The BS EN ISO 10140-2: 2010 test involves placing the door construction within a dividing wall between a sound source room and a receiving room. Sound waves are produced in the source room and measurements of the sound pressure levels are made in both rooms at one-third octave intervals in the frequency range 100 to 3150 Hertz (Hz).
Several microphones are used to obtain a good average of the sound pressure level in each room. From these measurements, the Sound Reduction Index (R) is derived.
These values are then calculated in accordance with BS EN ISO 717-1: 1997 to obtain as single figure weighted sound reduction index (Rw). The ASTM method follows the same principle but performance is measured over a slightly different frequency range, 125 to 4000 Hz and the results are expressed as a sound transmission class (STC).
dB Decibel. A comparative figure generally indicating a decrease in sound level between two points (source and receiver). The dB scale is logarithmic so 10dB is 10 times the power ratio, 50dB is 100,000 times the power ratio and 100dB is 10,000 000 000 times the power ratio of 1dB respectively.
R Sound Reduction Index. Expressed in dB and defined as the number of decibels by which sound energy, randomly incident on the test sample, is reduced in passing through it.
STC Sound Transmission Class. A single figure performance indicator very similar to Rw but derived from ASTM-E413-10. Classification for rating sound insulation. The Rw or STC rating indicates acoustic performance of a door/seal assembly over a wide spectrum of sound frequencies.