Which frequency is NOT normally used in calculating pure tone average?

The pure tone average (PTA) is calculated using the thresholds at specific frequencies to determine an individual's overall hearing ability. Typically, the frequencies used in PTA calculations are 500 Hz, 1000 Hz, and 2000 Hz, as these represent important regions of human speech frequencies and are significantly correlated to speech perception.

The frequency of 4000 Hz, while it is an important frequency in audiometric testing, is not included in the standard calculation of the pure tone average. This is because the PTA is intended to reflect the mid-frequency hearing capabilities that are most relevant for understanding speech sounds and is focused primarily on the lower frequencies where most speech intelligibility occurs. Thus, omitting 4000 Hz, a higher frequency, from the PTA calculation makes this option the correct answer.