Assignment 5: Acoustic Research

Basically speaking, when designing a space with the purpose of great listening for many people, the ideal environment is a tricky balance between the amount of reverberation required for the event which is emitting the sound. It is all in trying to reduce the amount of sound lost from the original location it had been emitted. The reason a sound gets quieter as it gets farther is because it spreads itself out and "stretches itself thin." This idea is known as the inverse square law (at 10 times the distance, the sound will spread over 100 times the area; the intensity is a 1/100th of the original). On one end of the scale (high reverberation) a sound can carry for a long distance and continue to sound intense even for the people in the back row. On the other hand, low reverberation creates better clarity and authenticity of the sound. High reverberation is usually great for music, while low reverberation is better for speeches.

Reverberation is created through reflective surfaces. The sound bounces its way from the emitting source to the listener in the back. Harder and larger materials have a great reverberation compared to smaller, softer materials which will deaden the sound. The geometry of these surfaces also helps to guide these sounds to their intended ears. A little physics on the idea: if the wave length of the emitted sound is smaller than the surface area it hits, it will be reflected. And obviously the harder it is, the better it will bounce (think of throwing a bouncy ball at different materials: a hardwood floor will work better than a carpeted one). The geometry then comes into play when trying to create an evenly distributed sound. In simple cases, two parallel walls will be very reflective and create a harsh echo while walls angled slightly away from the emitting sound will spread the sound waves throughout the theater. Much more intense geometries can be created to get the sound exactly where it needs to be.

The Allen Theater is one of eight venues in Cleveland’s Playhouse Square performing arts district. Opened in 1921 as a silent movie house, the Italian Renaissance-style building was renovated in 1998, when it began to host large Broadway productions and concerts. It underwent a dramatic transformation from its 2,500-seat format to a more intimate 500-seat proscenium theater. In the new space, designed by Westlake Reed Leskosky (WRL) and opened in September, faceted steel screens created by Toronto-based architectural fabricator Eventscape not only enhance acoustics but also hide or reveal the theater’s traditional interior finishes depending on the desired aesthetic. The walls consist of 300 brake-formed, laser-cut perforated steel screens, each with a unique shape. Three-quarters of the screens are backed with a clear copolymer sheet to reflect sound. Gradient perforations, ranging from 28 percent openness to 46 percent openness at the top, make the screens transparent when lit from behind.