The venturi restriction plus the short tube going to the sensor was just the right geometry for a good whistle. That was annoying.
I added another pickup tube in the venturi, and connected them. I am thinking this will cancel the waves where they meet.
As a last minute thought I made the geometry not symmetrical as well. That might actually work against me now that I think about it.
Edit: FFF version, the whistle was gone. SLA version failed on first print due to low resin. It will be ready in the morning.