When recording video with my E-M5, I've noticed I have a weird background noise to all of my videos. It can be heard here. First time, I believed it was the engine of the boat we were diving from, but as I've been taking more videos, I hear it on every video. It's not there when I take videos topside, without the housing.
I've been experimenting a bit topside, and it seems as if the sound comes when the camera is moved. When I'm supporting the housing on my knee, it disappears shortly, but as soon as I'm panning it returns. It seems to be the same whether or not I use stabilizing, so I'd appreciate tips on possible causes and ways to avoid the noise. It's pretty annoying, and I'd like to be able to use the underwater sounds as a background to the soundtrack.
Gear setup: OM-D E-M5 in Nauticam NA-EM5, M Zuiko 9-18mm f/4-5.6, 4" dome port, Inon Z240.