@MichaelS
I suggest you sell your Tesla. I think your expectations are unrealistic. It may be because I'm an engineer, but the "balloon noise" -the high-pitched whine- was instantly recognizeable to me when I heard it on day2 of ownership. I have heard it on other electric vehicles, when getting a ride on them in the airport, or when driving golf carts around the course, or even on my grandmother's electric scooter. When you send max power through a DC->AC inverter, you often get an electrical whine. It's similar to the whine you hear on high-voltage transformers, but they are usually lower frequency, so more commonly described as a buzz. (before people get angry, the sizzling of power lines is something different, I know). Anyway, I've even heard this same whine on my Civic Hybrid when I'm regenerative braking.
Your complaint is like complaining that an ICE engine makes a revving sound when you floor the gas pedal. You may not like it, but this whine is the noise that electric vehicles make when they accellerate at max power. If you really can't stand the fact that your car doesn't meet your platonic ideal of an electric car, then I suggest you eliminate this stress from your life and sell it.
The only time I've heard a car make the noise my car made was the few days that my car was doing it.
I've never heard a golf cart do it nor an electric scooter.
The test drive cars didn't do it.
My car has only done it a half dozen times out of the many hundreds of times I've stomped on the go pedal, and those handful of times was in a span of about 3 days.
If my car were currently doing it, I'd expect Tesla to fix it.
Some distinguishing features about the bad noise my car made vs. the noises other vehicles (e.g., golf carts) make:
1) Sudden onset and cut out while moving. like a light switch. You're going 40 mph, and then wham, it's on, and then you get to 60 mph, and wham it's gone.
2) Pitch is independent of RPM/speed. The pitch started at one frequency and then within a half second dropped about a third to a sustained tone even while the speed of the car increased about 50%.
3) At times it was loud. well golf carts aren't super quiet, but I mean this sound was LOUD.
For what it's worth, my car started making the noise shortly after my parents left. My parents were in town for nearly a week, and during that time I don't think I ever exceeded 200 kW. Right after they left, I started using the car's power and the noise started. After a couple of days of reverting back to making use of the performance I paid for, the noise was gone.
I don't know if that's coincidence or not, but it's a data point.
I also wonder if trying different battery charge thresholds could help.
Derek