Dan Dugan wrote:
> I hope someone has some figures on bird SPLs, that would be very
> interesting. I can contribute two points: 1) birds are incredibly
> efficient sound producers, and 2) a typical non-horn speaker is only
> 5-10% efficient.
I think most animals are pretty efficient. They don't have unlimited
energy to devote to it.
As I noted, frogs can be very loud. Reported levels for some have been
in the 120 - 130 dB level, or higher. In fact there is a whole area of
study that's investigating how they don't go deaf. Neat, doppler laser
equipment that can measure the vibration of a spot on a frog from a
distance.
Using my sound meter I've measured sound levels off squirrel treefrogs.
At 3' a single squirrel treefrog can put out around 95 - 100 dBA using
the fast response with hold. And squirrel treefrogs are not
particularily loud, even in large groups. I've been meaning to measure
some of the other species. It's tricky as they tend to start modifying
their calls as you get close.
I do know I've been in frog sites where the entire chorus was loud
enough to pass the threshold of pain. With the nearest frogs being more
than 20' away. I only fairly recently got a good sound meter, so did not
measure those.
What I've been looking for is a good horn pa that's got a decent
frequency range and not too much of a battery hog. I still don't expect
it to get me more than maybe 50 - 100 feet. My 2nd choice is to feed
speakers off my car stereo, where I have more power available.
If I can get some cooperative birds, I'll try and get some readings with
the sound meter. Probably be a while and very hard to get very close.
Walt
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