What is the hearing span of humans?

The human hearing span typically ranges from about 20 Hz to 20,000 Hz (20 kHz). Frequencies below 20 Hz are considered infrasound, while those above 20 kHz are classified as ultrasound. Most adults, however, primarily hear best between 1,000 Hz and 5,000 Hz, which corresponds to the frequencies of human speech. Sensitivity to higher frequencies tends to decline with age.