There is an adjustment screw on some of them, Chuck and probably all of them. Sometimes you have to take the horn nearly apart to find it, however. Sometimes the horn disk will be broken and occasionally it will be too close to the magnet. There are contact points inside also and sometimes you must adjust / clean those. You can not adjust the pitch of the note, but you can usually make them honk more clearly. But it is time consuming and can be irritating to do this in hot weather. Good luck!
