So chime is buzzing as motion is activated at video doorbell, voltage at chime and button contacts is 13.35v chime is rated for 16v and video button is auto ranging 10-35v, so within voltage range, just lower at the chime, video is skybell HD and chime is Nutone , transformer is lost somewhere in buried closet ceiling or attic, house has had extensive remodel and owner and wasn’t happy with EC ? From builder. The lower voltage on chime wouldn’t cause chime to buzz?

Huh??

I have absolutely no idea what you are trying to say.

If you are saying you have 13v at the chime and it isn't chiming when the spec is 16, you might have a bad chime ... (unless they are talking about DC in the chime spec)

Trying to find out if it’s normal for camera to activate the chime coil, and/or if the 3volts drop from transformer would cause any other problems, I know we have to find where trans. But the chime buzzing is a annoyance to Home owner, I checked if possible reverse polarity at chime but has no effect?

As Greg said, do you have a bad chime??

The 'buzz' is the coil(s) trying to activate the plunger to 'chime'. Is the chime 'new'? Was it in the home during the renovation? Could be spackle dust, or worse.

Simple step #1 is to try another (known good) chime.

Chime works with single note, assuming it would double strike if receiving full 16volts, just trying to confirm with someone who has done more video button installations, thanks

Most chimes that I have seen strike twice for the front door and once for the back door.
Could you be landing on the wrong terminal?

Sounds like Ghost is on the right trail.

I didn't include that comment, OP did not say it did a single chime, just that it buzzed.

No it’s on the right terminals, just that the voltage has dropped, is why I believe it only has power to strike once.

The skybell video door button, has a motion activated camera and sound, runs through WiFi to cell phones etc, but get power from bell transformer, and seems to be activating the camera, puts humm on chime transformer, just trying to answer if that’s the normal operation of these new video door buttons, manufacturer just says it could be since the chime isn’t receiving full 16 volts? not whether that is normal side effect of video button unit?