The Ears Know: Acoustics, Reflection and Reverberation
Why are some music venues better for concerts than others? Although our eyes may be captivated by the beautifully ornate décor of a historic auditorium or the modern architecture of an avant-garde concert hall, our ears are the truest, best judges.
For more than 70 years, the Wenger Corporation has worked to improve music spaces for both performance and rehearsal. Two important acoustical concepts – reflection and reverberation – play important roles in determining what our ears hear and how good (or bad) a venue sounds. This week’s blog will explore each concept and a related Wenger product designed to positively affect it.
Reflection: Focusing Sound with Shells
Like light bouncing off a mirror, sound waves reflect off hard surfaces inside a performance space including the walls, floor and ceiling. In a proscenium theater, the sounds produced onstage can travel upward into the fly loft space (meant for scenery, rigging and lighting) without effectively reaching the audience.
As a lens focuses light, an acoustical shell onstage surrounds the performers, helps blend their sound and enables musicians to more accurately hear themselves and each other. A shell consists of towers resting on the stage floor and overhead panels suspended from the rigging system. The shell system also helps to project sound toward the audience.
Technology is improving shell design and performance. In the past, manufacturing some custom shells would have required building a model to verify fit and function. Today Wenger can utilize cutting-edge 3-D design software that enables a shell’s complex components to be almost assembled on the computer screen.
The latest acoustical shells, like Wenger’s Diva®, feature extruded aluminum and composite panel construction, offering lighter weight, greater durability and improved flexibility compared to earlier construction materials. For example, Wenger can now create shell panels featuring virtually any curvature an acoustical consultant would specify, aided by a custom-built vacuum press in its manufacturing plant.
Reverberation: Curbing Sound with Banners
Another important acoustical concept for performance spaces is reverberation, which is the persistence of sound in an enclosed space. Sound waves radiate through the air until they strike a surface or obstacle that reflects, absorbs or transmits them. Whatever the sound, reverberation time is measured in seconds, from the moment the sound is generated to when it decays to the point of inaudibility. Key factors that influence reverberation time are the interior surfaces and size of the performance space.
In any performance venue, excessive reverberation can make it impossible for the musicians and audience to hear definition and detail. Notes blur together; articulation and timing become muddy, and clarity is lost. Most professional music venues today are designed to provide reverberation times from 1.3 seconds to 2.2 seconds.
If a certain venue is acoustically “live” – with excessive reverberation – deploying acoustical banners helps absorb sound and reduce the reverberation time. Such banners are a relatively new solution for providing variable, passive acoustics in performance venues. Variable acoustics means the performance space can be tailored to the specific type of performance, whether it’s a large symphony, small ensemble, drama or lecture.
Acoustical banners are typically mounted high on the back and side walls of the audience chamber; an average 2,000-seat performance space might use 20 to 30 banners. Each banner deploys and retracts similar to the operation of a motorized window shade.
When sound waves hit the banner’s absorptive material, the material’s thickness and porosity makes all the difference. Thick, fibrous materials cause sound waves to lose energy by friction. Fabric options with Wenger’s Transform™ motorized acoustical banners include velour, wool serge and quilted polypropylene. Absorbing musical sound is more difficult than absorbing speech because music performance generates more sound energy and usually includes low frequencies that need to be impacted.
For an overview of other acoustical concepts and their relevance to performance venues, free educational guides are available from Wenger, including An Acoustics Primer and Planning Guide for Performance Spaces. These Guides provide general information; we also recommend consulting with an acoustician about your specific situation.