Sagot :
Humans can generally sense sounds at frequencies between 20 and 20,000 cycles per second, or hertz (Hz)—although this range shrinks as a person ages. Prolonged exposure to loud noises within the audible range have long been known to cause hearing loss over time. But establishing the effect of sounds with frequencies under about 250 Hz has been harder. Even though they're above the lower limit of 20 Hz, these low-frequency sounds tend to be either inaudible or barely audible, and people don't always know when they're exposed to them