Cap Feeder Noise Control specification should start with the real closure.
Noise can come from the closure material, hopper design, vibration, chute impact and running speed. While no feeder is completely silent, the design can reduce unnecessary impact and overfeed that makes the line harder to operate.
For a better buying decision, the useful comparison is not only hopper size or headline speed. It is how the feeder behaves with your closure, how the capper receives the cap and how easy the line is to run after changeover.
The safest specification route is to start with real closures, target output, line photos and the exact point where the cap must be presented. That avoids choosing a feeder on a generic speed figure that does not match the cap or capper.