They're blowing their spare tires. In the absence of loud noises, hearing doesn't appear to deteriorate much with age. For example, deep in the Sudan bush, a primitive tribe lives in a quiet environment, surrounded by swamps and the White Nile River. A study done in the early 1960s found that people of any age in the tribe had hearing superior to that of a comparison group of American farmers. Furthermore, the old people heard as well as the young.
Modern life is much harder on hearing.
Noise is measured in decibels. The higher the decibel, the louder the noise. The accompanying noise scale shows the loudness of common sounds. The louder the noise, the shorter the time it takes to hurt your hearing. Your ears can endure 90 decibels of noise, such as a lawn mower, for about eight hours before damage occurs.