How loud is too loud? Exposure and Decibels [dB].

Standards set by OSHA (Occupational Safety and Health Administration) indicate that continued exposure of unprotected ears to noise over 85 dBs will cause a gradual hearing loss in a significant number of individuals.
Louder noises will accelerate this damage. The allowed exposure time decreases by ONE HALF for each 5 dB increase in the average noise level.

Both the amount of noise and the length of time you are exposed to it determine its potential to damage your hearing.

Noise levels are measured in decibels (dB). The higher the decibel level, the louder the noise.