Page 29 - Winter 2011

FROM SPORTS ARENA TO SANCTUARY: TAMING A TEXAS-SIZED REVERBERATION TIME
Russ Berger
Russ Berger Design Group 4006 Belt Line Rd. Suite 160 Addison, Texas 75001
Creating a new home for America’s largest church required a facility conversion of unprecedented scale. Over a period of 19 months, Houston’s Compaq Center—a sports arena that had been home to the Rockets NBA Basketball team, Aeros hockey team and other Houston sports legends—was transformed into Lakewood Church, a new 16,000–seat worship center for its 47,000 weekly congregants.
Lakewood’s weekly television program is seen in more than 20 million households in the United States and is received by more than 200 million households in more than 100 countries. As one might imagine, there were significant hurdles in converting a sports arena into a house of worship with a major in-house broadcast center—acoustics and noise control being some of the most challenging.
A space that is appropriate for hockey and basketball needs to support hubbub and crowd noise while allowing the sound of sports announcers to ride on top. As you watch a sports event, there are score boards, video feeds, and announcements supporting the live action. In this type of space, speech articulation and the loss of consonants are low on the list of critical functions. If you miss a few words or even an announcer’s entire sentence, you still can “get” what is going on. It’s a noisy space by nature. For this use, the Compaq Center’s existing acoustics were up to the task.
At the other end of the performance spectrum are spaces designed for worship. Here, the goal is to project each nuanced word, both spoken and sung, to every seat in the house so that each member of the congregation has an inti- mate experience with the message. Worship spaces need to be quiet and acoustically appropriate. Delivering a renovated space that would meet these new criteria was one of the pri- mary challenges in repurposing the sports arena.
The conversion required significant changes to the acoustics within the space along with modifications to make it a much quieter venue. To support both natural-sounding speech and Lakewood’s wide-ranging program of musical styles, the first acoustical priority was controlling the low fre- quency energy in the sanctuary.
As a clear span structure that would hold 16 thousand fans, the arena building was originally designed with a curved roof section that tends to focus sound. Prior to the renovation, non-linearities in the low-frequency response, focusing from the roof deck and end walls, and specific sur- face reflection paths caused the bass frequencies to build up, making the sound dramatically different from seat to seat and virtually unintelligible in places.
“When this building was used for hockey or basketball, hearing the score through the crowd noise was the only requirement.”
The Arena of the Compaq Center, before it became the Sanctuary of the Lakewood Church (Fig.1), was known among touring companies as a trouble- some venue with generally uncontrol- lable low-frequency performance. From 250 Hz down, the average reverberation time, taken from dozens of measure- ments throughout the space, clocked in at more than 5 seconds and in some areas more than 10 seconds at frequen-
cies below 150 Hz. This was not a happy place for kick drum and bass guitar, with sound from last week’s performance seemingly still rolling around the arena.
The new sanctuary also had a variety of noise and vibra- tion issues. Noise that would have been unnoticed during a basketball or hockey game would be intolerable during a worship service. Increased sound isolation was needed from the concourse (Fig. 2), from the new chiller plant, and from traffic on the freeway just outside the building.
After studying a wide variety of options to tame the long, low-frequency reverberation times, a combination of treat- ments were employed. Low-frequency absorption was added over the arena’s former sky boxes. To reduce low-frequency crawl across the dome structure, the area above the main floor was covered with acoustically absorptive lapendary banners. Suspended from the existing structure, these ban- ners are obstructed from view by acoustically transparent architectural elements below that create the visual ceiling. Control of specific reflection paths from the main clusters was addressed through distributed treatments.
A solution to overcome the narrow-band, low-frequency reverberation time issues via under-seat return air openings germinated from a site visit to work on the heating, ventilat- ing and air conditioning (HVAC) modifications necessary to meet code requirements. While sitting in the stands, light from the exit concourse windows overlooking the adjacent freeway could be seen pouring in through the slots under every seat across the empty arena. (see Fig. 3.) A method to use these slots as a tuned Helmholtz absorber was devised. Creating new slots in the concrete risers at every seat would have been cost prohibitive—but they were already included as a part of the original construction. The slots had been venting return air from the air conditioning systems into the common egress space, a technique that no longer met fire code. While this was still the best philosophical solution to meet return air needs, under-riser plenums would need to be added. The new fire separation scheme for the sanctuary required that a barrier be constructed beneath the arena seat- ing. Nursery spaces and children’s classrooms for teaching
From Sports Arena to Sanctuary 25