An audio frequency or audible frequency is characterized as a periodic vibration whose frequency is audible to the average human. It is the property of sound that most determines pitch and is measured in hertz (Hz).
Hence, the range of frequency within which the sound can be heard by a human being is called the audible range of frequency.
The human auditory system is sensitive to frequencies from about 20 Hz to a maximum of around 20,000 Hz, although the upper hearing limit decreases with age. Within this range, the human ear is most sensitive between 2000 and 5000 Hz, largely due to the resonance of the ear canal and the transfer function of the ossicles of the middle ear. The high sensitivity region at 2000 - 5000 Hz is very important for the understanding of speech.