0712-1 sound (4s, 30 kb mp3)
Echolocation pulse train followed by a buzz-stop.
The pulses are emitted around 9 per sec,
and each pulse contains discrete frequencies bands reaching up to 35 khz.
The last buzz contains a broad continuum of frequencies centered on 80 khz
The time vs. frequency plot, or sonogram.
One of the pulses has a bright spot around 2500 hz and the last buzz
is broadly centered between 5000 and 6000 hz.
This corresponds (x16) to ultrasound frequencies of 40 and 80-96 khz, resp.
(The individual frequency bands within each pulse appear to change but this
is in large part due to the detector's directional sensitivity.)
Closeup of 4 pulses from Picture 1.
Smaller secondary pulses are seen to appear between the main pulses.
Picture 3 -- Time axis in audio samples, 32000 samples = 1 sec
A single pulse and its smaller companion.
The frequency within the main pulse is about 6 cycles over 100 samples.
So the corresponding ultrasound sound is 6*32000/100*16 = 30720 hz.
The length of each pulse is close to 200 samples, or 200/32000 = 6.25 ms.
The pulse rate is 4 per 0.5 seconds, or 8 per second.
Seconds 3-4 of Picture 1: the buzz-stop.
0712-1c sound the buzz-stop only.
Picture 5 -- Time axis in audio samples, 32000 samples = 1 sec
Closeup of the end of the buzz and the stop.
Between samples 18900 and 19000 there are 16 cycles,
so the dominant audio frequency in this region is 16*32000/1000 = 5120 hz.
The corresponding ultrasound (x16) frequency is 16*5120 = 81920 hz.