Assignment 5: Acoustics Research

Reverberation, simply put, is the prolongation of a sound. It is the collection of reflected sounds from the surfaces in an enclosed space.This means that the higher the number of times sound bounces around the interiors of a solid space, the higher the reverberation of sound in that space.

It is important to understand the range of prolongation that classifies as desirable reverberation. Reverberation times below 1.5 seconds and above 2.5 seconds either absorb too much of the sound or too little of it. 

 The way sound travels in the enclosed space relates to the dispersion of the sound waves. This dispersion of waves, unless controlled, excessively amplifies sound or creates unwanted echoes. The general solution to avoid such a problem is avoiding the use of reflective surfaces in the space on a large scale.  A great example of acoustic architecture is the MIT Chapel by Saarinen. The outside form of the chapel is a simple, continuous cylindrical brick structure, supported by a series of low arches. 

On the inside this cylindrical structure is offset and doubled with a slight modification- the interior walls are undulating brick. 



The surface that the brick pattern creates is perfect for achieving the ideal reverberation in that intimate interior space. One can actually experience the slight echo if he or she speaks, standing in the center of the room. The double width of the walls not only insulates the interior from the noise outside it, but also allows the interior space to become a space where sound waves emitted from the altar space are amplified just enough to be heard well throughout the interior space. The ceiling is also a 3d surface, made out of a plaster like material that allows the ceiling to contribute to the reverberation of sound.

"Saarinen stated that "since it [the chapel] is built largely of masonry, it should sound that way." However, Saarinen did allow for music and speech to be heard clearly. When the chapel is empty, the reverberation time at 500 cps is about 300 seconds. With an audience of 115 people, the reverberation time is only about 1.8 seconds. The hard plaster ceiling also helps to spread sound with its inverted cone shape. Red brick is used and gray,leaded glass in the narthex. (The chapel’s aluminum bell spire was sculpted by Theodore Roszak.) "

Sources: 

http://kubuildingtech.org/sarcweb/Assemblages00/CaseFinals/Lena%20Coleman-Kresge%20Chapel/Eero%20Saarinen-Bio.htmlhttp://www.acoustics101.com/default.asp

http://en.wikipedia.org/wiki/MIT_Chapel
www.acoustics101.com