method to detect frequency sweep in audio
If you know the signal of interest in advance, you can pre-record it and constantly calculate correlation between recorded sample and incoming signal.


Record a sample sound from a channel to be analyzed (you can record a number of periods)
Reverse it
Use reversed signal as an impulse response for FIR filter (this also is known as "matched filter") -  filter will output a peak when signal of interest passes through it.


If you are interested in general varying tone detection (much more difficult problem), look at the chirplet transform - the sort of wavelet transform which uses varying frequency wavelets (chirplets) as its basis. People used it to count wolf howls, for example.