Do Androids Dream of Electric Fences?

In my previous posts I have sung the praises of cellphones as portable sound recorders.  We have done some good trials with Android smart phones running the downloaded app "PCM Recorder" - until last week when recording in a farmhouse and getting a rhythmic "click" noise on recordings.

Our farmer hostess suggested "Electric Fence" and we confirmed that after some more tests including a test recording in the nearby town.

This cellphone is a  low-cost Vodafone 858 made by Huawai.  In other tests it has done well in electrically noisy environments which have given trouble to other devices but we now discover that it is vulnerable to electric fences and we will need to be alert about other interference possibilities.

We were filming piano performances with a Sony NEX 5N camera.  Fortunately the on-camera mics did a good enough job, without clicks, but needing a little hiss removal in post.

In images below I have zoomed in on the y-axis to enlarge clicks which have a peak height of -36 dB.