The present technique for measuring the airborne sound insulation of wails and floors, involving measurements in 16 one-third octave bands, is tedious and expensive. The method provides more information than is needed for most purposes, and is more suited to research.
Several investigators have proposed the measurement of the overall A-weighted sound level difference using a sound level meter, with a broad band source of white or pink noise. Consistent results have been obtained but their relation to accepted rating methods such as STC is rather empirical.
The reference curves used for airborne sound insulation, i.e. STC and HPWG are very similar to the A weighting curve, and if the latter were adopted as the reference curve, there would be a firm theoretical basis for measurement with a sound level meter. Measurement of the difference between the linear sound level of a source of white noise, and the A weighted received level would in practice be a test of the conformity to the A weighting curve of the transmission loss curve of the partition. Adverse deviations would show as a higher received level. Favourable deviations would have little effect.
A study of practical walls andfloors, taken from National Building Studies Research Paper 33, showed that there was good correlation between the sound level difference calculated as i fit had been measured directly with a sound level meter, and a proposed rating method similar to 1S0 R717, but using the A weighting curve as the reference curve. Ninety-six per cent of results were within +_ 1 dB.
The practical diJ~culties of achieving a reasonably flat transmitted spectrum, and of correcting for room absorption will r.educe this precision, but bearing in mind the practical success of other short tests, the proposed test should provide a rapid test which is adequate for approval purposes.