Everything about a New York subway station is unpleasant. The grime. The rats. The overwhelming stench of it all. Then there’s the noise. Curved tile walls amplify every footfall and shout, not to mention the indecipherable blare of the PA. Eventually a train rumbles through at 94 decibels or more, announced by the whine of a motor, the screech of brakes, and the clack of wheels on steel.

Unfortunately, that’s the inevitable nature of a subway system, which must be robust. “The necessary architecture of a subway has to be incredibly strong, graffiti-proof, soot-resistant, human bodily waste-resistant,” says Alex Case, an architectural acoustician with the University of Massachusetts Lowell. The problem is, that creates something of an echo chamber where, “acoustically, what happens in the subway station stays in the subway station.”

Venture into the innocuous offices of the engineering firm Arup in downtown Manhattan, though, and you’ll hear the quiet—well, quieter—future of the subway. Or, at least, the future of the Second Avenue line.

The line’s first phase, a 4.2 mile stretch of track buried 10 stories below the Upper East Side, opens in December. When the entire line eventually opens, it will stretch 8.5 miles and include 16 new stations. The Metropolitan Transportation Authority has hired Arup to make them easier on the ears.

Arup’s acousticians can’t set up shop in a subway station, so they built digital models of the Second Avenue subway using recorded sounds and measurements, some collected from existing stations. They’d use these models to make subtle changes to a station design, exploring the best way to minimize the din.

MTA officials would experience these models in Arup’s SoundLab, a small, fabric-enclosed space with enormous curved screens and a bone-shaking sound system. Engineers fire sounds through 50 loudspeakers and eight subwoofers into this virtual sonic space, simulating the commuter experience. Sophisticated tools let them create acoustical renderings and manipulate them to bring spaces that haven’t even been built straight into your ear canals.

The Din

In the SoundLab, an acoustician pulls up a file depicting what the subway might sound like if it were just another station in New York. It’s a a cacophony, with the announcer’s voice vague and dispersed. All you can think is The what train is coming? “Local track” who?

Incomprehensible announcements aren’t just annoying and unhelpful, they’re potentially dangerous. The system that alerts passengers to arriving and delayed trains also tells them what to do in an emergency.

Fighting the Din?

In an ideal world, the MTA could envelop tracks in fabric or foam, muffling the sound of its machinery, its riders, its everything. But imagine how filthy that would get (San Francisco BART riders know all about that). The MTA has to work within its existing infrastructure, its regular power-washing schedule, and its tight budget.

Arup’s plan to rethink the subway begins—where else?—with the track. The MTA is investing in a “low-vibration track” using ties encased in concrete-covered rubber and neoprene pads. It nixed joints between tracks in favor of a continuously welded rail that does away with the “badump, badump” of the wheels. That’s just the start.

“The big change is really in the finishes,” says Joe Solway, Arup’s acoustic lead on the Second Avenue subway project. Most subway stations are built with tile and stone, which bounce sound all over the place. MTA will line the ceilings with relatively absorbent rigid fiberglass or mineral wool—hardier versions of the pink, fluffy insulation in your attic—covered with a perforated metal or enamel sheet to keep it out of human hands. It’s like a Roach Motel for noise.

The ceiling will gently curve like others in New York, but it will direct sound toward the train instead the platform. The speakers, the safety raison d’être of the whole subway silencing enterprise, will sit at 15-foot intervals, angled to holler directly at riders, says Solway, for ideal resonance and volume. Improved cables, sound-isolated booths, and greater diction by those making announcements will further improve fidelity.

Arup’s engineers won’t specifically quantify the noise reduction, but say the Second Avenue line will be a “more acoustically appealing environment.” An acoustician presses another key on the computer, and the subway comes alive again. This time, the announcement is crisp and clear. Not perfect, maybe, but better. Tolerable, even.

If only the MTA could engineer away the primary reason for so many of those announcements: delays.

Original post:  

Get Ready for Quieter NYC Subway Stations (Yes, It’s Possible)