I was looking for some meter that can tell me how many decibels a frog
emits at a distance of 10 meters etc, (assuming that's the loudest
thing this still night). All I can find are meters that start at 30
dB. Perhaps I'm searching in the wrong category?

"Dan Jacobson" wrote in message

I was looking for some meter that can tell me how many decibels a frog
emits at a distance of 10 meters etc, (assuming that's the loudest
thing this still night). All I can find are meters that start at 30
dB. Perhaps I'm searching in the wrong category?

Perhaps you're looking at SPL levels that are too close to the noise floor
of common mics.

There are research papers on the subject if you want to go that route.
I've included one such at the bottom of this post.

If you are intent on measuring I would suggest using a parabolic
reflector with a microphone. The larger units have over 50dB of gain
(you can record bird calls from over a mile away). A cheap reflector
and microphone capsule runs about $200. Common professional units are
the Dan Gibson reflector and Roch=E9 parabolas ($1000 and up). You
probably would have
to calibrate the rig to get accurate data.

Excerpts from "Frog Auditory Behavior" by David D. Olmsted. Full paper
at http://tinyurl.com/3mlyq

The sound level (RMS measurement) of mating calls for most frogs and
toads is between 100 and 85 dB at 50 cm (Gerhardt - 1975). Mating call
intensity levels needed for discrimination for the frog Hyla cinerea
were determined by Ehret and Gerhardt. Using a 900 Hz tone , the mating
call must be an average of 33 dB more intense than a 55 dB noise
background, 40 dB more intense than a 65 dB noise background, and 45 dB
more intense than a 75 dB background (Ehret and Gerhardt -
1980)....the ear's output neurons have a nearly continuous range of
intensity thresholds, much more than is needed just to maintain a large
dynamic range from 0 to 100 dB.

Gerhardt, H.C.(1975) Sound Pressure Levels and Radiation Patterns of
the Vocalizations of Some North American Frogs and Toads. J. Comp.
Physiol. 102:1-12

Ehret, G. and Gerhardt, H.C. (1980) Auditory Masking and Effects of
Noise on Responses of the Green Treefrog (Hyla cinerea) to Synthetic
Mating Calls. J. Comp. Physiol. 141:13-18

There are research papers on the subject if you want to go that route.
I've included one such at the bottom of this post.

If you are intent on measuring I would suggest using a parabolic
reflector with a microphone. The larger units have over 50dB of gain
(you can record bird calls from over a mile away). A cheap reflector
and microphone capsule runs about $200. Common professional units are
the Dan Gibson reflector and Roch=E9 parabolas. You probably would have
to calibrate the rig to get accurate data.

Excerpts from "Frog Auditory Behavior" by David D. Olmsted. Full paper
at http://tinyurl.com/3mlyq

The sound level (RMS measurement) of mating calls for most frogs and
toads is between 100 and 85 dB at 50 cm (Gerhardt - 1975). Mating call
intensity levels needed for discrimination for the frog Hyla cinerea
were determined by Ehret and Gerhardt. Using a 900 Hz tone , the mating
call must be an average of 33 dB more intense than a 55 dB noise
background, 40 dB more intense than a 65 dB noise background, and 45 dB
more intense than a 75 dB background (Ehret and Gerhardt -
1980)....the ear's output neurons have a nearly continuous range of
intensity thresholds, much more than is needed just to maintain a large
dynamic range from 0 to 100 dB.

Gerhardt, H.C.(1975) Sound Pressure Levels and Radiation Patterns of
the Vocalizations of Some North American Frogs and Toads. J. Comp.
Physiol. 102:1-12

Ehret, G. and Gerhardt, H.C. (1980) Auditory Masking and Effects of
Noise on Responses of the Green Treefrog (Hyla cinerea) to Synthetic
Mating Calls. J. Comp. Physiol. 141:13-18

There are some around. For something good, you will have to dig very deep in
to the big bucks. A discent sound meter is very expensive, just like a good
DVM, and others alike.

Brüel & Kjaer
http://www.trsonesource.com/trs/cont...er_c06.asp#B&K



--

Jerry G.
=====



"Dan Jacobson" wrote in message
...
I was looking for some meter that can tell me how many decibels a frog
emits at a distance of 10 meters etc, (assuming that's the loudest
thing this still night). All I can find are meters that start at 30
dB. Perhaps I'm searching in the wrong category?

"Jerry G." writes:

There are some around. For something good, you will have to dig very deep in
to the big bucks. A discent sound meter is very expensive, just like a good
DVM, and others alike.

The $6000 B&K we have at the acoustics lab at work (Sony Ericsson)
only goes down to about 20 dB SPL.

--RY


--
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%%% 919-577-9882 % til then, I'll leave her alone."
%%%% % 'Yours Truly, 2095', *Time*, ELO
http://home.earthlink.net/~yatescr

Jerry G. wrote:
A discent sound meter is very expensive
Yes, but a working spell checker is quite affordable.

Dan Jacobson wrote:

I was looking for some meter that can tell me how many decibels a frog
emits at a distance of 10 meters etc, (assuming that's the loudest
thing this still night). All I can find are meters that start at 30
dB. Perhaps I'm searching in the wrong category?

Unless you are looking at Bruel & Kjær perhaps? - but even 30 dB is
awfully silent meterwise and you probably can not - at least not by
meausurement - isolate the frog from the background noises from the
vegetation, at least not at that measuring distance. You are likely to
have to be closer to be certain that what you meausure is what you think
you measure. Try re-asking over in alt.sci.physics.acoustics .... this
is their turf and someone over there may be able to supplement.


Kind regards

Peter Larsen




--
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