[LAU] Music for the deaf

[Simon Fielding]

On Tue, 2010-01-19 at 22:57 +0100, Giso Grimm wrote:
> Simon Fielding wrote:
> > My sister is a specialist teacher for hearing-impaired primary school
> > children. As part of her curriculum she includes music and in
> > particular, nursery rhymes etc for the younger children. She would like
> > them to be able to sing these at home with and/or for their parents. For
> > those children with non-hearing-impaired parents, this is not a problem
> > but many of the children also have hearing-impaired parents. Therefore
> > she would like to produce a CD of her singing for the children to take
> > home and use. I would really appreciate any help members can give me as
> > I am not a professional musician or recording engineer.
> > 
> > 1) She will be singing unaccompanied (she is a trained singer and is
> > perfectly competent to do this) in an alto register to avoid any
> > distraction for the children from accompaniments etc. Does anyone have
> > any suggestions about this? (eg effects for recording, effects for the
> > headphone mix etc)
> 
> For most hearing impaired listeners, less reverberation is usually
> better (if understanding the words is desirable). The effect of
> compression very much depends on the accompaniment and/or distracting
> noises; in a clean situation compression usually makes things worse (see
> e.g., R. Plomp: The negative effect of amplitude compression in
> multichannel hearing aids in the light of the modulation-transfer
> function. J. Acoust. Soc. Am., vol 83(6), 1988). Try to avoid pops
> during recording.
> 
> > 
> > 2) This one's a bit more specialist so you may not be able to help -
> > hearing impairment often starts with loss of high frequency response.
> > The obvious thing would seem to be to boost these but I don't know if
> > that would be correct. Does anyone know?
> 
> If they will listen via loudspeaker and wear their hearing aids
> (assuming that they have one), all individualized frequency shaping is
> already done by the hearing aid. Listening via headphone is not really
> working with hearing aids, thus an individual frequency shaping might be
> beneficial. However, for that you need to know a bit about the
> individual hearing (e.g., hearing threshold and whether it is
> sensorineural or conductive loss, as a bare minimum). A very simple rule
> of thumb is to apply a frequency dependent gain which is 40% of hearing
> threshold for sensorineural loss and 100% of threshold for conductive loss.
> 
> Linux audio tools can be used to do batched pre-filtering of audio
> material based on individual hearing loss (e.g., the command line tool
> 'applyplugin' which applies LADSPA-Plugins to files, can load equalizers
> and set their gains).
> 
> Best regards,
> 
> Giso
> 
> 
> > 
> > Any comments on any other aspects of this project would also be more
> > than welcome.
> > 
> > Hopeful regards,
> > Simon
> > _______________________________________________
> > Linux-audio-user mailing list
> > Linux-audio-user at lists.linuxaudio.org
> > http://lists.linuxaudio.org/listinfo/linux-audio-user

Thank you for your comments. Unfortunately, I don't have enough
knowledge of the field to assess the relative merits of Plomp (1988) v
Villchur's response :-

Villchur, E. (1989) “Comments on ‘The negative effect of amplitude
compression in multichannel hearing aids in the light of the
modulation-transfer function,’” Journal of the Acoustical Society of
America, 86, 425-427 [Letter]

However, both of these (and other related research) seem to relate to
the design and implementation of hearing aid technologies. Therefore,
your point seems to me to be still valid. One would assume that the
children would have appropriately selected hearing aids and that any
compression, expansion and frequency boosting is best done by the
hearing aids. The implication of this is that the recording should be as
clean as possible with little or no effects or EQ applied. The singer
should try to maintain uniform dynamics in the performance rather than
have this done by compression or other plugins in the mixing/mastering
stages. All of this seems logical and reasonable to me and in some ways
rather simplifies the task, assuming that the singer can create an
appropriate performance (which I believe to be the case).

As regards individual tailoring of the recordings, this is currently a
little beyond the scope of what we are doing although your suggestions
are interesting and I may suggest this as an area for further
investigation to my sister if she feels able to do it and can find
suitable subjects to assist in any investigation.

Having seen the information provided by many members on this list, it
should not be the case but I continue to be surprised by the breadth and
depth of knowledge shown here. Thank you to all who have commented on my
(possibly unusual) request for information and thanks in advance to any
who may add more.

Regards,
Simon