There are two separate noises that come from the AC system:
1. The compressor. The electric refrigerant compressor is variable-speed, and has a fair amount of vibration. You will notice the vibration when the unit changes speeds in response to the cooling load. Note that the refrigerant compressor may run even if the cabin cooling doesn't demand it, as the refrigerant is also used to cool the battery/motor/charger coolant loops.
The Tesla compressor is different from other automotive compressors in that almost all ICE refrigerant compressors are variable positive-displacement design that use a variable swash plate and several axially-oriented pistons/cylinders. This design is quiet and can cope with the requirement that an ICE compressor deal with variable shaft speed. The Tesla compressor is a hermetically sealed scroll compressor like a house AC unit. It's far more efficient in terms of amount of refrigerant pumped per watt of power (very desirable in the Tesla), but is inherently noisier.
2. The radiator fans. The two fans in the front of the car may cycle on to increase refrigerant cooling. These fans are loud, and are the same fans your might hear when supercharging. There is also a passive radiator in front, but it can't cool the refrigerant sufficiently in very hot weather.
If you are sitting in stop-and-go traffic on a 95F+ day, expect to hear both sources of noise.
In my case, it is the compressor - which sounds like a noisy old refrigerator.