Just to expand on Bernard's advice, maybe they could first try feeding the
output from the TV into an audio amplifier with a graphic equalizer; turning
down all frequencies outside normal speech (beyond 500Hz and above 2Khz or
so) and then experimenting with the remaining controls to try to filter out
unwanted sounds? It's worth trying before starting to use digital editing
techniques on the soundtrack, especially if it's a scratchy old VHS they're
still using. The technicians in the library or AV labs have probably got
some really good quality amps sitting around they can finally justify
spending all that money on. Some amps even have the ability for any sounds
below a certain volume level to be masked out, which might help.
Obviously, the student should be allowed to try out headphones. If the
student uses hearing aid(s) with T position setting, maybe using radio
microphone kit to link directly to the output of the TV or audio amp could
allow him/her to make better use of any sound cancelling/enhancing features
of the hearing aid (e.g. RNID sell the Conversor kit with optional SCART
adapter).
I doubt attempts to improve the quality of the speech element of the
recording will affect the validity of the test. I suspect the task involves
understanding native language speakers, rather than a test of hearing range
and ability on busy streets in Paris, unless perhaps it's a course in being
a French Traffic Warden ...
The department might need to arrange an alternative to this test. Providing
a transcript probably defeats the object completely. Re-recording the
dialogue might not be effective, as the student might normally use
lip-reading skills (possibly without realising, as many people do) to
support hearing, so you'd have to be sure the new recording is precisely
synchronised to the video. I guess it's time for the tutors to start to
evaluate new AV materials to use on the course that have better quality
audio recordings.
Just to clarify: EQ isn't normally used to remove vocal tracks from music.
This is done by inverting the phase of the left or right audio track
(assuming a stereo recording). The idea is that anything in the centre of
the mix (usually the vocals) will be cancelled by two equal but inverted
waves playing at the same time. It doesn't work, but it does sometimes sound
like they made the vocalist sing into a bucket in the hall outside the
studio.
Ian
----- Original Message -----
From: "A Velarde" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, February 23, 2008 9:40 AM
Subject: Re: reducing background noise on videos
So Bernard. It is possible but may be not be the entire solution as some
noises could not be ammelliorated or eliminated completely, right? Andy
----- Original Message -----
From: BERNARD DOHERTY
To: [log in to unmask]
Sent: Friday, February 22, 2008 5:35 PM
Subject: Re: reducing background noise on videos
Um, I don't think things work quite this way. What happens is some
frequencies can be boosted and others lowered. Various bits of software
that promise to take out vocals from CDs so that you can sing along work
this way: they just take out the centre of the recording, including all the
instruments there. With a digital recording of the video, the sound track
could be passed through an equaliser and the top and bottom noise reduced to
emphasise the vocal, but any other noise at the same frequency will also be
boosted.
A better question is what is achieved if the vocal is isolated? If an
uncluttered vocalisation is all that is wanted, have a native speaker read a
transcript. If that is not acceptable for some reason, then what is being
tested should be more clearly identified. It is important to ensure that it
is a form of testing that a deaf or hearing impaired person could pass.
Regards, Bernard
Bernard Doherty
Assessor
Cambridge Access Centre
A Velarde <[log in to unmask]> wrote:
Just a thought. Maybe someone with some iT expertise could confirm
this. Software that is used to produce music could isolate different type
of noises ( melodies form different instruments), would such software be
used to eliminate or ameliorate the background noises digitally? Andy
----- Original Message -----
From: Barbara Denton
To: [log in to unmask]
Sent: Friday, February 22, 2008 1:16 PM
Subject: reducing background noise on videos
We have a student doing a language course, which involves listening to
a video and writing answers to questions in response. Most of the videos
have noisy settings e.g. people being interviewed on a Paris street with
traffic roaring by. The student, who has a hearing impairment, can't hear
these either in the practice labs (where there is the problem of not
disturbing other students), or in the assessments (where they can be on
their own) because of the excessive background noise. The School have
consulted RNID and tried various solutions, but haven't come up with
anything that works yet.
Any ideas?
Thanks
Barbara Denton
IT Disability Support Officer
Birkbeck College
020 7079 0717
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