The Importance of Articulation Class and Ceiling Attenuation Class Ratings for Offices

August 17, 2023   -  

What Is Articulation Class?

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.

AC ratings are represented by a numerical value, typically ranging from 100 to 250 or more. The higher the AC rating, the better the partition is at attenuating sound and preventing sound leakage between the spaces it divides.

When selecting partitions for a building or room, it's important to consider the desired level of acoustic privacy and noise control. A higher AC-rated partition is suitable for areas where confidential conversations or quiet environments are necessary, while a lower AC-rated partition might be adequate for less sensitive spaces.

What Is Ceiling Attenuation Class?

Ceiling attenuation class (CAC) is a rating system used to measure the sound-blocking or sound-reduction properties of suspended ceiling systems.

Ceiling tiles and panels are often the main components of the suspended ceiling system. They are installed in a grid formation, creating a barrier between the occupied space and the area between the suspended ceiling and the structural ceiling.

The CAC rating is represented as a numerical value, typically ranging from 0 to 40 or more, and it indicates the ceiling's ability to block sound transmission between adjacent spaces. The higher the rating, the better the ceiling system can reduce the amount of sound passing through it, providing better acoustic privacy and comfort.

Test Procedures for Articulation and Ceiling Attenuation Class

Articulation class and ceiling attenuation class are measured through specific acoustical testing procedures, which are outlined below.

Articulation Class Testing

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 AC is calculated.

The better the 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.

Ceiling Attenuation Class Testing

The ASTM E1414 standard is commonly used for conducting CAC tests.

CAC testing involves setting up a representative section of the suspended ceiling system in two adjacent rooms with a common ceiling plenum, with one side designated as the source room and the other as the receiving room.

A loudspeaker generates standardized sound signals in the source room across a range of frequencies from 125 Hz to 4,000 Hz, and microphones in the receiving room record the sound levels as the sound travels through the ceiling system. Data collected at various frequencies are used to calculate the CAC rating, representing the overall sound-blocking performance of the ceiling system.

Higher CAC ratings indicate better sound reduction properties, ensuring improved acoustic privacy and comfort in the spaces below the suspended ceiling.

Benefits of Acoustical Testing for Office Environments

AC and CAC ratings are essential considerations for office spaces due to their significant impact on acoustic privacy and overall comfort. Here's why these ratings are important:

  • Noise Control: Excessive noise levels can lead to distractions and reduced productivity among employees. A high CAC-rated suspended ceiling system can effectively block sound transmission between floors, limiting noise from above or below and creating a more peaceful and focused working environment.
  • Privacy: Offices often require confidential discussions and sensitive conversations. High AC-rated partitions help prevent sound leakage, ensuring that conversations in one office do not disturb neighboring spaces, enhancing acoustic privacy.
  • Collaboration: While privacy is crucial, collaboration is also essential in office settings. Properly rated partitions and suspended ceilings can create acoustically balanced spaces, allowing for effective communication and teamwork without excessive sound interference.
  • Compliance: Many building codes and standards require specific levels of acoustic performance for office spaces. Ensuring that partitions and suspended ceilings meet the necessary AC and CAC ratings helps comply with these regulations.

By carefully considering these ratings in office design and construction, businesses can create functional, efficient, and comfortable spaces that promote productivity, communication, and employee well-being.

Boost Office Productivity With AC and CAC Testing

Articulation class and ceiling attenuation class ratings play a key role in determining the acoustic performance of partitions and suspended ceilings, directly impacting acoustic privacy, noise control, productivity, and overall comfort.

By conducting proper acoustical testing, office spaces can achieve the right balance between privacy and collaboration, reduce distractions and stress, and ensure regulatory compliance.

NGC Testing Services is unique in that we have the laboratory facilities to offer AC testing and CAC testing, along with several other hard-to-find tests for ceiling systems.

Rely on NGC Testing Services for all your acoustical testing needs. Contact our team of experts today to get started.

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This post was originally published in September 2021 by Bob Menchetti and was updated and republished in August 2023.


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