Rapping is a phenomena long connected with poltergeist activity. 'The Rochester Rappings' at Hydeville in 1848 became one of the most famous cases, leading to the development of modern Spiritualism. As the phenomenon developed, rapping remained the main way of contacting spirits for some time. In fact, it still has a place in séances to this day, although more advanced methods of communicating have come into play too.
Raps have often varied in volume and clarity from case to case, and can take the form of a thud, clear sounds or vibrations. There is evidence that raps can be created by humans through their joints, so many believe the variation in sound can be due to the area used to create the rap. There have also been examples of special medium tables developed especially to rap.