The Death of a Sovereign
When there is a death of the Sovereign, the bells of the cathedrals are fully muffled. This gives a particular mournful effect, especially when the bell chimes are heavy and mellow. The bells of Bristol Cathedral will sound different now until the funeral of Queen Elizabeth II, apart from Proclamation day where the muffles will be removed and will chime freely for the special occasion.
How The Bells are Muffled
The muffles are leather pads that are fitted to both of the bell’s clapper to reduce the volume. They work by attenuating the bell’s strike note whilst retaining the hum. They are only rung fully muffled for the death of a Sovereign, Parish Priest of Bishop.
Death of a Royal Family Member
When there is a death of a Royal Family member or anyone else important, then the bells will be rung half muffled. This is done by putting the muffle on the side of the clapper that is furthest away from the pulley to muffle the backstroke. And to muffle the front stroke you would put the muffle on the side closest.
You can see in this video here how the bells sounded on the funeral of Princess Diana, who received half muffled bells.