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Some parameters of the click detector are already set by default in samples. For which sample rate or range of sample rates is PAMGuard designed for?

I have audio files with a 128 KHz sample rate and I’d like to know if this could be a problem in order to detect clicks.

enter image description here

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2 Answers 2

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PAMGuard doesn't have a default sample rate or a default species. The default parameters for click detection should be modified by you to match sensible click separation expectations according to your species of interest and your sample rate. While PAMGuard knows your sample rate, it does not adjust the click detection parameters to match an unknown species/signal of interest.

For example, if your sample rate of 128 kHz and your animal of interest has a click separation of 3 ms, then:

  • 128 kHz is 128,000 samples per sec
  • 128000 samples / sec = x samples /0.003 sec
  • Solving for x gives us: 384 samples

Depending on how relaxed/conservative you want to be, you could set your minimum click separation somewhere around this value (I would go lower, say 200 samples). You can always run your click detection on a sub-selection of data (i.e. just the loaded window) and see how it performs. Play around with the values until you can see that it's detecting the clicks optimally.

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Sample rates do not depend on software, like PAMGuard, but on the signal of interest and are conditioned by the acquisition hardware (analog digital converter in primis, but also disk storage, power consumption, etc)

Given 128 kHz sampling rate, you will have typically a low pass filter of <64 kHz so your signals will only have information in the 0 to 64 kHz frequency range. This will be fine to detect all Sperm whale clicks (< 30 kHz) and at least in part most dolphin clicks, but not porpoise clicks (>100 kHz) and no Kogia clicks (>100 kHz).

To have good quality representation of your received clicks, the sampling frequency should be at least 3 times the highest frequency of interest (the Nyquist criteria: 2 times the highest frequency, is the bare minimum requirement). If you are interested in dolphin clicks and your hardware supports it, you should at least sample with 192 kHz or better with 384 kHz.

If your hardware is limited to 128 kHz, then you can still detect most dolphin clicks, but keep in mind that both the temporal and spectral features are low-pass filtered.

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    $\begingroup$ Thank you for the information. The default settings of the click detector are the ones that appear in the new picture that I've uploaded and they are specified in samples instead of miliseconds. I know that the min click separation between clicks of a Tursiops Truncatus is 3 ms, but to conver this to samples depends on the sample rate. So for a sample rate of 128 KHz , 3ms are 384 samples so I need to change this parameter to 384 samples. Because of that I thought that it PAMGuard had a default sample rate. Maybe min click separation doesn't refer to that concept. $\endgroup$
    – Anaa
    Commented Feb 11, 2023 at 11:19

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