Back in 2017, architects laid out their dream design for the Space Needle’s $100 million renovation project, featuring a sleek, modernistic interior, floor-to-ceiling glass windows, glass benches and a glass floor that would make a complete turn around the needle’s axis every 45 minutes.
But for Daniel Bruck, the president of Seattle-based BRC Acoustics & Audiovisual Design, there was a chance that the dream could turn into a noisy nightmare.
“That was a very interesting challenge for us,” he said today at a news conference during the Acoustical Society of America’s Seattle meeting.
Out went the sound-deadening carpet and plush furniture in the restaurant of the 605-foot-tall Seattle landmark — a holdover from the 1962 World’s Fair attended by millions of visitors, including Elvis Presley. In came sound-reflecting floors, ceilings and walls that had the potential to raise the decibel level to rockabilly proportions.
And as if that wasn’t enough cause for worry, the steel-on-steel gearwork that set the floor revolving could have introduced a whole new source of mechanical noise.
Bruck acknowledged that the renovated space has a “clean and elegant” look. “But from an acoustical standpoint, it didn’t give us a whole lot to work with,” he said.
Hitting the project’s targets for noise reduction required a combination of sound acoustical design, some special tricks of the trade and a little bit of serendipity.
It turned out that the grinding of the gears wasn’t as loud as Bruck initially feared — partly due to how slowly the floor revolved, and partly due to the insulating effect of the 10 layers of glass between the machinery and the Needle’s 500-foot-level lounge, known as The Loupe.
“Both of those things contributed to that being a non-issue from a noise control standpoint,” Bruck said.
BRC Acoustics’ engineers also found a way to put extra noise-reducing material on the ceilings below the mechanical equipment.
“Then we had to get creative,” Bruck said.
Some of the tricks of the trade involved finding new ways to channel the air being moved around by the renovated Needle’s heating, ventilation and air-conditioning (HVAC) system.
“We had to introduce new return plenums, for example, with lining in the plenums directing the air in a direction it might not have gone otherwise,” Bruck said. “We needed that sound path with damping in it to control the sound transmission.”
The grand staircase connecting The Loupe to the 520-foot upper observation level posed a special challenge. Flat surfaces could have turned that stairwell opening into an echo chamber. Fortunately, the design included a slotted-wood wall alongside the staircase, and that helped absorb the sound.
In the end, the renovation team was able to keep the noise down. “Essentially we hit our targets for mechanical noise control,” Bruck said.
In most of the Space Needle’s public spaces, sound tests indicated that the decibel level was in the mid-40s, which is about how loud it gets on a neighborhood street at night. “It was elevated in front of the food concession area because there’s refrigeration equipment and all that kind of activity,” Bruck said.
So if you’re looking for a quiet place to meditate on Seattle and its surroundings from on high, don’t stand in front of the food counter. (You probably didn’t need an acoustics engineer, or a journalist, to figure that out.)
Now that the renovation project is complete, Bruck can enjoy the Space Needle and its acoustically optimized glass floor purely as an observer. But other visitors can’t help running their own tests.
“On my visits up there, I’ve seen that the automatic instinct, it seems, for young boys is to stomp on the floor to see if they can break it,” he said. “Fortunately, they can’t.”
The Acoustical Society of America’s 181st meeting continues this week at the Hyatt Regency Seattle.