AC/Generac Transfer Switch

All switches put noise on the line when they break contact. The transfer switch won't be a problem when closed against utility power.

You cannot use a subpanel at the service anymore if your local building department uses the 2020 NEC. That panel will have to be a service entrance rated panel (load center) with a main breaker disconnect or a switch in a separate enclosure ahead of the panel if it's not a load center. 

I would say talk with your electrician, but if he installed more than one ground at your house I doubt he's got a license.

I have a 200 amp service and a 100 sub panel and they both share the same ground. Did your electrician say why you needed a second one?  Did he charge you for the second one?

Several of us are very curious.

@dpop It is an electrical noise. It is a steady buzzing sound like an electronic bee. Music playing will obscure it but it is very annoying between tracks.

I also learned the hard way that I should not have placed the generator outside our bedroom. The mechanical noise is irritating especially when it cycles under load.

Friends installed their generator out of site on the side. Prevailing winds blew CO into the house. The wife ended up in the hospital.

Ensure the install cannot kill you. Electrically or otherwise.

+1 on the multiple ground question. It's generally a bad idea.

See Ground Rod Theory Installation

Here is one method for feeding the audio room audio equipment power outlets ahead of the ATS.

A Combo meter socket / with main breaker with a small circuit breaker load center. The bus has feed-thru lugs that would feed the normal, (Utility Power), to the ATS.

A breaker would be installed in the panel to feed a sub panel in the house for the audio room audio equipment outlets.

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