The SoundLab, Arup

If you are a cool person who knows about architecture and design, you probably know all about Arup. As for me, I only recently heard about what is easily the world’s hippest engineering consultancy. But even I was already unwittingly familiar with Arup’s work, as it is behind several of the most iconic structures built for the Beijing Olympics, the new Lincoln Center, the Seattle Central Library, a few particle accelerators, and even the latest skyscraper being built down the street from my old apartment in Mexico City—just to name a few of its many projects.

Less tangible but no less impressive is the work of Arup Acoustics, which, broadly speaking, helps clients build spaces that are conducive to listening to certain sounds and not others. Despite its impressive list of projects ranging from wind farms to opera houses, the crowning achievement of Arup Acoustics may be eight sparse rooms scattered across the world: the SoundLabs.

The SoundLab in Los Angeles. Photo courtesy of Arup.

Due to its black walls, low lighting, and intense sound-proofing, the LA SoundLab is an aggressively peaceful room. The layout seems simple enough: twelve speakers are arranged along the surface of an imaginary sphere that completely surrounds the chairs pictured above, and four subwoofers are strategically positioned on the floor. But to understand what was so special about the SoundLab, according to my tour guides Nick Antonio and Matt Wilkinson, I needed to understand a little about the different ways we record and listen to sound.

When we experience sound in real life, it always has a spatial component—i.e., different sounds come from different directions. But that is a difficult effect to recreate when we play back a recording, even as our technology has advanced from mono to stereo to surround sound. The SoundLab goes well beyond even the most advanced movie theaters in that it is an ambisonic space. When all twelve of its speakers are in use, you are surrounded by a complete sphere of sound, with each piece of that sound coming at you from a different direction. The effect, as Nick said, was to take the sound from “2-D to 3-D.”

This spatial component is what makes the SoundLab more than just a really good set of speakers. When I listen to music at home, no matter how advanced my sound system might be, I can only specify the piece I want to hear and the group I want to hear play it. The SoundLab lets me add the space in which I want to hear it played. That’s right: the SoundLab can play a space.

What a space sounds like depends on many variables, including but not limited to the positions of the sound’s source and its receiver, the size of the room, the material used in its construction, how many seats (and people) are in it, and even the shape of the decorations on the walls. All of these elements affect how the sound reverberates in a space, how it decays, and how much of it is absorbed—i.e., which sounds come at you from which directions and at what times. Because the SoundLab takes into account the directivity of sound, it can accurately reproduce the unique acoustics of any other space. Nick didn’t mince words about what an accomplishment this is, saying that the SoundLab is “the next step in the way that acoustics is recorded and, more importantly, listened to. Because we’ve got all that spatial information.”

In order to play a space in the SoundLab, you first need to know what that space sounds like. To that end, members of the Arup Acoustics team have travelled to concert halls all over the world to measure their impulse response functions—what Nick called their acoustic “fingerprints.” By playing a sharp click in a space (the impulse) and using a state-of-the-art soundfield microphone to record and measure how the different frequencies in that click travel around the room (the response), the engineers can derive the acoustic properties of the space (its unique impulse response function) and program them into the SoundLab.

The Großer Musikvereinssaal in Vienna is one of the many spaces you can listen to in the SoundLab. It is widely regarded as having some of the best acoustics in the world. Photo courtesy of the Musikverein.

Back at the SoundLab, the Arup acousticians take a recording done in an anechoic chamber, or a space where sound doesn’t echo, and play it into the impulse response function of a particular space. (A recording done in an anechoic chamber is like an acoustic blank slate–you hear the sound emanating from its original source and nothing else.) So by playing the same anechoic recording into the various impulse response functions available in the SoundLab, you can do a side-by-side comparison of the acoustics of spaces that many be hundreds or thousands of miles apart from one another in the real world. During my visit, I used an iPad to toggle back and forth between the same piece of music being played in the Musikvereinssaal in Vienna, which is widely regarded to have some of the best acoustics of any concert hall in the world, and the old Northrop Auditorium in Minnesota, which had some of the worst. I’m a long way from a trained acoustician—the embarrassing truth is that I probably wouldn’t even have noticed the terrible acoustics if I had seen a concert at the old Northrop—but being able to switch back and forth between the spaces so quickly allowed me to easily hear how different they were and appreciate just how much good acoustics add to a performance.

A photo of a full house at the old Northrop. All those seats made for some horrendous acoustics. Photo courtesy of the University of Minnesota.

