ISO 28961:2012 音響学—フリーフィールドリスニング条件下での18歳から25歳までの年齢範囲の耳鼻咽喉科的に正常な人の聴力閾値の統計的分布 | ページ 2

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, 2.

The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 28961 was prepared by Technical Committee ISO/TC 43, Acoustics.

Introduction

The threshold of hearing in a free sound field is specified in ISO 226 and ISO 389-7 . Threshold data in these documents were obtained from otologically normal persons in the age range 18 years to 25 years inclusive.

As described in ISO 389-7, the threshold of hearing varies among people; the documents merely present median values of hearing thresholds. However, other values on the threshold distribution of individuals are necessary to evaluate the hearing ability of a person in relation to that of the population. Those values have been used also in noise evaluation for estimating the ratio of young people with normal hearing in the population who might be able to detect a sound of concern, e.g. an unwanted sound emitted from a machine.

This International Standard provides a method for calculating percentiles of the hearing threshold distribution for one-third-octave-band and other audiometric frequencies from 20 Hz to 16 000 Hz. The mean value of distribution is set to be the threshold of hearing specified in ISO 226 and ISO 389-7. Furthermore, the method has been developed using many of the hearing threshold data on which those documents were based.

1 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.

The percentiles are given in numerical form for the preferred frequencies in the one-third-octave series from 20 Hz to 16 000 Hz inclusive, in accordance with ISO 266, 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.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

Bibliography