Where does 53.25 and 60 Hz artifacts come from?


Hi all,
I just started recording raw Muse data with Muse Direct and was surprised to see 60 Hz and 53.25 Hz artifacts in the power spectrum. For example, see:

The artifacts and their harmonics are marked with vertical dashed lines.

The 60 Hz artifact must come from devices around me that are plugged into wall outlets, but since the Muse is wireless, I did not think it would pick up much 60 Hz.

Also, I have no idea where the 53.25 Hz artifact comes from.

Can anyone tell me why I’m getting these artifacts and how to mitigate them?

Thanks in advance,