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A Lesson in Overcoming Acoustic Adversity

People tend to learn by example.

Gaining insight into the problems of reflection and reverberation may result in greater sensitivity and awareness that such conditions can be resolved, in most cases, economically.

For example. nearly 22,000 people can sit in the Staples 950,000 square feet arena. Completed in a record 18 months at a cost of $375 million, Staples opened hoping to be the best of two worlds: sports and entertainment. It was not to be.

As a concert venue, Staples had problems. The sound was inconsistent, there were dead spots and echoes; lyrics (even from Bruce Springsteen, who opened the facility), were often indistinguishable. Acoustically, Staples had to be rescued.

Staples can stand as an example of how to succeed in spite of acoustic adversity. At the outset, the basic structure and design of the building did not prioritize acoustics. Emphasis was on form, function and maximizing revenue. Materials used throughout the building had properties that were highly sound reflective. To illustrate, when sound strikes a surface, a certain fraction of it is absorbed, and a certain amount is reflected. A perfect absorber rates a 1, the opposite extreme is 0. So look at the materials used and think about your own buildings as well.

Sound Absorption Materials used at Staples:

• 2,500 tons of structural steel .01-.02
• 73,000 cubic years, concrete .02
• 2,865,000 sq ft of drywall .04-.06
• 81,000 ft of Terrazzo tile .01
• Heavy plate glass .03
• Heavy carpet on concrete .37
• Fiberglass acoustical panel .80

Reality is that traditional building methods fail to provide for the acoustical control of sound.

3. Staples management knew they were going to have a problem but they couldn’t assess the “how big” until the building opened. They were dedicated to achieving a quality sounding facility. Barbara Streisand was in the performance line-up.

4. Call in the experts. Upon advice from sound engineers and acoustical consultants, attention focused on 50 sections of very long, polished concrete walls. They formed a perimeter behind seats on the primary two levels. surrounding the arena.

Look again at the numbers above. What was the percentage of sound reflected? If you answered about 98%, you’re on target.

As pictured, construction began here. Anchors secured hundreds of feet of narrow wood onto the concrete surface, preparing an easy base mount for Fabric Wallmount System’s, Wallmate. With base mounting in place around the perimeter of each concrete partition, acoustical fiberglass panels were installed and then covered with Dacron padding. An acoustically transparent fabric was installed (“railroaded”) horizontally to minimize seams. When mounted on Wallmate’s outer track, fabric was aligned, stretched, tensioned drum tight and locked in place. Management knew that if needed, service, repair or a complete change out of fabric could be done by in-house staff. The fiberglass was a dense one inch rigid panel. Look again at the acoustical gain. Did you come up with a .80? Approximately 80 % of sound was absorbed using this method.

5. The experts knew that reverberation and reflectance were the issues. “We need to take the room out of the equation… and keep the dominance of the speakers intact.” stated one engineer. At 125,500 watts of audio amplification, this was not easy.

6. The aggressive assault on reflection and reverberation targeted everything. The massive span of bare steel superstructure (very low .01, .02 numbers) required nerves of steel by those who installed a variety of specialty devices: Perforated aluminum enclosures held heavy acoustical fiberglass in a vertical position over upper level seat sections; perforated vinyl balloons containing acoustical batting (.80+) were installed to conform around a multitude of support and operational structures. Suspended below the huge expanse of ceiling, heavy acoustical banners served to intercept and reduce reverberation. The arena was virtually draped with acoustic material.

All told, reflection and reverberation were show stoppers. Aggressive management response created an exceptional makeover. The result was exemplary.

Barbara Streisand, by the way, had a breathtakingly beautiful concert and Los Angeles acquired a world class entertainment facility, a happy ending.

Worship facilities of all sizes can benefit from low cost, acoustically effective products. Some materials are available direct. Some installations require only basic skills and use of ordinary tools. Acoustical or engineering advice is often advisable since structures, materials, shapes and equipment specifications vary. For more complex facilities, the use of computer modeling to factor in most variables are an impressive state of the art resource.

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