Speech Reinforcement: Hearing

This article is part of a series; see Speech Reinforcement.

The final part of the audio signal path is the ears, and the audio stimulus is then processed by the brain.

Frequency

A person with exceptional hearing can detect frequencies in the range of 20 Hz to 20 kHz.
There are several types of hearing loss with varying characterisics; see Wikipedia: Sensorineural hearing loss.
Noise-induced hearing loss usually occurs as a notch primarily at 4 kHz and to a lesser extent 3 kHz and 6 kHz, then later at lower frequencies (500 Hz, 1 kHz, or 2 kHz).1
Presbycusis, or age-related hearing loss, affects the very high frequencies and can progress down as far as the 2-4 kHz range.2
If you do not have hearing loss, you can hear simulated mild and moderate hearing loss by listening to the samples at the Henry Ford Hearing Loss Simulator (best with earbuds or earphones).

“Any sound that reaches our ears within 50-80 milliseconds of the original sound gets interpreted by our brains as the original sound”.3 Consequently, sound received during that timeframe damages the quality of the original sound.