<p>The background is measured on the output of the trigger filter. The trigger filter does run downstream of the pre-filter, so is effectively the transfer function of both filters, though mot users would have a wider band on the pre-filter than they do on the trigger filter. This should be clear in a diagram in the online help.</p>

CC BY-SA 4.0
2024-11-13T13:53:24.280Z
2024-11-13T13:53:24.280Z
Doug Gillespie
<p>I have been reading through the PAMGuard help files and was wondering over what frequency range does PAMGuard measure the background noise level in order to trigger a click detection? Does the measure of noise level come from the full frequency range of the incoming audio, or does it come from the pre-filter? For example if the user sets the pre-filter to a bandpass of say 20 kHz, would the noise level be calculated from ~20 kHz and above, or is the pre-filter just filtering the data stored in the click detection itself?</p>

CC BY-SA 4.0
2024-04-26T14:06:40.730Z
does https://bioacoustics.stackexchange.com/questions/1334/does-the-trigger-filter-from-pamguard-eliminate-frequency-components-from-the-or/1336#1336 help you?
WMXZ
CC BY-SA 4.0
2024-04-26T14:33:57.347Z
I had read this post before posting my question and I understand the trigger filter is used to tell the detector which frequency range to trigger on, but wasnt entirely clear if the noise level used for the trigger decision is calculated from the settings supplied by the trigger filter, the pre-filter or the full range of the incoming audio.
TPW
<pamguard><echolocation-clicks>
What frequency range does PAMGuard's click detector measure background noise?
# What frequency range does PAMGuard's click detector measure background noise?

(Asked by: username_0 on 2024-04-26)

I have been reading through the PAMGuard help files and was wondering over what frequency range does PAMGuard measure the background noise level in order to trigger a click detection? Does the measure of noise level come from the full frequency range of the incoming audio, or does it come from the pre-filter? For example if the user sets the pre-filter to a bandpass of say 20 kHz, would the noise level be calculated from ~20 kHz and above, or is the pre-filter just filtering the data stored in the click detection itself?

**Tags:** pamguard, echolocation-clicks

> **Comments:**
> **username_1**: does https://bioacoustics.stackexchange.com/questions/1334/does-the-trigger-filter-from-pamguard-eliminate-frequency-components-from-the-or/1336#1336 help you?  
> **username_0**: I had read this post before posting my question and I understand the trigger filter is used to tell the detector which frequency range to trigger on, but wasnt entirely clear if the noise level used for the trigger decision is calculated from the settings supplied by the trigger filter, the pre-filter or the full range of the incoming audio.  

---

## 1 answers

### Answer by username_2 on 2024-11-13. Score: 0

The background is measured on the output of the trigger filter. The trigger filter does run downstream of the pre-filter, so is effectively the transfer function of both filters, though mot users would have a wider band on the pre-filter than they do on the trigger filter. This should be clear in a diagram in the online help.


---

