scope:

The scope of this standard includes the measurement of the intelligibility of speech over entire communication systems and the evaluation of the contributions of elements of speech communication systems. The scope also includes evaluation of the factors that affect the intelligibility of speech.

In this standard the intelligibility of speech over a speech communication system is measured by comparing the monosyllabic words trained listeners receive and identify with the words trained talkers or speech coders speak into a communication system that connects the talkers (or speech coders) with the listeners. The standard requires the intelligibility measurements to be made with talkers and listeners who are native speakers of English and who have no speech or hearing defects.

Limitations. This standard specifies what should be measured and reported to assess a communication system, but it does not specify the test conditions. This limitation prohibits comparisons between evaluations done under different test conditions.

This standard is not intended for use in evaluating automatic speech recognition devices; the sets of speech materials specified in this standard have not been shown to be appropriate or valid for testing systems that include such devices.

This standard is not intended for use in evaluating the intelligibility of text-to-speech systems; the sets of speech materials specified in this standard have not been shown to be appropriate or valid for testing such systems.

This standard is not intended for use in evaluating the articulatory abilities of talkers with speech disorders or for use in evaluating the speech discrimination abilities of listeners with hearing deficiencies.

This standard is not intended for use in evaluating listeners' abilities to identify talkers or their emotional state. Neither is the standard intended for use in evaluating the overall quality of a speech communication system.

Purpose

The purpose of this standard is to establish uniform methods for measuring the intelligibility of speech over communication systems. The measurement process involves talkers, in their environment, who speak test words into a transmission path to listeners, who receive and identify the speech in their environment. Figure 1 shows a simple block diagram of such a measurement system.

This standard is intended to be particularly useful to the following groups:

− Preparers of specifications for the performance of speech communication systems, equipment, and facilities;

− Architects and consulting engineers who design spaces and equipment for speech communication;

− Developers, designers, and manufacturers who wish to describe the performance of speech communication equipment; and

− Evaluators of the performance of different talkers, environments, transmission paths (including communication equipment), listeners, or usage procedures for speech communication systems.

Others who may find portions of the standard helpful include users of speech communication systems, people who select and train such users, designers, or selectors of the environments in which the systems and equipment will be used, and people who wish to adopt or to modify parts of the standard to suit purposes which are outside its scope.

Applications

The standard is intended for use in measuring the intelligibility of English speech in either indoor or outdoor spaces over a communication system. Examples of the spaces are offices, vehicles, enclosures, auditoriums, and amphitheaters. In large spaces, where intelligibility is not uniform across the space, multiple measurements or a single measurement in a "typical" location should be made. Examples of the equipment are public address systems, telephones, intercommunication systems, radiotelephones, underwater telephones, broadcast systems, and special systems for speech communication. The standard also is intended for use in evaluating the contribution of the individual components of the communication systems, such as microphones, loudspeakers, headsets, and electronic equipment-and the contribution of the methods of using the components-to the intelligibility of speech over the communication systems.