Hearing Dangers on Mass Transit

Well, it depends upon the exposure. 'Some noise for a long time' and 'a lot of noise for a short time' are roughly equivalent, and one would hope that acoustic conditions within better-designed rolling stock would be good.

There are already occupational exposure guidelines on noise and legislation to protect employees in most countries, so the approach must be to look at employees' exposures under the legislation, as the employees have the longer exposure times. The riders will get the benefit from the protection given to the employees.

In all cases removing the source of the noise must be seen as the first priority.

Among the more prominent sources:

• wheel/rail grinding can be solved by adding flange lubrication
• motor noise can be reduced by better construction and maintenance
• auxiliary equipment noise (air compressors, for example) can be reduced by better construction and maintenance
• wheel/rail interaction noise can be reduced by moving towards continuous rail rather than fishplate-jointed rail.
• etc., etc.

All of what you have said is good in theory.

BUT! our government has rarely acted in the interest of the Public - I once overheard a rail manager say "If it wasn't for those bloody customers we could run a perfect system".

Guess he does not know that those same "bloody customers" pay his salary!

They know. They are being monitored. Wheel screech is the biggest problem and you can't make it all go away since rail shunting requires a certain amount of friction to keep the wheel-to-rail electrical contact clean.

Interesting post - I take the train into work every day and have noted how loud it can get in the city station, so I'm interested to see if I would be at risk. Okay then, lets figure this out.

First of all, I'm going to make some broad, sweeping assumptions

1. My train ride into work is an hour long each way, so I'm going to assume this is our worst case scenario :P
2. The damage that noise can inflict upon your hearing is dependant on the frequencies at which the noise occurs, so in the interests of consistancy I'm going to assume that the all the sound levels quoted are 'A-weighted' (a scale that weights acoustic levels reciprocally to the human ear's frequency response to provide sound level measurements of equal aural sensitivity across audible frequencies).
3. During the journey, sound levels are continuous at 80 dB(A).
4. I'll wait on the platform for no longer than 20 mins a day, where I'll assume its 102 dB (worst case) continuously
5. I work in a fairly quiet office which should have an average sound level of 40 dB(A) (thats an Australian design guide-line for the upper limit of continuous office noise)
6. I work for 8 hours a day.
7. Sleeping time / time at home is for the rest of the day, (assuming i don't go out ...) and is around 30 dB(A)

To calculate the average daily noise level:

La = 10*log{10}*1/24*( t1*10^(La1/10) + t2*10^(La2/10) + ...)

La = daily average sound level total in dB(A)

La1 = sound level of time interval t1

let:

t1 = time on station (1/3 hours) - La1 = 102 dB(A)

t2 = time on train (2 hours) - La2 = 80 dB(A)

t3 = time at work (8 hours) - La3 = 40 dB(A)

t4 = time at home (13 + 2/3 hours) - La4 = 30 dB(A)

Therefore, La = (drumroll please...) ... 83.6 dB(A) !

Thats well above the WHO's reccomendation. While I assumed the train and station noise levels to be worst case, the fact that I work in an office compensates for that. If, for example, I was commuting on the train to get to a factory or machine-shop workplace, I could expect 85 - 90 dB(A) during my working hours - which would make the equation a lot worse. In regards to the question - "should a government agency monitor these levels?"... its my experience that such government agencies, or 'watchdogs' don't do anything useful, nor are they given the power to implement any change. In my opinion; train commuters in NYC should definately be advised of these health risks and be provided with information on how to minimise those risks.

I travel with sound cancelling headphones - you should get a pair - they're awesome!

Regards,

TinTin

Very good example of daily cumulative noise exposure.

Do you walk or drive to the train station ?

While "at home" do you have noisey vehicles on the streets ?

I had people suggest the noise cancelling headphones, I think there should be a caveat that they only be used by people who are awake.

I drive to the station, takes me about 8 minutes. My house is in a fairly rural area, so there's hardly any traffic noise. In my last post, I forgot to factor in the weekend days though, where I don't commute on the train or go into work - that would take my weekly average down, but it'd still be above 70 dB. I'm not sure how effective my noise cancelling headphones are - they're designed to cancel out noise around 300 Hz very effectively, which seems to work better on planes.

Regards,

TinTin

Don't know how you calculated that, but it comes out to 47.7 dBA for the time weighted average.

Did you use this formula? :

La = 10*log{10} (1/24*( t1*10^(La1/10) + t2*10^(La2/10) + ...) )

Its from my old acoustic engineering lecture notes. I've triple checked it and still get the same answers. Sure you're using a base 10 logarithm? How did you arrive at your answer? If you just consider the 102 dB sound for 0.333 hours, and assume that all other noise for the rest of the day is 0dB,

La = 10* log ((1/24)*0.333*10^(102/10)) = 83.3 dB(A) - so it can't be lower than this figure.

I'm not familiar with what you used. I'm used to the OSHA calculation. I'll have to look further. Does WHO use your formula?

See my mistake. Back at you later.

Yeah. Got 80.9 dBA. Too loud for me, but OSHA thinks it's OK.

Yeah, too loud for me too! I remember from one of my lectures that the acoustic safety regulations (at least in Australian work places, equivalent to 85dB (A) limit over 8 hours) were based on an expected 25% hearing loss at common speech frequencies over something like 20-25 years - its a little worrying

Oh crap! I think that's why I got a different number - 8 hours. I'll work on this when I get a chance. In the meantime, don't mind me. I love to argue but freely admit when my eyes start turning brown.

Haha, thats fine - I seem to make my fair share of mistakes - I'm sure you'll notice them on CR4 from time to time!

I've been out of work for 6 or 7 months. Wore hearing protection whenever possible around jets or carpentry tools. Intensity of ear ringing has diminished, but going broke. Don't hear ringing so much, but some extreme joint pain.

I had this thought some time ago when i started to take the train to uni/work...I saw a person wearing hearing aids and thought about it's technology. When i looked into it, I found that the newer digital hearing aids have noise cancellation while only amplifying the speech band...I then thought of a great idea...Use a hearing aid...the ear mold blocks all sound...have the hearing aids only amplify to normal hearing level...and I do use them for traveling the railways and any loud situation. They take getting use to, but are really effective. The down side is is that people think i'm hearing impaired when actually i don't really need them at all.

Hell no! Anyone stupid enough to not wear earplugs when sound is obviously so noisy that hearing could be damaged should go deaf. There is too much big brother already. It would be nice if loud noise could also make the stupid become mute! We would have far fewer politicians.

Lastly, many subway passengers are blasting music players into headphones at volumes far greater than whatever noise the subway makes. Are we now going to legislate headphone volumes? Let the W.H.O monitor something more important like the rate that the USA is deterioriating because of too much monitoring by politicians!