New Sound Dampening System at Ashmont

One factor may have been the original all rubber suspension as I read it was only good for smooth track and tended to be very bouncy on rough track. One European system even claimed riders got seasick with the all rubber suspension. Adding the metal coil springs and extra vertical shock absorbers may have made a better controlled ride.

The sound issue at Ashmont loop is back:

Dorchester Reporter - T lays out plans to mute screeching Ashmont trolleys

The MBTA is pushing ahead with a multi-pronged approach to lower the volume of the screeching wheels at Ashmont Station as local residents say they are running out of patience.

In a meeting at All Saints Church last week, area residents, plagued for years by the high-pitched squealing produced by Mattapan Line trolley cars making their way around the bend at the T station, met with top brass from the MBTA and local elected officials where the MBTA laid out the three solutions they’re pursuing: rubber hubs for the wheels, a spray that would coat the front wheel with a liquid, and a “tune vibration absorber” on the wheels.

The rubber hubs are already in place on the nine-car fleet, but some residents, who say the noise is hurting property values and causing emotional and physical pain, assert they can’t hear a difference. One of them, Brian Driscoll, noted that there had been an improvement, but he added, “It’s still very loud.”

Jeffrey Gonneville, the MBTA’s chief mechanical officer, said he sympathized. “It really is unbearable,” he acknowledged.

Click on the link to read the rest.

Has anybody sued whoever designed the new loop for being idiots and not accounting for this?

The old loop didnt have problems this severe at all.

Or are contractors not liable for bad design in this state?

I wonder if putting down ballast to the level of the railhead would dampen the noise?

Most of that is hyped b.s. Residents don't notice it after having lived there for a while. Who it's hurting are the yuppies who have moved from the suburbs of Cincinatti or Wellesley and want the diversification and city life of Dorchester but don't want the sounds that go with it. Complainers either purchased impulsively without evaluating first, or are trying to sell and can't get the high prices that the rest of the city is getting from those yuppies that checked it out before buying.
"Well Buffy, this is appalling. Wellesley Hills never sounded like this. Let me text Mr. Davey, so that this may be squelched !"

3rdrail wrote:Most of that is hyped b.s. Residents don't notice it after having lived there for a while. Who it's hurting are the yuppies who have moved from the suburbs of Cincinatti or Wellesley and want the diversification and city life of Dorchester but don't want the sounds that go with it. Complainers either purchased impulsively without evaluating first, or are trying to sell and can't get the high prices that the rest of the city is getting from those yuppies that checked it out before buying.
"Well Buffy, this is appalling. Wellesley Hills never sounded like this. Let me text Mr. Davey, so that this may be squelched !"

No, the sound level went up with the new loop, because it's much tighter.

The T wouldnt be spending so much money on this if it wasnt the case, but theyve down sound tests and the db level is dangerous.

jamesinclair wrote:No, the sound level went up with the new loop, because it's much tighter.

Can I see your documentation for that, please ?

jamessinclair wrote:The T wouldnt be spending so much money on this if it wasnt the case, but theyve down sound tests and the db level is dangerous.

Can I see your documentation for this also, regarding the "dangerous" noise level test(s) please ? The documentation that I have found disputes your claim, indicating that the noise level at the center of the new Ashmont Loop after mitigation (noise dampening) was 75 dBA, reduced by 23 dBA, measured on 9/11/09. Source - MBTA/Harris Miller Miller & Hanson Inc. http://www.mbta.com/uploadedfiles/About ... y%2020.pdf

As this report indicates, 75 dBA is about the same noise as an air compressor at 50' and less than a diesel truck at 50'. A food blender is about 85 dBA at 3', and normal speech is about 60-65 dBA at 3'.

James, I'm sure that judging by the tone of your definitive denials of my claims that you must be relying on a solid foundation, and I'm eager to see it.

Also, if the sound levels were dangerous for people tucked away in there homes hundreds of feet away, what would it do to those standing on the platform, riding the car, or especially the operators who turn that loop all day long?

Aside from all the numerical evidence supplied, the major thing that sticks in my head regarding this study is that the Harris Miller Miller & Hanson Inc. measurements found that the noise level caused by PCC's at the center of the Loop - was less than that of a diesel truck. Would that not suggest that a diesel bus is louder as well ? Aren't diesel buses to be found, not only in exterior, but interior stations (rhetorical question) where the noise would be reflected off walls and therefore exacerbated ? If nothing else, doesn't this fact alone indicate that these complaints about the Ashmont Loop are nothing but Yuppie Nimby hooey ?

3rdrail wrote: Can I see your documentation for this also, regarding the "dangerous" noise level test(s) please ? The documentation that I have found disputes your claim, indicating that the noise level at the center of the new Ashmont Loop after mitigation (noise dampening) was 75 dBA, reduced by 23 dBA, measured on 9/11/09. Source - MBTA/Harris Miller Miller & Hanson Inc. http://www.mbta.com/uploadedfiles/About ... y%2020.pdf

As this report indicates, 75 dBA is about the same noise as an air compressor at 50' and less than a diesel truck at 50'. A food blender is about 85 dBA at 3', and normal speech is about 60-65 dBA at 3'.

James, I'm sure that judging by the tone of your definitive denials of my claims that you must be relying on a solid foundation, and I'm eager to see it.

The documentation is the study that went into that presentation. It doesn't seem to be available on the MBTA website any longer.

Highest db was 99! And this was for almost 30 seconds at a time.

Remember, decibels are a log scale, not a linear one.

