IEC 60268 16 PDF

IEC Sound system equipment – Part Objective rating of speech intelligibility by speech transmission index. according to the standard IEC (edition 4). STI and. STIPA are the most established methods for measuring speech intelligibility. Speech Transmission Index (STI) is a measure of speech transmission quality. The absolute RASTI was standardized internationally in , in IEC . Since then, IEC was revised three times, the latest revisions (rev.4).

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STI measuring instruments are and have been made by various manufacturers. The Modulation Transfer Function MTF describes to what extent the modulation m is transferred from source to receiver, as lec function of the modulation frequency F, which ranges from 0.

The electrical output always operates at the same level. Objective rating of speech intelligibility by speech transmission index Status: Do you need a multi-user copy?

Although Schroeder 2 has shown that the MTF can also be calculated from the impulse response, handheld STIPA meters use modulated noise as a test signal, whereas most PC based simulation and measurement software uses the impulse response method.

Acoustics Engineering – Speech Intelligibility

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Manfred Schroeder writes an article in Acustica in which he showed that the modulation transfer function MTF can be derived from an impulse response. Subsequent revisions of the standard have added i.

Modulated noise versus impulse responses The work of Houtgast and Steeneken is based on a STI method using modulated noise as a test signal. With Dirac 6 you only need a single system- and level-calibrated measurement per position. Also, because in sweeps all the energy is always concentrated at a single frequency, it is more difficult for amplifiers and speakers to handle this type of signal.


In very large spaces such as cathedralswhere echoes are likely to occur, the indirect method is usually preferred over direct method e. Since then, IEC was revised three times, the latest revisions rev. Search all products by. The IEC ed4 Standard defines a qualification scale in order to provide flexibility for different applications. This page was last edited on 27 Mayat The Echo speech source can now be used for this purpose as explained in this blog post.

This signal is available at 60 dB A and at a raised level of 72 dB A. Also, depending on the type of impulse response measurement that is used, the influence of background noise present during measurements may not be dealt with correctly. An IEC maintenance team is currently working on rev. Definition and Measurement,’ Acustica 49, – Hence, the MTF depends on the system properties and the background noise.

This fourth edition cancels and replaces the third edition, published inand constitutes a technical revision. With the introduction of Dirac 6 and the Echo Speech Sourcespeech intelligibility measurements can be performed very quickly and easily.

The STI measures some physical characteristics of a transmission channel a room, electro-acoustic equipment, telephone line, etc. Dirac however has 60628 able to handle asynchronous MLS signals since version 4. The following test report forms are related: The influence [1] that a transmission channel has on speech intelligibility is dependent on:. Your basket is empty.

Speech transmission index

At this time, this simplified STI derivative was still stipulated as a standard method in some industries. By using this site, you agree to the Terms of Use and Privacy Policy.


STI predicts the likelihood of syllables, words and sentences being comprehended. This means that the indirect method should only be used iex great care when measuring Public Address systems and Voice Evacuation systems. Traditional modulated noise based speech intelligibility measurements contain a limited number of modulation frequencies. The STI isc based on the relation between perceived speech intelligibility and the intensity modulations in the talker’s voice, as described by Houtgast, Steeneken and Plomp.

Articles with hAudio microformats. Audio equipment, Acoustic measurement, Audibility, Ratings, Performance testing, Public-address systems, Signal-to-noise ratio, Audio systems, Communication equipment, Speech recognition, Speech transmission systems, Acoustic testing, Acoustic properties and phenomena, Telecommunication systems, Grades quality.

Speech Intelligibility

Note that the MLS sequences are coded such that Dirac can always determine the output level, and correct the STI calculations appropriately. We accept all major credit cards American Express, Mastercard and VisaPayPal and bank transfers as form of payment. You may find similar items within these categories by selecting from the choices below:. With the standard impulse response technique it is difficult to measure a high quality impulse response and at the same time retrieve an accurate background noise level from this measurement.

Intermittent stimulus New in Dirac 6 and also used in the Echo is the intermittent stimulus.