Dean Grantham <>, thanks for this fascinating
report that you sent to Questionbird at the Nature Sounds Society.
I'm posting it on the Nature Recordists mailing list
<> to see if anybody else has
experienced this phenomenon.
Do people at the park say this happens regularly, or seasonally?
-Dan Dugan
Answerbird
*** begin quoted message
Hi--
My wife and I just returned from a trip to the Canadian Rockies
during which we heard loud, ethereal series of harmonic sounds
emanating from two lakes over a period of 5 days. The lakes were both
in Banff National Park: Lake Louise, near the village of the same
name, and Upper Vermillion Lake just outside Banff. We believe we
know the physical source of the sound, but can only guess at the
dynamics producing them.
We're pretty sure the sound was coming from the (approximately 2-inch
thick) ice itself, since we witnessed a very similar sound being
produced at Lake Louise by thoughtless tourists tossing rocks onto
the ice--the ice acted like the membrane of a drum, producing the
eerily beautiful sound. However, during our time there we heard the
ice produce a very similar sound, much more strongly, and heard
it racing quickly from one portion of the lake to another, when there
was no-one else there, no evidence of scree falling from the slopes,
etc. The sounds were pronounced and prolific when the temperature was
well below freezing, and absent when the temperature was close to the
freezing point. This suggested to us that as ice continued to form
and expand, the built-up pressure suddenly released through cracking,
or portions of ice popping up and over other layers, producing the
beautiful vibrations.
However, the mechanism at Upper Vermillion Lake must have been
different--the pond wasn't frozen shore-to-shore as it was at Lake
Louise. (Strictly speaking, the western end of the long narrow Lake
Louise was still clear of ice--elsewhere there was 1-3 inches thick
right to the shore.) At Upper Vermillion Lake, perhaps 30 yards of
open water remained between the ice sheet and shores at least
half-way around the lake, though we believe the far end of the
lake may have been frozen to the shoreline. We spent about an hour
listening to more subtle, yet clear harmonic tones that also seemed
to wander across the span of the lake, but the open water here seemed
to eliminate the possibility of ice pressure being suddenly released.
However, there was a stiff, variable wind coming from the west, and
we wondered if the ice sheet might be slightly lifted because of
reduced pressure (the Bernoulli effect) and subsequently released as
the wind shifted. Perhaps this induced cracking that could produce
the beautiful sound? (There was little or no wind at Lake Louise on
the other hand.)
No-one I spoke to had a ready explanation for the mechanism producing
these sounds. The ice on both ponds was completely clear of snow. In
both lakes the stereophonic effect produced by the rapid migration of
the beautiful sounds from one area of the ice sheet to another was
dramatic and mesmerizing.
Still, we're unsure the sounds were related to cracks forming, or
ice-subduction or whatever, because we didn't ever hear any sudden
"snap" at the onset of the harmonic sounds. Can anyone
confirm/correct our theories about the formation of these sounds, and
has anyone recorded these lovely songs?
Thanks...
Dean Grantham
________________________________________________________________________
________________________________________________________________________
>From Tue Mar 8 18:22:58 2005
Message: 11
Date: Mon, 11 Nov 2002 21:53:33 -0600
From: Wayne Hsu <>
Subject: Re: URGENT request for Pygmy-Owl calls!
Dear all,
Thanks to everyone who sent me suggestions, sound files, and/or comments ab=
out
the new taxonomy. You've all helped me tremendously. I now have all the
recordings that I need for the study. I'm investigating the mobbing respons=
e
of birds in the rainforest to predator calls which 1) all birds have been
exposed to (the Caribbean species), 2) only some birds, namely the altitudi=
nal
migrants, have been exposed to (the highland species), and 3) none or very =
few
birds, probably only longitudinal migrants, have been exposed to (the Pacif=
ic
species). If people are interested in the results of my study, I'd be happy=
to
post a summary on the listserv (if it's not too far off-topic).
Cheers,
Wayne Hsu
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