Airborne Sound Transmission Loss

Increase your building product’s noise insulation by understanding its sound transmission loss

Differentiate your product and ensure you meet the necessary requirements of noise insulation through sound transmission loss testing. Gauge how your building product or system will isolate noise from one area to an adjacent area. This includes the sound transmission loss from two rooms inside a building or from the outside of a building to the inside of the building.

By partnering with Intertek to help you understand your building product’s noise insulation, you gain access to accurate acoustical performance measurements and reduced turnaround times. With our experience testing to AAMA, ANSI, ASTM, ISO, and SAE standards, we can help evaluate the sound transmission loss of your products.

What is sound transmission loss?

Sound transmission loss (TL) is a measurement of how much airborne sound is blocked by a building partition. The TL of a partition is measured by generating broad band noise in one room, and measuring the sound pressure levels (SPLs) in both that room and the adjacent room (an example of this test setup is shown above).

Sound Transmission Loss Ratings:

Sound Transmission Class (STC): A single number rating used to evaluate the performance of a wide variety of building elements in a laboratory. These building elements could include floor/ceiling assemblies, doors, walls, windows, curtain walls, skylights, louvers, roof systems, etc. This rating is also used for exterior facades and façade elements in some cases.

Outdoor-Indoor Transmission Class (OITC): A single number rating used to evaluate the noise isolation of exterior walls and façade elements that are exposed to transportation and other low frequency noise sources in a laboratory.

The STC and OITC ratings are calculated from 1/3 octave sound transmission loss test data obtained in a controlled laboratory environment.

For Information on field testing for Apparent Sound Transmission Class (ASTC) and Apparent Outdoor-Indoor Transmission Class (AOITC) ratings, click here.

Which types of products benefit from sound transmission loss testing?


Laboratory Test Equipment

  • Reverberation Chambers for specimens up to 14’ x 10’ x 12”
  • National Instruments/ ViAcoustics Trident Analyzer
  • 29mm, 57mm, and 100mm Impedance Tubes

Field Test Equipment

  • National Instruments/ ViAcoustics Trident Analyzer
  • Microphones & Preamplifiers
  • Loudspeakers
  • Tapping Machine
  • Reference Sound Source
Need more information? Click here

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