Smart doorbell, chime is zooming

Hi guys,

I’m trying to make my doorbell smart with @frenck s tutorial:

I have done everything the tutorial says, and everything works, except if i turn on the power switch on the transformer, the chime is making a zooming noise. When i push the doorbell button, it does ring the chime.

Could the problem be related to the relay board, or did i wired it wrong?