The audible frequency range of a human ear is

The audible frequency range of a normal human ear is generally defined as 20 Hz to 20,000 Hz (20 kHz) [t1][t4]. Frequencies below 20 Hz are classified as infrasound, which are typically beyond human perception, while frequencies above 20,000 Hz are known as ultrasound [t1]. While the absolute borders are 20 Hz to 20,000 Hz, human hearing is most sensitive in the 2,000 to 5,000 Hz range, which is critical for understanding speech [t2][t7]. Factors such as age, gender, and noise exposure can reduce this range; for instance, many adults lose sensitivity to higher frequencies, often seeing their upper limit drop to between 12,000 Hz and 17,000 Hz [t3][t5][t8]. However, the standard nominal range used in scientific and medical contexts remains 20 Hz to 20,000 Hz [t6].

Sources

1. [1] https://en.wikipedia.org/wiki/Hearing_range
2. [2] https://www.ncbi.nlm.nih.gov/books/NBK10924/