The Virtual St Paul’s Cathedral Project enables us to experience the sounds of worship in London’s St Paul’s Cathedral in the 1620’s, even though the building itself was destroyed by the Great Fire of London in 1666.
Our ability to hear sounds recorded in the present as though we were hearing them in physical locations now inaccessible to us is dependent on two processes.
The first is our ability to model electronically the acoustic properties of lost spaces. An acoustic model provides the basic geometry of a space, along with the the acoustic properties of the materials used in the construction of that space.
Sound, once emitted, behaves in predictable ways. If the space in which the sound is heard is an open space, then the sound attenuates over time at a predictable rate as it moves through space. So, the further the hearer is from the sound source, the quieter the sound relative to the volume of the sound at the moment of emission.
If the space is confined by natural or architectural features, the geometry of the space and the composition of the surfaces in the space affect the transmission of sound. Sound, when it encounters an object, is either transmitted, reflected, or absorbed to a greater or lesser degree, depending on the size, shape, and physical characteristics of the materials that make of the surface of objects in the path of the sound waves.
The second is our ability to create recordings of sounds that include only the emitted sound itself, eliminating or minimizing effects of the properties of the spaces in which the sound was recorded. These recordings are called “dry” recordings, as opposed to “wet” recordings, which include both emitted and reflected sound, enabling us to hear the resonances and reverberations of the specific spaces in which the sound was recorded.
The driest of dry recordings are made in anechoic chambers, recording studios whose walls and floor are made of thick, highly absorbent materials. “Anechoic” literally means “without echo”; Ben Crystal’s recording of Donne’s Gunpowder Day sermon for the Virtual Paul’s Cross Project was made in an anechoic chamber at Salford University, in Manchester, England.