The noise is coming from one of the drains, correct? Not sure if this would be possible, but is there a way to situate the drain tube so that there is no area where water will pool? See crude arrow versus the curve of the tubing in pic:
The drain tube will allow air and water to travel without pooling in the low curved area.
I use to run a drain to a sump using 1.5" clear plastic tubing and it was noisy. It had a curved area much like a p-trap in a sink drain. I moved the sump so that the curve was eliminated and the noise went away as well.
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