Arup is currently working with the University of Minnesota to improve the acoustics at Northrop. It is going to take some pretty major changes to get it to the level of the Musikvereinssaal—most notably, removing about half of the existing auditorium’s 4800 seats. Agreeing to halve the possible audience for every performance in order to improve the auditorium’s acoustics represents a big leap of faith for the client. And that, says Nick, “is where the SoundLab comes into its own so brilliantly. Because we can demonstrate this to these guys and say, look, this what you’re gonna get.”

So not only can the SoundLab play existing spaces, it can play spaces that aren’t built yet. Just a few tweaks of an architect’s computer model of a building can turn it into an acoustic model, which can be used to derive the hypothetical space’s impulse response function. So not only could I compare the acoustics of the Musikvereinsaal and the old Northrop Auditorium, but I could hear the same piece of music as it will sound when it is played in the new Northrop as well.

A sketch of the new Northrop, which is scheduled to open in 2013. Closing down the space and removing thousands of seats will bring its acoustics closer to the Musikvereinssaal ideal. Image courtesy of Arup and the architecture firm HGA.

Concert halls like the Musikvereinsaal and Northrop are what Nick called spaces for listening, “the sexy end of acoustics.” But Arup Acoustics also works on projects at the “opposite end of the spectrum”—spaces in which the main concern is simply hearing. Prime among them is the Second Avenue subway line currently under construction in New York City. Nick played me a sound I remember well—a garbled PA announcement about express trains being all but drowned out by the din of the station. Then he played me what the same announcement could sound like in a station designed by Arup Acoustics. It was crystal clear. For the sake of everyone who has ever missed an announcement about service changes and ended up on the wrong train, I hope the MTA takes them up on their recommendations.

In addition to working with architects, Arup Acoustics often collaborates with artists. They even created a sort of outdoor SoundLab for Stephen Vitiello’s piece “Smallest of Wings,” which was installed in London’s Broadgate Arena. When people stepped inside the dome pictured below, they were surrounded by the sounds of fluttering bird and (much to my chagrin) moth wings; it sounded like being in the rainforest in the middle of London. Arup also recently used 3-D recording and listening technology to recreate a Lou Reed concert at CSU Long Beach as Lou Reed originally heard it from his position on the stage.

The sound art installation Smallest of Wings on display in London's Broadgate Arena. The position of the speakers around the dome resembles the layout of the SoundLab. Photo courtesy of Networked Music Review.

Even when nothing is being played, being in the SoundLab is a unique experience. No sound leaks in from the outside and there is no background noise—even the air conditioning is “approximately inaudible,” a lovely phrase Nick used to describe sounds that are “lower than the threshold of human perception.” Sound produced inside the room hardly reverberates at all, because, Nick explained, “we don’t want to impose the acoustics of this space onto the acoustics of the space that we’re playing.” Because sounds hardly carry at all in the SoundLab, it was difficult to hear Matt talking from the back of the room when Nick and I were sitting in the chairs just a few feet away.

Matt and Nick both studied physics in England, but they are the first to admit that designing a concert hall isn’t just about the science of sound waves. He can engineer a space to meet all sorts of specifications, Nick said, “but it doesn’t make it a pleasant space to be in.” In fact, Matt said, “If it was pure science, then this [the SoundLab] wouldn’t be as helpful as it is.” The SoundLab allows them to go beyond calculations and models and even the examples set by the great halls of the past and tweak their plans based not on abstract predictions or established principles, but on the actual acoustic experience of being in a space.

Acousticians spend a lot of time listening and, as such, they are very good at it. Matt said that sometimes he will move to a new seat in the middle of a concert because it’s like hearing two performances for the price of one ticket. The flip side, however, is that he is easily distracted by bad acoustics, most notably in noisy restaurants. Nick, for his part, compared listening to wine tasting. “I think there’s a parallel to virtually any sensory sort of thing that we enjoy, where the more that you do it, the more that you get back from it,” he said. As an acoustician, “you can listen to a space and you can enjoy it for what it is, and compare it back to the last ones that you heard and know why it sounds like it does, and why it sounds good, and that’s quite nice….It’s an educated palate.” But at the end of the day, there is no right or wrong way to listen. The SoundLab doesn’t tell you what your opinion about the acoustics of a space should be. It simply invites you to take the time to form your own.

Many thanks to Nick Antonio and Matt Wilkinson for showing me the SoundLab, and to everyone else at Arup LA for letting me nose around their offices.

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