Hi Rob and David,
unfortunately many people, and technicians too, misuse dB(A), e.g. to
demonstrate that wind turbines produce "acceptable" noise, but not
considering that low frequency pressure changes are not perceived by ears
but are perceived more by the whole body, as for the lowest octaves of a
church organ, producing very annoying effects.
Noise can have an impact on our health, it is demonstrated that noise
affects cardio-vascular diseases. And an increasing number of studies
demonstrates the negative impact of noise on animals.
I think it is now important to declare that a good environmental status is
also based on a good soundscape around us. The buzzing electric lines are
annoying, and I think it is important to say that we don't want to live in
an environment affected by noise everywhere, coming car traffic, airplanes,
electric lines. Whenever possible these sources of noise should be limited
or modified to be quieter. In Italy many power lines are being buried to
preserve beautiful landscapes. I some case we should do the same to
preserve the quietness of beautiful soundscapes where we can enjoy silence
and nature sounds together.
the concept of wilderness, also includes the concept of quietness, intended
as no presence of anthropogeinc noises. In US "wilderness" is an important
concept, if I'm not wrong, this concept was "created" in US with the very
first national parks. Maybe you can use this "concept" to trigger attention
on the problem you mention.
Also, a review of literature about the impact of noise on human health
could help.
Gianni
2014-10-03 2:04 GMT+02:00 [naturerecordists] <
>:
>
>
> > How "loud" is a 65dBA in a natural habitat?
>
> Rob,
>
> Exactly 65dBA. The problem is that "acceptable" levels are set by people
> with no knowledge of sound. For instance a random natural noise of 65dBA,
> or
> a waterfall, or a seashore, could be argued to be acceptable.
>
> However a single frequency noise, or a pulsing noise, or a low frequency
> hum, all at 65dBA, can be exceedingly irritating to human ears. Also we
> have
> little data on how noise affects wildlife.
>
> The A-weighting curve does not give a true indication of how noises affec=
t
> human perception. At 60Hz, the A-weighting curve is at around -27dB,
> meaning
> that the actual sound level is 27dB higher than indicated on a sound leve=
l
> meter, and 65dBA becomes about 92dB - which could be damagingly loud. Thi=
s
> can make nonsense out of A-weighted noise meters.
>
> The effect for us recordists would be worse, as the inverse square law
> only
> applies to a point source, and a transmission line is not a point source
> and
> would carry more at a distance.
>
> What is also not measured is ultrasound, and high voltage transmission
> lines
> give off ultrasound from corona discharges which can get quite noisy when
> damp. This doesn't carry well with distance but it could have an adverse
> effect on wildlife locally. Not only bats but some birds use ultrasound
> detection. A bat detector will show this noise up.
>
> I've also looked into an example of subjective noise disturbance with win=
d
> turbines. I made a submission to a Public Inquiry over induced secondary
> wake noise. This is when turbulence pulses at about one a second meet a
> tree
> or a house, where locally they generate a regular swooshing sound but
> which
> are not measurable in free air with a meter, but which can make a house
> uninhabitable.
>
> David Brinicombe
>
>
>
--
Centro Interdisciplinare di Bioacustica e Ricerche Ambientali
Universit=C3=A0 degli Studi di Pavia
Via Taramelli 24, 27100 Pavia
http://www.unipv.it/cibra
http://mammiferimarini.unipv.it
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
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