Below 37 F faint humm that starts at 10mph and stops at 7mph

What I know so far with the 2017 Prime Plus trim. It's a very faint hummm that is hard to hear unless there is no other noises. It has to be below 37 F or when the temp display next to the speedo blinks the temp reading for 10 seconds just after putting the car in READY mode. The hummm is barely noticable at 10 mph and is really hard to hear above 12 mph because it blends in so well with normal road noise from the car. It's most noticable when it shuts off at 7 mph when gliding to a stop from 10 or 12 mph.
Yesterday it was 38 F here and the car didn't hummm at all at 10 mph, like it did today with a temp of 34 F.
Same humm I've heard as in years past between 7 and 10 mph when temps are below 37 F.

I've been using Pre Conditioning both yesterday and today and I've had no issues using Pre Conditioning several times in a row while plugged in Charging. Yesterday at 38 F it even felt a tad warmer when I got in the car. Today after 3 Pre Conditioning 10 minute sessions in a row before driving, I felt no warmth inside the car.

I think the hummm is the heat pump, but since I don't have much info about how and when the heat pump actually runs, I can't say for sure that's whet the humming sound I'm hearing is from.