Worx WG520 12 Amp TURBINE 600 Electric Leaf Blower

It's difficult to answer in terms of decibels. I would say louder than a hair dryer and not as loud as a lawn mower. No more loud than any average leaf blower you may have heard before. Hope this helps.

The diameter is 3-3/8", but it will not work with any attachments for the Worx Air Blower. It can work with the universal gutter pro kit, but it may not stay in place as the end of the blower nozzle doesn't have anything that can keep it locked in place to prevent it from sliding off.

Yes, I use it for that. The on/off switch has a variable speed control. As a result, you can vary the blower force so you can gently blow the grass and not the mulch.