The 'acceptable' noise level is:

(85 dB): Ref: (648-Park 20th)* "A daily exposure up to 85 dB is about the limit people can tolerate without substantial damage to their hearing"* Auditory fatigue - appears in the 90 dB region and greatest at 4000 Hz* Deafness - Most temporary hearing loss occurs in frequency range between 4,000 to 6,000 Hz* Repeated or continuous exposure to noise around 100 decibels may result in permanent hearing loss* Exposure to noise above 160dB may rupture the tympanic membrane and cause permanent loss of hearing* Most disturbances to speech communication lies in the 300 - 500 Hz range.