Brüel & Kjær Sound & Vibration Measurement A/S
based in Nærum, DENMARK
Sound energy does not remain in the room where it is produced, but propagates throughout the building by any available path, intruding into other rooms as noise. Each country has its own standards of sound insulation in buildings, but it is measured in the same way all over the world. The noise levels in the two rooms under investigation are measured and subtracted, and the level difference is corrected for the influence of the reverberation time and background noise level in the receiving room. The measurements and calculations are made in 1/1- or 1/3-octave bands and averaged over a number of positions in the rooms. Finally a single-number index is calculated by averaging over all the frequency bands.