-------- Original Message --------
Subject: Re: skating rink music, and hearing loss correction
Date: Mon, 27 Sep 1999 23:50:12 +1000
From: Bob Douglas 
Reply-To: rdouglas@mail.usyd.edu.au
Organization: Sydney Conservatorium
To: Laszlo Vecsey 
References: 


Laszlo Vecsey wrote:
> 
> You know how in skating rinks theres usually a huge amount of reverb or
> echo because of the properties of the large room and reflective ice? I was
> wondering if anyone could suggest a process to 'dull' or 'depmhasize' the
> sound so that when played back in a large room like that, it would sound
> better.

Dufay wrote a piece specifically to be performed in Brunellesci's dome
where the  tempo of the music was such that a reverberating phrase
returning from the walls of that space formed a canon with the next
phrase being sung. That was half a millennium ago, so it should not be
impossible in principle today to broadcast waveforms which are inverted
copies. The rate of switching between the original and its cancelling
inversion becomes a tuneable parameter of the particular space in
question - ie. along the lines of the method currently employed to cloak
the noise of submarine propellors.

> Also, I believe I have a slight hearing loss in part of my hearing (the
> speaking range) -- I have a fairly high end headphone setup and amplifier,
> same goes for my sound card, and I was thinking of wirting a program that
> would play some tones at low volume (just above the threshold of hearing
> for that particular user, done through a midi input device for example to
> help) so that a fairly accurate frequency map could be established that
> would take into consideration that particular set up of headphones/amps
> and listening ears. Then, a realtime csound process could manipulate audio
> coming from line-in and correct it properly -- in my case, I could then
> play on my digital piano and have my fingers become used to the so called
> 'average' set of ears out there, in effect everything coming through
> line-in could be adjusted to the appropriate levels for my listening.
> 
> I'm still at a loss as to whether that minimum tone would be enough to
> base any frequency shifts on, perhaps the loud end of the spectrum needs
> to come into play and then more averages need to be taken.. sorry if this
> isn't too clear, I hope I've managed to present the idea.

If I understand you correctly, you are suggesting a means of
compensating for hearing loss by boosting those frequencies which define
the loss region. I believe this does not take into account the fact that
we all have our own audiologically unique response to the aural
environment - no two basilar membranes behave the same (even in each of
two ears mounted on the same head!). 
In short, our own individual way of hearing is moulded as much by those
spectral regions where we experience an attenuation of aural
sensitivity, as it is by those where we possess an increased perception.
There is no such thing as a "monotonic" ear, let alone a linear one.