Average thresholds in the 8 to 20 kHz range in young adults.

The sound-pressure level thresholds in the extended high-frequency range (8 to 20 kHz) were measured in 25 non-hearing-impaired young adults from 20 to 29 years of age. The result was not unlike that obtained by previous investigators; the thresholds increased gradually as a function of frequency. However, two notable points were found: one that the threshold reached a plateau above 18 kHz, and the other that it decreased slightly at 12 kHz. As the subjects might respond to the low-frequency noise of the stimulus wave, the threshold became a plateau above 18 kHz. An acoustic resonance in the ear canal caused the threshold to decrease at 12 kHz. In clinical studies of extended high-frequency audiometry, the threshold data should be carefully evaluated above 18 kHz and at 12 kHz.