Having listened to bells all my life the novelty wore off a number of years ago. Hence my philosophy that bells should be seen and not heard.
That being said however, there are usually rules on each pike regarding bell usage. Interestingly enough, while the bell is almost universally used on locomotives, it is not required to be there by the FRA. One of the pleasures of operating Thomas the Tank Engine is that he is blissfully free of a bell, and therefore he may tiptoe about accompanied only by the soothing sounds of steam and steel.
As to safety, it has been my observation after 37 years in locomotive cabs that the bell is almost invariably ignored and a clear track may possibly be obtained with the whistle and almost surely by the cylinder cocks. Yet more proof of the superiority of steam over diesel.