I bought a Zmodo Ding Home Package. It came with a Greet Doorbell Wi-Fi Camera, Beam Wi-Fi Extender/Smart Hub, 2ea Door/Window Sensors, and a Power Accessory. Like the writers on this thread have stated, I too was having issues with my reliable 25 year old chime developing an annoying humm/buzz after installing the Doorbell Camera. My old system had a NuTone Chime powered by a 5VA/10V transformer.
I don’t agree with the “voltage mismatch theory”. I believe because the standard doorbell setup leaves the circuit "open"when the button is disengaged, the coils in the chime are not powered/energized. This keeps the chime off and “quiet”. When the doorbell button is pushed, the circuit is completely closed causing the chime to operate normally. Even most lighted doorbell buttons draw so little current that the chime coils are not powered/energized and are not affected.
The Greet Doorbell Wi-Fi Camera on the other hand “slightly closes” the circuit when the doorbell button is disengaged. Although not completely closing the circuit, there is enough current drawn to “slightly” power/energize the coils in the chime. This causes the humm/buzz in my 25 year old NuTone Chime.
I tried the supplied Zmodo Power Accessory too. Stopped humm/buzz, but also stopped chime from working. I even replaced my 25 year old 5VA/10V transformer with a new $15 10VA/16V transformer. No difference in performance…
My next shot was to replace the chime. I did so by exchanging that new $15 transformer with a $17 Utilitech Doorbell Kit. The kit came with a new chime, 10VA/16V transformer, and two lighted door buttons. I installed the new transformer and chime. The humm/buzz is drastically diminished! If the house is completely quiet (no refrigerator running, A/C heat pump on, etc.) you can barely hear the humm if you tried hard. I highly recommend anyone with an old humming/buzzing chime to try replacing it with this Utilitech. It worked for me.
FYI - I had to perform touch-up painting as my new chime has a smaller footprint than the old chime.