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Re: Amplitude and frequency attenuation vs. distance

Subject: Re: Amplitude and frequency attenuation vs. distance
From: "Jim Morgan" fundador_four
Date: Mon May 23, 2011 2:24 pm ((PDT))
Hi John,

I have never attempted to actually calculate any effects that surroundings
have on sound and frequency amplitude. This can become very complicated as
there are so many factors that affect the sounds we hear and record and any
calculations would probably would have, for me anyway, very limited value.

As a nature recorder I try for fairly close sounds with minimal distracting
noise. Of course these conditions are hard to find and I usually end up wit=
h
some sort of compromise.

The test I made http://soundcloud.com/fundador/bell-test-15-30-60-90-150-30=
0
was to satisfy my curiosity as to how much amplitude and frequency are
affected by distance under somewhat controlled conditions. As you can tell
from the recording the effect is very noticeable.

This has turned into a interesting discussion and I also want to thank
Raimund for the information he provided which illustrates the enormous
complexity of this subject.

Jim



On Mon, May 23, 2011 at 10:33 AM, hartogj <> wrote:

>
>
> Hi Jim,
> We are often reminded that sound attenuation with distance approximates a
> reduction of 6dB for each doubling of distance. However, as you and Klas
> point out, the actual attenuation over distance is highly frequency
> dependent. This suggests the 6db rule would only be accurate at one speci=
fic
> frequency, and any general rule would need to include an approximate
> adjustment for frequency.
> Does that make any sense,if so do you know of a common use equation that
> includes a frequency adjustment?
>
> John Hartog
> www.rockscallop.org
>
>
> --- In  Jim Morgan <> wrote:
> >
> > Thank you Klas for the additional information. Your paper provides much
> more
> > detailed information and many members would benefit by reading it.
> >
> > Jim
> >
> > On Sun, May 22, 2011 at 3:42 PM, Klas Strandberg <> wrote:
> >
> > >
> > >
> > > Thanks Jim!
> > >
> > > Let me contribute. This was written in... 1991?
> > >
> > > http://www.telinga.com/attach.htm
> > >
> > > Klas
> > >
> > >
> > > At 21:20 2011-05-22, you wrote:
> > > >As most of us know sound amplitude and frequency are attenuated as t=
he
> > > >distance to the sound source increases.
> > > >
> > > >
> > > >This effect heard from recordings made of various sounds at differen=
t
> > > >distances are often noticeable but difficult to clearly hear.
> > > >
> > > >
> > > >Also recordings made with parabolas amplify the higher frequencies
> more
> > > than
> > > >the low frequencies thereby making the recorded sound seem closer th=
an
> it
> > > >actually is.
> > > >
> > > >
> > > >The following test of sound vs. distance is an example of sound
> amplitude
> > > >and frequency attenuation.
> > > >
> > > >
> > > >Here is a description of the test which is the recorded sound of a
> kitchen
> > > >timer bell at 15, 30, 60, 90, 150, 300 feet. Note the significant
> > > >attenuation of the higher frequencies that increase with distance.
> > > >
> > > >
> > > >Recording at:
> > > http://soundcloud.com/fundador/bell-test-15-30-60-90-150-300
> > > >
> > > >
> > > >Recorded with a 23 inch Telinga Twin science parabolic microphone in
> an
> > > open
> > > >field with no obstructions between the bell and microphone.
> > > >
> > > >
> > > >Best regards,
> > > >
> > > >
> > > >Jim Morgan
> > > >
> > > >Prescott, AZ USA
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >------------------------------------
> > > >
> > > >"While a picture is worth a thousand words, a
> > > >sound is worth a thousand pictures." R. Murray Schafer via Bernie
> Krause.
> > > >
> > > >Yahoo! Groups Links
> > > >
> > > >
> > > >
> > > Telinga Microphones, Botarbo,
> > > S-748 96 Tobo, Sweden.
> > > Phone & fax int + 295 310 01
> > > email: 
>
> > > website: www.telinga.com
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
>
>
>









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