An estimated 5.2 million young Americans have some degree of hearing loss from sources like rock concerts, fireworks and lawn mowers, government research suggests.
Average weekday ridership 8,505,966 as of December 31, 2007.
Underground stations 277
Elevated Stations 153
http://www.nytimes.com/2006/10/17/health/17nois.html On subway platforms, the mean maximum noise level was 94 decibels. The highest level, 106 decibels, was recorded in Union Square station, and 12 percent of all platforms in the system exceeded 100 decibels. The maximum safe exposure duration at 85 decibels is 45 minutes, according to the E.P.A.; above 105, it is 30 seconds.
Can I connect this information?
It seems we are losing our hearing by way of many sources. The subway proves to be a major contribution, as well as other sporadic interactions, to equipment on the streets, passing by construction sites etc.
While looking for statistical information I read that subway commuters are combating the noise levels in the station and on the train with their own in ear music/headphones/mp3 players.
This also proves damaging. The best thing to do is where ear plugs, some sort of hearing protection. And if you must listen to music, Noise cancellation head phones are readily accessible to purchase.