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Re: Music Transmission Index?

Dear List,
The Speech Transmission Index (STI) is a measure of Speech Intelligibility.
Speech Intelligibility, being concerned with information content, is not at
all the same thing as Speech Quality, and the two things do not have to
correlate with each other at all. (It is possible to manipulate speech
signals and create signals which maintain very high levels of
intelligibility but score extremely low on all the Audio Quality measures.)

When someone coins a new term, Music Transmission Index, I assume they
choose the wording carefully. Thus I wonder whether they mean something
analagous to STI but in the music domain, rather than something like PESQ or

It is not far-fetched to consider the concept of Information Transmission
with respect to music signals. This applies to the 'passive' listener, who
obviously wants to be able to hear what is happening in the music (witness
the well-known relationships between optimal reverberation and musical
genre), but applies even more to the performers of the music, who are
engaged in intense communication with each other via the signals they

I carried out studies about 15 years ago which had a certain degree of
success in applying STI-like principles to the case of musical communication
between performers. I was foolish enough to publish the results in (the old)
Acustica at about the same time as that journal's circulation approached
zero, so nobody has read them.
References, in case anyone is interested:
Naylor GM and RJM Craik, "The Effects of Level Difference and Musical
Texture on Ease of Ensemble." Acustica 65, pp95-100, 1988.
Naylor GM, "Modulation Transfer and Ensemble Music Performance." Acustica
65, pp127-137, 1988.
Naylor GM, "Some Effects of Signal and Noise Modulation on Rhythm Detection,
and Relations to Musical Performance in Rooms." Acustica 73, pp208-214,
Naylor GM, "A Laboratory Study of Interactions Between Reverberation, Tempo
and Musical Synchronization" Acustica 75, pp256-267, 1992.

Graham Naylor
Oticon Research Centre

-----Original Message-----
From: William C. Treurniet [mailto:wtreurniet@xxxxxxxxxx]
Sent: 11 January 2005 20:55
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Re: Music Transmission Index?

In 1998 and 2001, the International Telecommunications Union (ITU) published
a recommendation for the objective quality measurement of music,
particularly music that has been degraded somewhat by lossy compression
algorithms such as mp3. The measurement method, called PEAQ for "Perceptual
Evaluation of Audio Quality", compares physical attributes of a processed
audio signal with the original signal. The method was calibrated using data
from a number of human listening experiments conducted in several
laboratories. Generalization tests using data from new experiments gave
correlations well over .8 between the PEAQ measure and average subjective
quality ratings. Correlations between simple SNR and average subjective
quality ratings were always much lower.

The PEAQ quality measure might be considered a "Music Transmission Index".

Links to information about PEAQ may be found at


William Treurniet