jackmc
Killing them softley
Welcome! I think Milky has it. I have Mars II 700 and it's very noisy. If sound was an issue for me I'd replace the OEM fans for better computer fans. But just to warn I usually do thing the hard way.

Noise from led lights is a function of the fans and the housing. If the housing is poorly designed and consructed, it will vibrate and amplify the vibration.
you can beef up a bad design with epoxy to strategically dampen vibration along with quality fans
Are you growing in a tent or a room? I got myself a 2´x 5" silencer for my extraction fan but haven´t tried it out yet!