The audible frequency is from 20K t0 20,000K according to audio magazines, but in reality, a persons ability to hear falls off rapidly after 16,000K. This can easily be verified by amplified test tones on a loudspeaker.@orpheus10 it should be 20 Hz to 20,000 Hz, the latter is sometimes written as 20 kHz.
You are totally correct that for most of us the hearing drops off earlier than 20 kHz.