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Acoustics for Different Worship Formats
By: Thom Mullins

Bethany Community Church serves the community around the Green Lake neighborhood of Seattle. In addition to local residents, students from the University of Washington and Seattle Pacific University attend worship services. The church, formed in 1916, provides worship services that range from a more formal worship experience, which includes a choir and an electronic organ on Sunday mornings, to more contemporary worship reminiscent of Cold Play on Sunday evenings. They moved into their old facility in 1969, which served them well into the beginning of this century. However, they were beginning to outgrow the facility and decided to build a new facility on property to the west of their original sanctuary.

The church had several goals in mind for their new building. The first was to provide adequate seating for the congregation, which had grown from 300 to almost 800. They also wanted the architecture to reflect not only their theology and relationship with God, but also the environment of the Pacific Northwest. The sanctuary was to be open and expansive and reflect the use of natural materials as much as possible. In response to this, the architect designed a sanctuary with a 35-foot-high ceiling using natural wood for the interior surface finishes.
In addition, the church's technical team wanted to move from their existing analog sound system to a digitally based design that would provide the flexibility needed to support the wide variety of worship styles and respond to future ministry opportunities, such as movie nights and contemporary Christian music concerts.

The sanctuary is a large box, roughly 80 feet long, 50 feet wide, and 35 feet high with a balcony and a "tip out" on the south wall. With the architect and the owner committed to an expansive feel in the sanctuary, the ability to shape the side walls to project sound from a choir into the sanctuary was very limited. In fact, the back wall of the stage rose straight to the roof structure, preventing installation of any overhead reflector panels, which would have also helped to project sound onto the congregation.

The biggest issue was finding a balance between the two extremes of worship style. More traditional worship requires a longer reverberation that supports the use of unamplified instruments and voice. These longer decay rates work to blend voices and instruments together into a harmonious whole. This is the exact opposite of what is required for a contemporary worship service, in which shorter reverberation times helps to keep the overall volume of sound lower and increases speech intelligibility. Both of these extremes must also be balanced against the needs of the congregation to experience participatory worship. Far too often, the congregational acoustical environment seems too dead and they feel more like spectators than active participants in worship.

In this instance, the choice was made to go for a shorter reverberation time overall. In part, this was in response to the accelerating move towards more contemporary worship. While the horizontal wooden slats provide a great deal of reflective surface, space behind the slats is filled with absorbent material on the lower half of the wall surface. The upper half and the ceiling was left untreated, providing a reasonable balance for most parties. The front wall of the sanctuary, behind the platform, remained hard and reflective, which helps support the choral and unamplified instrumental uses of the space. This also works to provide a large reflective surface that strengthens the sense of ensemble during congregational singing.

While the acoustic environment was relatively easy to work through, the sound systems and visual presentation systems presented more of a challenge. It is vital for the architect to understand the differences in worship style and what that means for integration of the audiovisual systems into the space. As we discovered the needs of the worship director and the technical team, we found a disconnect between the technical needs of the project and the architectural statement. This was most obvious after we created our computer model of the room and shared this with the architect. Our design approach called for Left/Center/Right clusters with subwoofers to cover the congregation and the architect's image was of pew-back loudspeakers or speakers mounted flush in the ceiling. Once we explained the difficulties and agreed to use black loudspeakers, we were able to work this out to our satisfaction.
The other major concern was the video presentation system. Our initial sightline studies revealed the need for a large image 156" wide by 120" tall.  We initially discussed a large electrically operated screen, but this would have created a major issue architecturally by placing a large box across the front of the sanctuary.  The architect and the owner were very committed to keeping this as clean as possible. We were able to suggest flattening a portion of the wall (there was a slight curve that had no appreciable acoustical impact in the sanctuary) and using a special paint on that portion of the wall as a projection surface. The architect contributed the idea of anchoring the upper right portion of the image by using intersecting pieces of burned steel along the upper and right hand sides of the projection surface.  The result was a stunning image.

Bound up in this was the location of the video projector. Again, our calculations would place this in the technical booth, right next to the audio engineer, which was not a good idea given the high noise output (42 45dBA) of a very bright (10,000 ANSI lumens) projector. The solution was to bury the projector in the face of the balcony, taking advantage of one of the architectural portholes to shoot through. We were also able to hide a couple of remotely controlled production cameras elsewhere in the balcony face. It did require placing a service hatch below the projector and actively cooling this area, but this was done at minimal cost and utilized the existing wooden ceiling panels as part of the solution.

In the end, Bethel Community Church ended up with a facility and technical systems that exceeded their original goals and will grow with them as their congregation and needs change over time.

Thom Mullins is a senior consultant with BRC Acoustics + Technology Consulting in Seattle, www.brcacoustics.com.

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