Why Are BART Trains So Loud?

Sometimes the noise on BART is so loud you can hardly think. Why such a racket? Bay Curious is a new podcast from KQED that’s all about answering your questions about the Bay Area. Find us on iTunes, Google Play or NPR One.

KQED listener Eric Bauer wanted to know something most Bay Area BART passengers have probably wondered about at one point or another in their commute: Why are the trains so loud?

“They scream like banshees,” Eric said. “One should probably use hearing protection.”

First off, Eric, you’ll be happy to know there is a plan in the works to dampen BART’s signature wail.

The bad news is the fix is tied to the rollout of new BART train cars, which will begin late this year and won’t be done until 2021. So until then, you might want to keep some earplugs on hand.

Now, on to the business of what causes that banshee scream.

To find out why the trains are so loud, I took a trip to the BART maintenance shop in Hayward to meet Henry Kolesar, BART’s chief vehicle engineer. Not only does he know every little sound his train cars make, but he can imitate them startlingly well. The man has spent a lot of time in and around BART trains.

When I arrived, Kolesar was sitting at his desk behind a stack of engineering reports. The one on top was a sound test of the BART system done a few years ago. First off, Kolesar explained, the trains make all kinds of noises, and not all of them are unpleasant. Believe it or not, some of the sounds are actually music to an engineer’s ears.

BART makes three main sounds that passengers hear. There is a nasally electronic hum some of the trains make as they are braking. This is the sound of BART saving energy, Kolesar says. As some of the newer train cars brake, they convert mechanical energy into electric energy that can be used to run the BART trains. As they do this, the train cars make this kind of “nnneeoooowwww” sound.

The other two sounds fall squarely into the unpleasant category.

The first comes from wheels running on rails that have become worn and bumpy — “corrugated,” to use the technical term. When BART trains go over corrugated rail, they make a low-pitched, continuous “uuunnnhhh.” It sounds like some blend of a confused “uhhh” and the buzzer noise when someone answers incorrectly on one of those old daytime game shows from the ’80s.

BART actually has a big machine that grinds down the bumps on corrugated track, eliminating some of the noise. This explains why sometimes a portion of the BART system makes loud uuunnnhhh sounds one day and doesn’t make a peep the next. You aren’t crazy — they just smoothed out the track at night.

Finally, there is the infamous squealing banshee wail.

This happens when the trains go around turns, and it is most pronounced in tunnels, where the sound waves bounce back into the train and drill into passengers’ ears. Kolesar did not imitate this sound. It falls a wee bit out of his natural vocal range, he said. But KQED listeners were not afraid to give the banshee squeal a shot.

We asked listeners for their impressions of the sound, and we got some accurate and unexpected descriptions.

It was compared to a baby seal calling for its mom, a 10-year-old slowly releasing air from a balloon at a birthday party, the high-pitched, long-lasting “goal scream” of a soccer commentator, the soundtrack from the trippy, space/time travel scene in 2001: A Space Odyssey (which, at times, is eerily spot on), and my personal favorite: all of the happy emojis that ever existed, put in a blender, desperately crying for help.

You can hear a little montage below of what KQED listeners think the BART wail sounds like. Thanks to everyone out there who contributed, and to Meghan Mund and Lucas Waldron for recording their ear-splitting BART squeals.

Now hold on a minute. Kolesar does not agree with the categorization of BART as loud. He says BART is rather quiet — that is, if you consider how fast it goes.

“People say BART cars are loud, but it’s all relative,” Kolesar says. BART averages 35 mph, which is much faster than trains in most cities. New York’s subway goes about half as fast on average — 17 mph. And as anyone who has taken the A train can tell you, New York subway cars are not known to be silent types.

Also, Kolesar says BART’s banshee wail is not a mistake. It isn’t the result of some design mishap. It came from a conscious engineering choice.

Engineers had to make a trade-off back when they started building BART more than 50 years ago. They decided to make the wheels solid axle — or connected — so that they rotate at the same rate. Kolesar says that makes the trains quiet on the straightaways, which constitute a majority of BART’s tracks. But because of the design, one of the wheels ends up getting dragged against the rail on turns, which causes that high-pitched squeal.

“So one wheel has to be sliding while the other is rolling,” Kolesar says. “Or they both have to be slightly sliding, because they are turning at different speeds going around that bend. It just makes noise.”

Now there is a plan to make BART quieter. New train cars will have tapered wheels that drag less on the rail. That will help a little. But there’s a bigger change coming with the new cars.

Kolesar says the “the doors are the key.” No matter what you do, the wheels will always squeal a little. The current doors let in lots of that sound, but the new trains will have better insulated doors that could make the trains two or three times as quiet.

Again, we’ve got to wait a few years to enjoy that kind of relative quiet. All the old squealing cars won’t be replaced until around 2021.

After then, should you grow nostalgic for the BART wail, you could always hear an approximation by watching 2001: A Space Odyssey.

But for right now, commuters like Eric will have to endure the BART wail, or as I like to think about it: happy emojis going into the old blender.

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