The Sturmey Archer hubs I've ridden all become rattly as soon as a little play develops (which I think is mainly a result of the ball ring being tightened by pedalling force); dialing out that play by adjusting the LH cone ought to solve the problem. However, it sounds as though your hub could use a full service / overhaul, as is wise to have done every few years and particularly after the initial wearing in phase.