refers to the level of a pure tone of a given frequency that is minimally detectable by a person with normal hearing. For example, the for a 1-kHz pure tone is 7.5 dB SPl. (sound-pressure level) for TDH49 headphones, according to U.S. standards (ANSI S3.6- 1996 Specification for Audiometers). Audiometric zero is used to calibrate audiometers and therefore, by definition, represents 0 dB HI. (hearing level). See also audiogram.
AUDIOMETRIC ZERO: “An audiometric zero represents 0 dB HI or no sound.”