Ball valve left half opened
Yep, no problem to crank it open. You probably won't notice any or much of a difference, ball valves aren't nearly as frugal as knobby compression valves.

Due to your comment's additional information. A harmonic imbalance was created by the valve's position. Therefore, you need to open it more or all of the way to get rid of the sound. Alternatively, you might have to close it down further to remove the sound as well, but we both hope that's not the sound fix, as you've already noticed a slight flow difference.