BS ISO 9921-1:1996- Ergonomic assessment of speech communication -
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This part of IS0 9921 provides a method for prediction of the effectiveness of speech communication in the
presence of noise generated by machinery (lSO/TR 12100-2) as well as in any other noisy environment. It describes a method for the assessment of direct speech communication with respect to the following parameters:
- ambient noise at the speaker’s position;
- ambient noise at the listener’s position;
- vocal effort;
- distance between the communication partners.
The physical and personal conditions assumed for this
part of IS0 9921 are:
a) Physical conditions:
- reverberation time less than 2 s at 500 Hz;
- direction of speech towards the listener;
- the listener’s line of sight arbitrary;
- lip reading not assumed;
- electroacoustic transmission systems excluded;
- no acoustic barrier between speaker and listener.
b) Personal conditions:
- binaural listening;
normal hearing capacity in accordance with
IS0 7029, i.e. medium hearing threshold
levels for males up to 70 years of age not
exposed to harmful noises (see annex A);
- hearing protectors worn by the speaker;
- neglected influence of hearing protectors
worn by the listener (a method which takes
into account the wearing of hearing protectors by the listener will be addressed in the
future part 2 of IS0 9921);
- speakers and listeners both familiar with the
language used and the speech message;
- clear articulation (see lSO/TR 4870);
- speech message consisting of monosyllabic
words to represent the worst case.
