Those magical days when the HVAC is off

My heat pump / air handler is about 25 feet from my audio system in an enclosed room that is well sonically insulated. I also have a variable speed air handler and pump so, is if the house is only slightly warm… it is on very low and barely running.it is not at all obvious it is running.

That said, when running at all it increases the ambient background noise from the high 20db range to the mid-thirties… and negatively effects listening. What is amazing is that it does not just effect really quiet passages… it effects all but really loud ones. I am not hearing any electrical effects, just the increase in the background noise level.

My air conditioning system can be remotely controlled on my iPhone. So, I will temporarily turn it off while listening. Or even pre-cool a bit before a listening session.

I use an oversized iso transformer (10kVa) for my main system, which draws very little current. The AC system also has variable speed compressors, not just variable speed fans, so once set temperature is reached, the compressors wind down and function as dehumidifiers. I’m in Central Texas, where air conditioning runs pretty much constantly. Until the building boom here, the grid was not only more stable, but very quiet. It is still quiet compared to where I lived in the lower Hudson Valley (old infrastructure) but much more "iffy" with the demands now being placed on it. FWIW, the outdoor air compressor units are at the opposite corner of the house from the listening room. 

We just finished installing a large 26kVA back up generator, and I had the contractors wire it in such a way that the electrical subsystem for the main hi-fi is not connected to the ATS for the generator (in other words, the system will not be powered by the generator if the utility power goes out). None of this came cheaply, but was worth it in my estimation for peace of mind. Given that my speaker system is 104db sensitive, I can hear any power or grounding anomalies and it is dead quiet.

The other aspect is ambient noise in the listening area. I measure around 32 db C weighed during the day. I can do more to quiet the room by using soundproofing, not just acoustic blinds, on the dormer windows facing the street, but usually don’t bother. I do not use "power conditioners" or noise trapper type tweaks, as such. The house is also very well constructed, old, longleaf pine and when it was restored, the insulation used (shredded denim in netting) was installed. Room to room dialog is almost impossible because of the construction/insulation methods. (Walls are shiplap, not just drywall).

PS: AC Infinity makes duct fan silencers if you hear air rush through your vents. I first got onto that company when I had a silencer box built for the air compressor that drives my tone arm. I was able to put together a relatively inexpensive fan cooling system with central panel and sensor for inflow and exhaust fans for the silencer box. Now, it appears that they are big on leaf growing equipment. Go figure, as they say in Jersey.

Same here.  I shut down all the ac systems when I listen.  I don't know if it is the sound from air through the vents or noise on the AC lines.  Big difference.  Same as GHD, I cool down (or heat) the house before listening then shut it all down.  

I have VVT dampers in ducts. Air handlers are in the attic (2 story house) listening room is on the 1st floor. avg 38db with AC on. quite in comparison to some. 

The lowest ambient noise levels I can achieve in listening room is low 30's on quiet nights, this living on relatively quiet street, traffic is the worst for ambient noise levels. Daytime 50's and above. I can only imagine what I'd hear with something like low 20's. I'd suggest using resources to improve one's home and listening area to achieve lower ambient noise levels is equal to or better than using those resources to purchase a new higher resolving component.