IEC 60268-16:2020 

Sound system equipment - Part 16: Objective rating of speech intelligibility by speech transmission index


Do you need a multi-user copy?




IEC 60268-16:2020 defines the STI model, test signals, measurement and prediction methods.
The objective of this document is to provide a comprehensive manual for all types of users of the STI model in the fields of audio, communications and acoustics.
This document does not provide STI criteria for certification of transmission channels (e.g. criteria for a voice-alarm system), but some typical application values are provided in Annex G.
Every measurement method has limitations, and the reader is referred to clauses relating to limitations such as speech privacy, echo and systems using digital voice compression (vocoders).
This document does not cover the case of fluctuating noise on the STI, although some general comments on dealing with this complex issue are provided in 7.13 and 8.9.3.
IEC 60268-16:2020 cancels and replaces the fourth edition published in 2011. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) the spectrum of the male speech test signal has been changed, with significant reductions in the 125 Hz and 250 Hz bands being implemented;
b) some corrections to formulae have been made;
c) additional information has been included on prediction and measurement procedures;
d) spectrum and weighting factors for female speech have been removed;
e) verification information for STI measurement devices added;
f) the relationships between STI and number of other speech intelligibility measures have been updated in Annex E;
g) greater information is given in Annex M about adjustments to the measured STI results to simulate effects of alternative ambient noise and speech levels.

Look inside

Additional information

Publication typeInternational Standard
Publication date2020-09-25
Available language(s)English/French
TC/SCTC 100 - Audio, video and multimedia systems and equipmentrss
ICS33.160.01 - Audio, video and audiovisual systems in general
Stability date  2022
File size7022 KB

The following test report forms are related:

Share your publications

Learn how to share your publications with your colleagues, using networking options.

Payment information

Our prices are in Swiss francs (CHF). We accept all major credit cards (American Express, Mastercard and Visa, JCB and CUP), PayPal and bank transfers as form of payment.

Keep in touch

Keep up to date with new publication releases and announcements with our free IEC Just Published email newsletter.

Contact customer services

Please send your enquiry by email or call us on +41 22 919 02 11 between 09:00 – 17:00 CET Monday to Friday.