scope:

This International Standard provides descriptive statistics, percentiles, of the hearing threshold distribution whose mean is the reference threshold value specified in ISO 226 and ISO 389-7. The mean and percentile thresholds are specified under the following conditions: a) the sound field in the absence of the listener consists of a free progressive plane wave (free field); b) the sound source is directly in front of the listener (frontal incidence); c) the sound signals are pure (sinusoidal) tones; d) the sound pressure level is measured in the absence of the listener at the position where the centre of the listener's head would be; e) listening is binaural; f) the listeners are otologically normal persons within the age range 18 years to 25 years inclusive.