Acoustical Shells 101: Super, Sonic Connection
From an occasional series…
To understand the benefits of acoustical shells in music performances, first consider typical auditorium architecture: stage and audience area separated by a proscenium opening. While this setup is ideal for drama, it poses acoustic challenges for music.
Separated Spaces. The proscenium opening separates the stage and audience, creating two different acoustical spaces. Instead of reaching the audience, much of the sound produced onstage gets lost in the fly loft or wings. Musicians find it difficult to hear themselves and each other; sound to the audience is also diminished.
Wanting Better Sound. “Our music faculty overwhelmingly asked for ‘better sound’ when we were planning the Talbot Theatre’s renovation,” recalls Louis D’Alton, Concert Manager at the University of Western Ontario (UWO) in London, Ontario. Built in the 1960s, the Talbot featured a fly loft and rigging system above the stage. “Acoustics were our primary consideration,” notes D’Alton, adding that the room’s small size meant the sound was often overpowering.
Room to Grow. Auditoriums require sufficient cubic volume to create the desired reverberance for pleasurable listening. Inadequate cubic volume results in excessive sound energy that makes listening difficult – even painful – for musicians and audience. Acoustical shells cannot fix a lack of cubic volume.
“The volume of the Talbot Theatre was far too small,” comments acoustical consultant John O’Keefe, Principal with Aerocoustics Engineering Ltd., Toronto. “It would never be reverberant enough at its existing size.” The room’s ceiling height was raised 13 feet, increasing its cubic volume by 20 percent.
Spaces Connected. Acoustical shells help connect the stage and audience areas, creating one larger acoustical space. Most acoustical shells consist of two elements: sound-reflective side and rear towers surrounding the performers and ceiling panels suspended from the rigging. Together, these elements seal off the backstage and above-stage areas, minimizing sound leakage and maximizing sound projection across the ensemble and to the audience (Figure 3).
Multiple Benefits. The convex shape of the shell towers and ceiling panels scatters the sound; the shell’s materials provide acoustically reflective surfaces effective across a broad range of musical frequencies. Musicians can hear themselves and each other better. While the shell creates a “blending chamber” for sound on stage, it also helps reflect sound to the audience. Studies have shown that shells increase the strength of sound by more than 3 decibels at many seat locations – approximately equal to doubling the performing group’s size. Onstage effects are even greater — more than 5 decibels.
Amazing Transformation. UWO faculty have praised the acoustical shell’s role in the renovation of what is now called the Paul Davenport Theatre. “The transformation is nothing short of amazing,” exclaims Robert W. Wood, Ph.D., Dean in the UWO’s Don Wright Faculty of Music. “A 45-year-old acoustic nightmare has been changed into a beautiful and acoustically superior performing space.”
For more information about acoustical shells and other related topics, Wenger Corporation offers various resources, including a free 34-page planning guide outlining basic acoustical principles impacting many common performance spaces, along with a list of other resources.
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