Re: Amplitude and frequency attenuation vs. distance

["Raimund" animalsounds]

> Note that at bat echolocation frequencies the excess attenuation is
> around 1dB per metre, and many bat experts forget how limited bat
> echolocation is, commonly 15 metre max. (120dB SPL at 100mm; -50 at
> 30met total echo path length; absorption -30dB =3D 40dB SPL less
> reflection coefficient. For small targets the inverse square law
> become the inverse quad law.
>
> Lesser horseshoe bats (110KHz)are difficult to pick up at over 5
> metres as I have confirmed at bat emergence counts.

Hi David,

Yes, the atmospheric attenuation of ultrasounds can be huge.

Another problem in detecting bats is that their sonar beam is often quite d=
irectional (http://www.pnas.org/content/107/31/13930.full.pdf).

Also, the sensitivity of most bat detectors is relatively poor at frequenci=
es above about 80 kHz.

Regards,
Raimund