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NYC BUILDING CODE 27-770: Noise control of mechanical equipment.

(a) Minimum airborne noise insulation requirements.

(2) MECHANICAL EQUIPMENT SPACES.

a. Ventilating openings into mechanical equipment
spaces. -Ventilating openings into boiler rooms and
other mechanical equipment spaces shall not be located
in yards or courts where there are windows opening
from living quarters, unless such ventilating openings
are provided with sound attenuating devices if needed
to limit noise transmission to NC-40 (noise criterion)
levels in the exposed dwelling units. For permits issued
after January first, nineteen hundred seventy-two, the
permissible noise levels shall not exceed NC-35.