FAA Human Factors Design Standards (Exerpted for your amusement)

(Remember, these standards only apply to FAA facilities)

13.5.2.3 General noise levels. Workplace noise shall be maintained
at levels that will not (1) interfere with necessary voice, telephone,
and radio communication, (2) cause fatigue or injury, or (3)
degrade overall system effectiveness.

13.5.2.7 Operational areas. Ambient noise in areas requiring
frequent phone use or requiring occasional speech communication
(for example, operations centers, control rooms, tower cabs, and
dynamic simulation rooms) at distances up to 4.6 m (15 ft) shall
not exceed 55 dB(A) or 47 dB PSIL-4; shop offices and
laboratories shall not exceed 48 dB PSIL-4.

13.5.2.8 Equipment areas. Ambient noise in areas requiring
frequent telephone use or frequent speech communication (for
example, computer rooms, engineering areas, equipment rooms,
and telephone switching centers) at distances up to 1.5 m (5 ft)
shall not exceed 65 dB(A) or 57 dB PSIL-4.

13.5.2.9 High noise, remote areas. High noise, remote areas that
are normally unmanned shall not exceed 85 dB(A).

13.5.2.10 Occupational noise exposure and control.
Administrative or engineering controls shall be used to reduce the
sound levels to within permissible noise exposure levels listed in
exhibit 12.12.8. OSHA 29 CFR 1910.95 shall be used in determining
equivalent A-weighted sound levels for daily exposure. A hearing
conservation program shall be administered any time an employee's
noise exposure equals or exceeds an 8-hour time weighted average
of 85 db measure on the A scale (slow response) or equivalent
without regard to attenuation that may be provided by personal
protective equipment. OSHA 29 CFR 1910.95 shall govern the hearing
protection program.