Accredited ASTM E90 Sound Transmission Loss



North Orbit Acoustic Laboratories provides independent, accredited ASTM E90 Sound Transmission Loss (STC) Testing Services.

Accredited ASTM E90 - Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements. ISO/IEC 17025:2017 accredited through A2LA Certificate 4240.01

Accredited Sound Transmission Loss - Measures sound transmitted through walls, floors, windows, doors and other building elements. Results provide ⅓ octave band Transmission Loss (TL) and Sound Transmission Class (STC) numbers. Data is used by acousticians, architects, and engineers to design and specify appropriate noise isolation between architectural spaces. NOAL is ISO/IEC 17025 accredited through A2LA Certificate 4240.01


Sound transmission loss tests are performed per a stringent protocol established by The American Society for Testing and Materials (ASTM). North Orbit performs these tests in accordance with ASTM and is fully accredited by A2LA. The result of the ASTM E90 test is a reportable STC number or STC rating.

ASTM E90 is conducted on a test specimen that is installed between two reverberation rooms in a test suite comprised of a source chamber and a receiver chamber. The two chambers and the E90 test are designed so that sound transmission between the rooms is only through the test specimen. Loud noise is created by a reference sound source which produces a continuous sound stream in the source chamber. In the receiving chamber, sound levels are measured and essentially subtracted from the sound levels in the source chamber. The difference represents the transmission loss value or STC value. The process for obtaining these numbers in the field, rather than the laboratory, is described by ASTM E336.


ASTM E90 is used in product development when acoustic issues such as sound isolation or sound reduction are a concern and/or selling point. An STC rating can be used to ensure compliance with a building code or other third-party requirements, and as a marketing tool to establish a competitive edge.


Sound transmission loss test results are used in architecture to select partitions and building elements such as windows and doors with appropriate acoustic ratings for their intended use. Architects typically look at single-number ratings, most frequently STC, while acoustic consultants will use the full set of ⅓ octave transmission loss (TL) values to more precisely calculate sound-isolating performance of assemblies in structures. Laboratory-derived STC ratings are used to demonstrate compliance with a building code or other client or third-party requirements. The ratings are also used as a marketing tool by developers to establish a marketing advantage by demonstrating their concern and attention to enhanced sound isolation in multi-housing projects. 

Building Materials / Research and Development

Sound transmission loss test results are used in product development when acoustic properties relating to sound transmission are of concern. This is true for building materials and systems used in demising partitions including gypsum drywall and other sheet goods, as well as insulation and framing materials such as steel studs. All of these have a profound impact on the sound transmission performance of a given assembly. 

Windows and Doors (and other elements inserted in openings in partitions)

Sound transmission data on doors, windows, and other elements, such as PTAC units (hotel style air conditioners), are required by acousticians to determine a composite performance for the entire partition by combining the data and areas of each element into a composite calculation.


Sound transmission loss testing can be used by any company needing to quantify the amount of sound their assembly or product is stopping. Sound transmission loss testing results can be used by architects and engineers to specify interior and exterior wall assemblies, windows and doors. Building material manufacturers need the data to provide their customers with accurate information regarding their materials and assemblies. Acoustical consultants need the data to make accurate predictions of sound levels the occupants or active or passive listeners will hear on opposite sides of partitions under specific noise conditions. 

ASTM E90 sound transmission loss tests and STC results are used in the architectural, engineering, building code/inspection, gypsum wallboard, masonry, window, door, PTAC, HVAC, insulation, glass, and other panel industries to name a few.


With 30 years of experience in acoustical testing and consulting, NOAL provides “above and beyond” service by interpreting, diagnosing, and problem solving your specific sound issues. NOAL's hard-working team is easy to work with and takes pride in making your job go smoothly.