1410 Chapter 36
to rapidly expand. As DSP technology continues to
grow and as our understanding of psychoacoustics and
speech continues to develop, the ability to manipulate
speech signals to provide greater intelligibility will
increase. Measuring such processes will be a further and
interesting challenge.
Particular areas that are likely to see progress over
the next few years are the development and use of bin-
aural intelligibility measurements—probably using STI
as their basis. The author has also tried using STI and
STIPA to assess speech privacy and the effectiveness of
speech masking systems. While potentially a promising
technique, there are still many obstacles to overcome
before it can become a viable technique—not least of
which requires considerable research to be carried out
between speech intelligibility and STI at the lower end
of the STI scale (Mapp 2007). The measurement and
intelligibility assessment of assistive hearing systems is
also currently under investigation (Mapp 2008) and is
showing considerable promise. It is anticipated that a
series of new criteria and measurement techniques will
be developed specifically for this specialized but
increasingly important field. The use of real speech and
other conventional PA signals is also under research and
should pave the way for less invasive measurement
techniques.Acknowledgments
The author gratefully acknowledges the assistance of JBL Professional for allowing a number of graphs and figures
originally created for their Technical Note “Speech Intelligibility” (TN, vol. 1, no. 26) to be reproduced in this chap-
ter. The author would also like to thank Don and Carolyn Davis for holding the first Syn-Aud-Con Speech Intelligibil-
ity Workshop in 1986, which has acted as an inspiration to further work on this subject ever since.
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