The diagram to the right shows the range of sounds, in frequency and sound pressure level, that humans can hear.
Humans can hear frequencies as low as 20 Hz and as high as 20 kHz. There are significant inter-subject differences, though. Our ability to hear the highest frequencies is lost as we age. Hearing damage, due to injury or exposure to excessive levels of noise, affects what we can hear.
All frequencies are not heard equally. In the mid-frequency band, say between 500 Hz and 5 kHz, sounds at sound pressure levels of about 0 dB are audible to young, healthy ears. At lower and higher frequencies, sounds must be louder to be audible. For example, a sound pressure level of 40 dB is needed for sound to be audible at 50 Hz. The bottom curve of the area “Audible range” shown in orange is the threshold of hearing.
At much higher sound pressure levels, at about 120 dB, sound is not so much heard as felt. These levels, indicated by the top bounding curve of the orange area, constitute the threshold of feeling. At even higher levels, say 140 dB, the “feeling” becomes quite uncomfortable and we reach the threshold of pain.
The grey area shows the range of frequencies and sound pressure levels used in human speech communication. The blue area shows the range encompassed by music.