Rope and caulk are all you need
Gutter downspouts with elbows can sometimes amplify the sound of water dripping through them, and if the gutter is close to a bedroom window this can get annoying. Contractors have tried fixes like installing a lead plate in the elbow and then a magnetic cushioned plate, but those fixes usually just change the tone from a metallic drip, drip, drip to a thud, thud, thud sound.
Here’s a better way to solve the problem. Caulk around the gutter drain and install a length of nylon or poly rope (Figure A). The water will wick down the rope instead of free-falling and hitting the elbow.