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Re: Amplitude and frequency attenuation vs. distance

Subject: Re: Amplitude and frequency attenuation vs. distance
From: "hartogj" hartogj
Date: Mon May 23, 2011 10:33 am ((PDT))
Hi Jim,
We are often reminded that sound attenuation with distance approximates a r=
eduction of 6dB for each doubling of distance. However, as you and Klas poi=
nt out, the actual attenuation over distance is highly frequency dependent.=
 This suggests the 6db rule would only be accurate at one specific frequenc=
y, 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 in=
cludes a frequency adjustment?

John Hartog
www.rockscallop.org


--- In  Jim Morgan <> wrote:
>
> Thank you Klas for the additional information. Your paper provides much m=
ore
> 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 the
> > >distance to the sound source increases.
> > >
> > >
> > >This effect heard from recordings made of various sounds at different
> > >distances are often noticeable but difficult to clearly hear.
> > >
> > >
> > >Also recordings made with parabolas amplify the higher frequencies mor=
e
> > than
> > >the low frequencies thereby making the recorded sound seem closer than=
 it
> > >actually is.
> > >
> > >
> > >The following test of sound vs. distance is an example of sound amplit=
ude
> > >and frequency attenuation.
> > >
> > >
> > >Here is a description of the test which is the recorded sound of a kit=
chen
> > >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 a=
n
> > 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 Krau=
se.
> > >
> > >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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