Articulation Class (AC) is a single number rating system that places an objective number on the ability of acoustical materials to attenuate distracting noises that can occur in adjacent cubicles of an open office environment. It measures how effectively ceilings, walls, and office furniture provide sound attenuation in this environment.
This rating is especially important in areas like an open office layout where noise can distract workers and affect their productivity.
ASTM Test Procedures
The AC of a material is measured per ASTM E1110/E1111 test procedures. A random sound field is introduced into one of a pair of simulated adjacent work cubicles in a special large test chamber in the laboratory which includes the acoustical material being tested, typically a ceiling panel system.
These simulated cubicles are separated by a 5' high partial-height divider. A sound source is activated in one of the two cubicles. The attenuation between the source cubicle and the receiving cubicle is then measured at varying distances from the partial-height divider.
Since the higher frequencies, i.e. > 1000 Hz, are the most distracting, the sound attenuations are weighted more heavily at the high frequencies. From these weighted attenuations, the overall Articulation Class (AC) is calculated.
The better material is at absorbing sound, the higher its articulation class. An AC below 150 is not considered effective in achieving acceptable privacy in an open office environment. Acoustical ceilings having a noise reduction coefficient of 0.55 will have an AC of approximately 150. A ceiling AC above 180 is recommended for adequate privacy in an open office.
NGC Testing Services is unique in that we have the laboratory facilities to offer AC testing and CAC (Ceiling Attenuation Class) testing, along with several other hard-to-find tests for ceiling systems.