Sony a9 with metabones V canon adapter....noise?? HELP!!

[IslandPhoto]

Forgive me in advance of this has been asked before. I work on movie sets and my camera has to be drop a pin quiet. I'm loving my new a9 with the metabones adapter on my canon lenses. The only problem is if I use the lens at its most wide open, say 2.8, I don’t get any sound. When I use my lens at any other aperture, I get a little electronic sound either when I depress the shutter button completely, in green mode or when I take my finger off the shutter button in advanced mode, using AF-C. Is the lens stopping down and then opening up? Is there anyway to prevent this?  Thanks so much for your time....a little desperate here, if you have any thoughts I'd be most grateful.