BS ISO 28961:2012

Foreword
Introduction
1 Scope
2 Normative references
3 Calculation of percentiles of hearing threshold
  distribution
Annex A (informative) - Numerical examples
        to illustrate the procedure
Annex B (informative) - Selected values of
        the statistical distribution of hearing
        thresholds of otologically normal persons
        in the age range 18 years to 25 years inclusive
Annex C (informative) - Selected values of Z[x]
Annex D (informative) - Notes on the derivation
        of the statistical distribution of
        normal hearing thresholds
Bibliography

Gives descriptive statistics, percentiles, of the hearing threshold distribution whose mean is the reference threshold value specified in ISO 226 and ISO 389-7.

This International Standard provides descriptive statistics, percentiles, of the hearing threshold distribution whose mean is the reference threshold value specified in ISO226 and ISO389-7. The mean and percentile thresholds are specified under the following conditions: the sound field in the absence of the listener consists of a free progressive plane wave (free field); the sound source is directly in front of the listener (frontal incidence); the sound signals are pure (sinusoidal) tones; 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; listening is binaural; the listeners are otologically normal persons within the age range 18years to 25years inclusive. NOTE1 The xth percentile threshold is the value of threshold below which x%of the individual thresholds of population fall. The threshold distributions in this International Standard have been derived from the results of comprehensive statistical analyses. See AnnexD. NOTE2 The applicability of the percentiles and the values of parameters given in this International Standard to diffuse-field listening conditions has not been examined. They are expected to be applicable to the conditions for the frequencies from 20Hz to 250Hz where the threshold difference between free-field and diffuse-field listening conditions is zero as specified in ISO389-7:2005, Table1. The percentiles are given in numerical form for the preferred frequencies in the one-third-octave series from 20Hz to 16000Hz inclusive, in accordance with ISO266, and for some intermediate audiometric frequencies. The percentiles are applicable to the assessment of an individual\'s hearing in relation to the distribution of hearing thresholds under the above conditions. The percentiles can also be used to evaluate the audibility of low-level noise around hearing threshold. NOTE3 An application example of hearing threshold distribution to noise evaluation can be found in ISO7779:2010, AnnexD.