Quiet-List 1997

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Measurement/Question/Sensitivity



Dear List:
Measurement:
I believe we are re-inventing a lot of wheels!  The physics of sound
propagation is well understood and good libraries will have copious
material!
European countries have standards and codes of practice for the
prediction of road traffic and airport noise as well as recommendations
for maximum ambient levels in internal environments and for speech
intelligibility.  I would be surprised if the USA and Canada don't have
equivalent codes [even South Africa is well armed with these].
Ideally, noisy equipment should be specified by maximum permissible
sound power level. As this is extremely difficult to measure in the field,
an in-situ maximum permissible sound pressure level has to be specified;
alternatively, a maximum free field sound pressure level at a defined
distance.  For free field hemispherical sound propagation [ie usual short
range circumstances], the sound pressure level derived from a given
source drops by roughly 6dB for every doubling of distance from the
source. [BUT dB's are not a measure of annoyance!]
Question/Sensitivity, etc.:
In terms of sheer weight of damage to human civilisation, I am sure that
noise is among the top 10.  However, I remain convinced that the only
way forward for us anti-noise activists is to quantify noise damage in
terms of hard cash and that means research.  It means hard cash to
move an airport or road and it costs hard facts for the legislators and
courts to take noise seriously, even if part of those hard facts have to be
the realities of aggresive political agitation and lobbying.  Cigarette smoke
is easier to get a grip on than noise and therefore noise will be
correspondingly more difficuflt to overcome.  I expect the processes will
have to be much the same - ie established, repeatable Health/Noise
correlation and un-questionable cost apportionment followed by long and
focused lobbying.
A ray of light at the end of the tunnel seems to be the intention of the
British Government to research the social cost of noise during 1998. 
Hopefully, the end of 1998 will therefore present us with something
meaningful to build on, even if it has emerged from a European context.
Regards ...

John D'Arcy-Evans
tel.:     (021) 400 3860
fax:     (021) 419 7096
E-mail: jdevans@ctcc.gov.za


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