August 18, 2017
“Auralization,” the Technology That Lets You Listen to a Room Before It’s Built
Noise can cripple an environment, so acousticians are using immersive sound technology to more accurately predict and prevent a barrage of distractions.
In 2013, the Cambridge, Massachusetts–based consulting firm and sound specialist Acentech was presented with a big challenge. It had begun advising travel-industry tech client TripAdvisor on the construction of the company’s headquarters for hundreds of employees in Needham, outside Boston. The suburbs, in other words, where there aren’t many places nearby for those employees to grab lunch. So it was decided that everyone would be fed onsite in a giant, four-story atrium, which would double as an amphitheater for company-wide meetings. That decision presented a serious noise problem.
Compounding this clamor would be the highway that the space looked onto, I-95. A glass wall would be all that separated this atrium-slash-dining hall-slash-auditorium from the busiest interstate in the country. How to make all these factors palatable to the human ear, invisibly and on-budget?
Using a combination of software and a vast library of recordings, the Acentech team developed audio files that Baker Design Group, the architects of the 282,000-square-foot building, could use to predict the aural quality of the atrium ahead of construction. The designers were given audio renderings, or “auralizations,” of how different acoustic treatments might mitigate the racket from all the sound sources pouring into the space—I-95, the cafeteria’s kitchen, the atrium’s PA system, HVAC blowers, and hundreds of human voices.
Based on that predictive experience, designers made educated decisions about how to temper the glass wall and which acoustic materials to employ in the atrium’s side walls and ceiling. Today, 800 employees have lunch in the cavernous room on a daily basis, and no one complains about noise. They just sit, eat, and catch up, unaware of the amount of planning that went into developing that easy-going space. “So much of what we do is invisible, but it makes a huge difference,” says Acentech sound scientist Matt Azevedo.
Acentech, which creates auralizations in its 536-square-foot “3DListening” room, is one of a number of acoustic consulting and engineering companies who are experimenting with immersive sound experiences to help clients understand and resolve the noise challenges they face. The process is time-consuming and not particularly cheap, but as Acentech director of architectural acoustics Ben Markham notes, it is far more cost effective than trying to fix severe audio problems after a building has already opened. “It’s much easier to do it right the first time. Our job is to look at an architect’s first sketch of a recital hall, for example, and say, ‘The ceiling needs to be raised. Oh, and by the way, this building is right in the flight path of Logan airport.’”
Markham and Azevedo, who joke that they are terrible people to eat out with because they hear (and point out) every last bit of din in a restaurant, have advised architects on corporate complexes, high-tech labs, multifamily housing projects, civic spaces, and performing arts facilities. Like other acoustic consultants around the U.S., they can propose treatments based on their experience-refined instincts. But what their auralizations do is help convince clients to take their advice on matters that aren’t as simply conceptualized or conveyed as form or color—judging when noise becomes detrimental to a space.
Sound itself is a pressure wave. It moves through an elastic medium—air, water, concrete, our bodies—and as it passes, it creates vibrations. What humans “hear” are these vibrations within a 10-octave range, but we experience felt vibrations at lower frequencies, like when you sense the subway rumbling under a city sidewalk. That rumbling is acceptable for a pedestrian on the street, but it would be a nightmare for the owner of a luxury condo apartment two floors up. Often, buildings turn out to be too good at conducting sound.
Fortunately, there are also plenty of new building materials that mask annoying vibrations and emphasize pleasing ones. Every year, technology advances in acoustical plaster products, panels, micro-perforated veneers, glass treatments, and much more. So acousticians have better solutions to recommend today, if they can get visually oriented designers to close their eyes for a second and consider the sonic implications of their creations.
“I can’t tell you how many architects have come in and said ‘My hearing’s not very good,’” says Raj Patel, who leads the acoustic practice at international engineering firm Arup. “But as soon as they hear simple comparisons, they become acutely aware of the differences. If we can get everyone to elevate their thinking on this, we’ll end up with a much better world.”
Arup has perhaps the most robust auralization facilities in commercial practice, operating ten branded Soundlabs in four countries. Like Acentech, they have also begun using Oculus Rift headsets to accentuate the auralization experience, offering clients the chance to move around “inside” a rendered space and hear what it could sound like from different points therein.
Acousticians as a group seem to welcome challenges, and commercial projects aren’t the only application for the technologies they are pioneering. “It’s a hot research topic in academia right now,” says Maarten Hornikx, an associate professor of urban acoustics at Eindhoven University of Technology in the Netherlands. “People are just starting to realize that sounds take energy from us, and can cost years of our lives. They have a health impact. Auralizations are the perfect tool to begin translating the acoustic consequences.”
The Acentech team also promotes the link between health and hearing. Recently in Cambridge, it has been working with Frequency Therapeutics, a drug company that hopes to reverse the effects of hearing loss. Azevedo built a portable audio simulator that could help the scientists there experience what it was like to lose your hearing bit by bit.
“You can still hear everything but there’s less resolution,” he says, likening the experience to having fewer pixels in a high-resolution image. Now that he has auralizations to prove his point, he’s one step closer to dropping the analogies altogether. His clients will only have to hear it to believe it.
You can get a taste of the process by listening to these three sound files from one of Acentech’s most recent performing arts advisory projects, University Hall—designed by Wilson Architects— for the University of Massachusetts Boston:
1. It starts with a recording of a cellist playing J.S. Bach in an isolated, super-absorptive sound studio:
2. Here’s that same cello piece, but now in a simulated rendering of what the UMass recital hall would sound like with Acentech’s recommended acoustics plan:
3. And finally, here’s a recording made this summer of the same cellist playing the same Bach piece in the completed recital hall:
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