Architecture

Acoustic Noise Criteria Guide

NC (Noise Criteria) ratings define acceptable background noise levels for different room types. Use this reference to set acoustic targets for HVAC systems and sound isolation design.

NC Rating Perceptibility Scale

NC 20–25Very quiet. Whispered conversation audible. Concert halls, broadcast studios.

NC 25–35Quiet. Soft speech at 6 ft. Bedrooms, private offices, courtrooms.

NC 35–45Moderately noisy. Normal speech at 6 ft satisfactory. Open offices, classrooms.

NC 45–55Noisy. Raised voice needed. Busy restaurants, factory offices.

NC 55–65Very noisy. Shouting at 3 ft. Mechanical rooms, workshops.

NC 65+Extremely noisy. Communication difficult. Industrial spaces only.