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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Your basket is empty. STI is a well-established objective measurement predictor of how the characteristics of the transmission channel affect speech intelligibility. An IEC maintenance team is currently working on rev. Subsequent revisions of the standard have added i. The new intermittent stimulus consists of an MLS sequence followed by an equally long period of silence. TNO did produce and sell instruments for measuring full STI and various other STI derivatives, but these devices were relatively expensive, large and heavy.

Accept and continue Learn more about the cookies we use and how to change your settings. You may experience issues viewing this site in Internet Explorer 9, 10 or Another important factor determining the speech intelligibility is the background noise level.

Plots of the STI versus the source-receiver distance can be created with a few mouse clicks. This website is best viewed with browser version of up to Microsoft Internet Explorer 8 or Firefox 3. Hence, the MTF depends on the system properties and the background noise.

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Speech transmission index

The IEC ed4 Standard defines a qualification scale in order to provide flexibility for different applications. However, the requirement that the channel must be linear implies that the indirect method cannot be used reliably in many real-life applications: Another method is defined for computing a physical measure that is highly correlated with the intelligibility of speech as evaluated by speech perception tests given a group of eic and listeners.

This means that the indirect method should only be used with great care when measuring Public Address systems and Voice Evacuation systems. The STI is based on the relation between perceived speech intelligibility and the intensity modulations in the talker’s voice, as described by Houtgast, Steeneken and Plomp.


Search all products by. 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 transmission index – Wikipedia

Problems playing this file? By using this site, you agree to the Terms of Ice and Privacy Policy. RASTI was designed to be much faster than the original “full” STI, taking less than 30 seconds instead of 15 minutes for a measuring point.

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.

A continuously decreasing MTF indicates the influence of reverberation and an MTF that decreases first and then increases again indicates the presence of an echo. The list does not include software producers that produce STI-capable acoustic measuring and simulation software. Impulse responses contain the full spectrum of modulation frequencies, and Dirac 6 now has the ability to show them in continuous MTF graphs.

Retrieved from ” https: It is therefore no longer necessary to work with external equalizers or 6026 set the output level.

Communication Hearing Human voice Sound Waves.

BS EN 60268-16:2011

From Wikipedia, the free encyclopedia. Dirac however has been able to handle asynchronous MLS signals since version 4. Definition and Measurement,’ Acustica 49, – You may find similar items within these categories by selecting from the choices below:.

It is described as the preferred parameter for almost all measurement ifc. A new function for the prediction of auditory masking effects is introduced; – the concept of ‘speech level’ and the setting of the level of the test signal have been introduced; – additional information has been included on prediction and measurement procedures.

A Vol 21 Part 5. The main benefit of the indirect method over the direct method based on modulated test signals is that the full MTF matrix is measured, covering all relevant modulation frequencies in 1 octave bands.


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. Further the following standards have, as part of the requirements to be fulfilled, integrated testing the STI and uec of a minimal speech transmission index:.

STI has gained international acceptance as the quantifier of channel influence on speech intelligibility. Reductions in the modulation depth are associated with loss of intelligibility. The market for STI measuring solution is still developing, so the above list is subject to change as manufacturers enter or leave the market. Download You can download our speech intelligibility technical note as a pdf. With the introduction of Dirac 6 and the Echo Speech Sourcespeech intelligibility measurements can be performed very quickly and easily.

The intelligibility of speech depends in part on the acoustical properties of the enclosure in which the speech is transmitted from speaker to listener. Each revision included updates of the STI methodology that had become accepted in the STI research community over time, such as the inclusion of redundancy between adjacent octave bands rev.

This is because movement of the handheld device during a measurement would make impulse response measurements unsuitable. STI measuring instruments are and have been made by various manufacturers. This page was last edited on 27 Mayat This stimulus allows you to increase the output level and perform 6026 to improve the INR of the impulse response in speech intelligibility measurements, while still retaining accurate noise values.

Click to learn more. The absolute measurement of speech intelligibility is a complex science. Vol 17, part 7. Intermittent stimulus New in Dirac 6 and also used in the Echo is the intermittent stimulus.