But a 2006 Columbia University study measured sound generated by New York subway trains and found that the average maximum noise on subway platforms stood at 94 decibels (the decibel, or dB, being the preferred unit of noise measurement), with peaks of over 100. This is well over the volume of a fully revved-up chain saw held at arm’s length. Moreover, the CU study found, merely spending a half hour in the subway system, exposed to the average noise level of trains, would exceed safety guidelines recommended by the Environmental Protection Agency and the World Health Organization, potentially resulting in damage to one’s hearing.

George Michelsen Foy, Zero Decibels, loc. 39