Stop vent clanging with dampers
Often a stiff wind will open vent dampers, causing them to periodically clang shut. If the noise drives you crazy, new spring-loaded backdraft dampers ($9 to $30, depending on the size) should solve the problem. Measure the diameter of the vent pipe and order the dampers from a duct supply company (hvacquick.com is one source). Start by replacing the backdraft damper directly above the vent hood. If that doesn't solve the problem, install a second damper near the wall or roof discharge cap. The second damper will greatly reduce the clanging problem.