Noise Expert (acoustical engineers) measured the Field Sound Transmission Class (FSTC) for seven different walls in a Lockheed Martin office building.  The building was going to be remodeled and some of the rooms were going to have sensitive activity that required an FSTC 50.

Airborne noise isolation addresses noise sources such as televisions, stereos, human speech, etc.  The Sound Transmission Class (STC) is a single-number rating of the sound transmission performance for a partition tested over a standard frequency range. The higher the STC, the more efficient the partition is for reducing sound transmission between spaces.   The following is a list of STC descriptions which corresponds the single-number STC rating to a subjective evaluation of a typical listener. The STC descriptions are based on the audibility and intelligibility of speech between two spaces, and assume relatively low background noise. Keep in mind that the subjective descriptions below are based on typical human speech. Low frequency noise, such as from music, will be more easily audible than speech.

STC 30         Normal speech can be heard and easily understood
STC 35         Loud speech can be heard and easily understood
STC 40         Loud speech can be heard and moderately understood
STC 45         Loud speech is audible, but will sound “muffled.”
STC 50         Loud speech is difficult to detect. An occasional word may be understood.
STC 55         Loud speech is not audible.

Noise Expert conducted FSTC test in accordance with ASTM E336, Standard Test Method for Measurement of Airborne Sound Insulation in Buildings and ASTM E966, Field Measurements of Airborne Sound Insulation of Building Facades and Facade Elements. The FSTC will be calculated using ASTM E413, Classification for Rating Sound Insulation.

Please let us know if you have any questions or if you would like our assistance with acoustical evaluations. 480-332-9325,, Noise Expert (acoustical consultants) –

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