Sound engineers become integral in building projects
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Companies love to include grand rooms in their buildings, cavernous statement spaces with high ceilings and monolithic glass walls that draw the eye and the mind upward. But for all their visual majesty, these symbols of ambition and collaboration often come with a serious drawback: terrible acoustics.
That's because the very features that appeal to our eyes — large, hard, flat surfaces — are the hardest on our ears, reflecting every sound and making those spaces uncomfortably noisy.
Sound-absorbing panels and other treatments have been used for decades to improve acoustics in large spaces. However, architects often worry they will spoil a building's clean look. It's also hard to appreciate how unpleasant an acoustically deficient room can be until you're standing inside it, shouting to be heard over the din.
This is where a company like Acentech Inc. can help. A Cambridge acoustics consulting firm that was once part of the famed tech pioneer BBN Technologies, Acentech uses sophisticated computer-generated audio simulations called "auralizations" that make it possible to hear a building before workers ever break ground.
"Auralization is acoustic rendering," said Matthew Azevedo, an Acentech engineer. "An architect would never tell a developer 'Here's the floor plan, just imagine what it's going to look like.' Well, we feel the same about acoustics."
Acentech recently used auralization to help solve a tricky problem: making the massive, four-story atrium of TripAdvisor's new headquarters in Needham sound good.
TripAdvisor and its architectural team wanted the atrium to work acoustically in a variety of scenarios, so that employees could talk comfortably over lunch on the ground floor, or lean over the third-floor balcony and hear the chief executive give an all-hands speech without straining. But TripAdvisor didn't want to meddle much with the atrium's epic look and feel, with its multiple flat, sound-reflecting surfaces, including a ceiling painted to look like the sky and a towering wall of windows.
"Architects love these big, open spaces with lots of glass and exposed steel and all these wonderful hard surfaces," Azevedo said. "Our job is to make it behave acoustically like a theater."
To build a digital model of the atrium, Azevedo and his colleagues fed recorded sounds — passing traffic, workers chatting over lunch, a manager giving a presentation — into acoustic modeling software loaded with a 3-D blueprint of the TripAdvisor atrium. Each surface was assigned the acoustical properties of its construction material: windows of a certain thickness, carpets that soak up certain frequencies, and so on.
The resulting simulation is best experienced in a specially designed room at Acentech that bristles with surround-sound speakers. Here, with a few mouse clicks, engineers can hear the different recorded sounds from any vantage point: a speech during rush hour, for example, heard from the back row of the atrium, with the air conditioning on.
Acentech can also simulate additional acoustic treatments. Installing sound-absorbing panels, for example, noticeably cut down the sound reflections from a speaker's voice, making it far easier to hear, even from the farthest corners of the atrium.
TripAdvisor ultimately took a number of Acentech's recommendations, installing more carpet, hanging "clouds" made of absorptive fiber from the main ceiling, putting sound-absorbing fiberglass behind other ceiling areas, and adding fabric panels and perforated metal to break up large, sound-reflecting surfaces. The result is an atrium that's grand in scale but surprisingly friendly to the ears.
"It's both aesthetically beautiful and acoustically functional," said Matt Gabree, TripAdvisor's director of global office experience.
"We can serve 800 people lunch every day without creating too much of a roar, and it can seamlessly transition into a forum where I could talk to 70 people without it sounding like I'm in a huge cave."
Modern acoustic design dates back to at least the 1890s, when Wallace Clement Sabine, a young physics professor at Harvard University, was asked to improve the audibility of lectures at the school's Fogg Museum.
Sabine quickly realized that the key to a room's sound was the amount of time a sound reverberated — too short, and a space sounded unpleasantly "dry"; too long, and the sea of overlapping reflections made it difficult to distinguish words.
But rugs, cushions, and even human bodies soaked up sound, he found, meaning that it was possible to improve the hall's acoustical properties by adding absorptive materials.
The project's success won Sabine a job as the acoustical architect for Symphony Hall in Boston, which is still widely considered to be one of the best-sounding venues for classical music. Today, he's celebrated as the father of modern acoustic design.
The field has advanced by light years since then, thanks mostly to computers. Audio simulations, once used mostly for concert halls and sound-sensitive buildings, can now be used for many types of construction projects.
The developer of a new apartment building next to a subway line, for example, could use the technology to determine which units need thicker windows to block out the noise from trains.
"Now [the developer is] empowered to know what they're up against," said Chris Savereid, a recently retired Acentech engineer who led the project at TripAdvisor.
"And if they think they rent that apartment right next to the train tracks with standard windows, more power to them."