The last exercise may be rather difficult. He cut pieces off the other end and blew to demonstrate that, as the straw becomes shorter, the pitch of the sound goes up. Consequently, it is routine to amplify the low frequencies on stereo systems. Many teachers cannot hear well at frequencies much beyond 8 KHz , whereas most students can detect frequencies up to 20 KHz . Between ages 10 and 20, males begin to show reduced high-frequency auditory sensitivity relative to females.
Women continue to demonstrate better hearing than men into advanced age.
These gender differences are probably due to greater exposure of males to noise rather than to their inherent susceptibility to its effects. This rough correspondence also works pretty well for animals. He also commented on transmission of sound in the oceans, which enables marine mammals to communicate over great distances. Acoustic thermometry, however, capitalizes on the presence of sound channels present in the deep sea capable of trapping and transmitting sound over very long distances. The channels are created by the variation of pressure and temperature with depth.