more complicated to measure and analyze than sound of higher frequency. But the most common error in analyzing infrasound is not to also measure the higher frequency sounds and then interpret these sounds with respect to their effects on humans. Generally, where there is intense infrasound, there are also intense sounds above 20 Hz; and these are the sounds that cause adverse human effects. At sufficient intensity infrasound is audible, but is easily masked by higher frequency sound. Infrasound does not often occur at levels that are harmful or even audible to man. Thus infrasound exposure is not one of mankinds more pressing environmental problems.