During annotation for a passive acoustic monitoring project in India, I noticed that recordings from one particular site consistently show a narrow tonal line at approximately 17 kHz across most files. It appears as an almost constant horizontal band in the spectrogram rather than a biological call.

The recorder used here was not deployed at any other site, so I can't compare it against itself elsewhere.

Has anyone come across something like this before? Any idea what it could be? Hardware artefact, power supply noise, or something environmental?

Attaching a screenshot of the spectrogram for reference.

Thanks!