Yes. No.

Yes: I hear the chime, standing a few feet away from it in the living room.

No: I watch the button press both from from an independent camera (one of an eight camera security system that is not tied to the doorbell system in any way) and the doorbell camera, and can clearly watch while the button pusher stands around looking for the doorbell button, finally pushes it... and the dogs immediately go berserk to a dogs-only signal that nobody else can hear.

Then, after about a five second delay, the chimes ring in the living room and the dogs go even more berserk.

Clearly the button press creates some sound inaudible to humans before the chimes ring. People walking on the sidewalk, talking as they pass the door, do not trigger a response. Both the doorbell camera and the security cameras operate in real time, otherwise I couldn't talk to people on the doorbell system, and I can verify that there is no video or audio delay in the security camera by watching the gardener [should I be upscale and call him the Yard Supervision Manager? 😀] with his noisy tools.

I don't know the details of how the doorbell system is powered, other than it is connected to house current. The wires are buried in the masonry walls and the button/camera is hardwired to the chimes/video-display unit. Probably at the chimes end the current is converted to low voltage (5v? 12v?) DC before being sent to the doorbell button end, but that's just guesswork. Maybe the chimes need more power and there is a delay charging up a capacitor to run them or something.

Anyway, it's all a big mystery to me.

tanstaafl.