Picture 1

0712-2 sound (14s, 112 kb mp3).
A number of buzz-stop sounds followed by a pulse train.
The sonogram shows audio frequencies peaking a 5000 hz in the buzzes and 2500 hz in the pulses. The corresponding (x16) ultrasound frequencies are 80 and 40 khz, resp.

Picture 2

Picture 3

0712-2b sound the pulse train only.
Each pulse is followed by a lower frequency, lower amplitude, trailing pulse.

Picture 4 -- Time axis in audio samples, 32000 samples = 1 sec

Closeup of a single pulse and its trailer. The audio frequency within the pulse is about 6 to 7 cycles per 100 samples, so the corresponding ultrasound frequency is 16*(6.5/100)*(32000) = 33280 hz.