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Audio Contrast

From: David MacDonald <befree@magma.ca>
Date: Tue, 2 Nov 2004 18:36:20 -0500
Message-Id: <200411022336.iA2NaLfx023128@mail1.magma.ca>
To: <w3c-wai-gl@w3.org>
Today I had a conversation with Dan Paccioretti of the Provincial Resources
program for Cochlear Implants and Auditory Training Equipment (PRP-CI & AT)

He is also on the Board of the Canadian Sensory Institute.  He is an
Audiologist. I had him review my audio examples for his opinion if I
accurately captured a "good" and "bad" example of "Audio Contrast". He liked
the examples and said they accurately demonstrated what we were trying to
get across and that the 20db difference in the good and bad example sounded
accurate. He says they are keepers. He also confirmed with all our other
sources that say 20db's represents about a 4x increase in perceived volume.
He says this is quite well known and accepted among people in the field.


Dan also agreed with Wendy's post from last year where the people at Shure
recommended a *minimum* of 20 db and that 30db's is even better.




Dan added that the greater the signal to noise ratio the better. Based on
that and the Shure post, I will submit a recommendation to Guideline 1.4
that adds a line to say that greater contrast improves comprehension for
many people with hearing loss. So I retract my initial recommendations that
we reduce the 20 db contrast to pacify the movie and commercial industry.
Forgive me, I love loud music. :-)


In the audiology business, they don't generally use the term "audio
contrast" but rather "signal to noise" ratio. In my days as a producer, I
thought of signal to noise in different terms.(i.e., tape hiss or white/pink
noise) We didn't think of background music being "noise" although many
musicians only played noise. <jk>


Having said that, perhaps we should include the correct term "signal to
noise" in our guidelines to honour audiologists and people in that field who
may be reading our guidelines. 


Dan also made an interesting observation when I asked him if there are any
other aspects of the web that we should address from a hearing perspective.
He said that our guidelines on visual contrast, and guidelines that make the
web more visually accessible will help people with hearing loss also because
they rely so actively on their visual perception. And clarity is key, both
visually and auditorily.



David MacDonald


Access empowers people...
         .Barriers disable them.



Received on Tuesday, 2 November 2004 23:36:26 UTC

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