The sound you hear is the bio-sonar recorded at Lake Champlain (470 kbs, may take a while to load.)
To compare this sound to other echolocation Dolphin/whale sounds see
This is a spectrograph of the biosonar, taken off of the Dat recorder.
Now for the interesting one... We took a screen shot off of our computer as the bio-sonar occurred, we were datalogging at the time which meant that we were recording up to 200,000 Hertz, or 200kHz.
The color section: x-axis = Frequency (pitch) 4.50E+4 = 45,000 Hz or 45 kHz; y-axis= Time, Color = loudness (amplitude). It looks like the signal does not go any higher than 45 kHz, but that is only because the DAT recorder's upper recording limit is 48 kHz. To get this off of the dat we sampled at 96 kHz.
To compare this chart with a dolphin echolocation go to Risso's Dolphin
Again bottom graph where it says 1D FFT
x-axis = Frequency DC (0) on the left all the way to 100,000 Hertz or 100 kHz (1.00E+5) This in the normal range of biosonar but about 5-10 times higher then normal fish sounds.
y-axis = Amplitude