Question

Why do we don't hear sound below 20Hz and above 20,000Hz?

Answer 1

In general terms, the frequency range for human hearing is about 20 Hz - 20,000 Hz (at least in “normal hearing young adults”). The response of the ear is governed, in part, by the mass and elasticity of the eardrum, muscles and ligaments, bones, and fluid and structures in the inner ear. Elasticity opposes low frequency sounds, while mass opposition increases as frequency increases. So both mass and elasticity set limits for frequency range. As an interesting aside, an object will resonate at a frequency where elastic opposition has decreased and mass opposition isn’t too high. For human ears, its about 2000–4000 Hz. So those frequencies are amplified for us…important, because that’s the range where speech sounds are heard to maximize understanding of speech.