Also note the frequency. A diesel truck may be loud, but it's a low rumbling. Train wheels = very high pitch = very, very annoying.

As I said above, all this "noise mitigation" effort must be payed for by the people who designed and built the new, tighter loop, not the MBTA. They screwed it up.

So you're telling us that your documentation was available yesterday publicly, but isn't now ?

Honestly, with all due respect, I'm beginning to wonder. We've gone from "dangerous" to "very, very annoying". Maybe it's not the noise that's very, very annoying.

jamesinclair wrote:

3rdrail wrote: Can I see your documentation for this also, regarding the "dangerous" noise level test(s) please ? The documentation that I have found disputes your claim, indicating that the noise level at the center of the new Ashmont Loop after mitigation (noise dampening) was 75 dBA, reduced by 23 dBA, measured on 9/11/09. Source - MBTA/Harris Miller Miller & Hanson Inc. http://www.mbta.com/uploadedfiles/About ... y%2020.pdf

As this report indicates, 75 dBA is about the same noise as an air compressor at 50' and less than a diesel truck at 50'. A food blender is about 85 dBA at 3', and normal speech is about 60-65 dBA at 3'.

James, I'm sure that judging by the tone of your definitive denials of my claims that you must be relying on a solid foundation, and I'm eager to see it.

The documentation is the study that went into that presentation. It doesn't seem to be available on the MBTA website any longer.

Highest db was 99! And this was for almost 30 seconds at a time.

Remember, decibels are a log scale, not a linear one.

Also note the frequency. A diesel truck may be loud, but it's a low rumbling. Train wheels = very high pitch = very, very annoying.

As I said above, all this "noise mitigation" effort must be payed for by the people who designed and built the new, tighter loop, not the MBTA. They screwed it up.

I just clicked the link, the PDF loaded just fine for me.

http://www.mbta.com/uploadedfiles/About ... y%2020.pdf

It says they had an average of a 17 Db reduction, which isn't bad.

I was out there a few days ago, and I did notice that the PCCs are a LOT quieter going around the loop now then they were before. (I've had reason to visit the line every few weeks since Septermber - so I've been listening to it pretty regularly.)


I also agree that the screeching of the wheels is a particularly annoying sound to listen to. I live about 100 feet from a Green Line crossover, so I can hear and feel the thud of trains hitting that switch every 5-10 minutes, all day, every day. I don't notice or pay attention to it that much anymore, but there's a big difference between that rumble and the squeal of a train being short-turned, even just going over that one switch - the screeching is more then enough to be irritating and get my attention.

Edit: wow, this turned a lot longer than I expected. In short: the squeal is high-frequency noise, which has to be considered carefully.

What piques my interest here is the frequency spectrum on the last page of the report. Massive peak at 4.1 kHz (equal in pitch to the second-highest key on the piano), and harmonics at 8.2, 12.3, 16.4, 20.5, and 24.6 kHz. Those are high frequencies, much higher than almost anything you encounter in everyday life (unless, of course, you change at Park Street).

High frequencies are a completely different realm from the low-frequency rumble of a bus or a locomotive. They carry farther, and they are perceived to be stronger than lower noises. My school's marching band has one piccolo player. She's not any louder than the rest of us, but she can quite literally drown out a 6-person band (including a dozen trumpet and four base drums) because the human ear is so sensitive to her notes - which are right up around 4 kHz.

Those frequencies are also dangerous. They damage your hearing much more easily than low frequencies, and they cause headaches. The piccolo player wears earplugs when she is playing high passages, and I feel that the noise at Boylston or Park Street (which are Green Line trolleys, yes, but the screech is fundamentally the same) is far greater than standing an equivalent distance from her. If you can hear that piccolo - loudly - across a football field, then you can certainly hear the trolleys.

One part about what you're saying I absolutely agree with - that it's yuppies complaining. But I disagree that it's just them being selfish. Starting around age twenty, the upper frequency of hearing drops from over 20 kHz to only about 12 kHz by late adulthood. You're about fourty, I'm guessing, Mr. Joyce. You probably can't hear that 20 kHz peak any more, and the 16 kHz peak is getting fainter - and none of that is your fault. it's just life.

Noise-induced hearing loss - which can result from a lot of causes, including the noise of a city - causes a "notch" in hearing at between 3 and 4 kHz (source). Between losing the upper harmonics and losing that notch, a longtime city resident is not going to physically hear much of the squeal, and what they hear will be cleaner - and easier for the brain to filter out - because there's less harmonics. I know that I hear the Green Line squeals better than most riders, and the key variable seems to be age.

I have not personally had a chance to visit Ashmont (this fall...), and I certainly don't live there. I can't know for sure how disruptive the noise really is or isn't, and it might well be a couple of NIMBYs with a chip on their shoulder. But that high-frequency sound does worry me, and I can see where the complaints could come from.

(Almost done...)

Course, the MBTA shoulda had a brass player on their little team of audio experts... they woulda recommended Al Cass valve oil. If there's anything that can cure the sounds of sliding metal better, then I've never seen it.

Yeah, ...ummm that's about right. Yeah, I'm about 40.

The million dollar question persists (not my age). Aside from being annoying (and noticeable if you happen to be evaluating a neighborhood that you are thinking of buying in), is the sound dangerous (according to an audio specialist). Is it capable of breaking an egg ? (Cosmo- take note.)

Agreed, and whether it goes beyond annoying into dangerous is beyond my knowledge.

And what about an egg...?