Sound Transmission Class (STC) |
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The
Sound Transmission Class is a single number rating of the effectiveness
of a material or construction assembly to retard the transmission of airborne
sound. The sound transmission loss between the source and receiving rooms
are plotted on a graph by frequency and sound level in decibels. The STC
curve is a sliding contour that is fitted to the performance data plotted
in a manner that will allow no more than 32 deficiencies below the appropriate
contour. The maximum deficiency at any given frequency shall not exceed
8 decibels Once the appropriate contour has been selected the STC is determined by the decibel value of the vertical scale at 500 Hz. The STC is expressed as a single STC number (Example STC 32) Note that the STC contour is similar to the inverse of the equal loudness contour, insofar as it discounts the lower frequency sounds to reflect how our ears perceive the lower frequency sounds.
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