Despite the old adage whatever the construction undertaken in the test lab should be replicated as close as possible on the construction site; unfortunately, it is very difficult to build to the stringent standards of the laboratory.
When the construction assembly is tested in the lab, it is also certified and an exact description of the materials and the installation techniques are described in detail. These too should be replicated on the job site as close as possible. However, it is not always possible to replicate the exact conditions on the job-site compared to the ideal conditions normally present in a lab setting, which is the reason why a 5dB point difference is allowed between the construction design on paper and the actual on site sound test performance.
The method by which the STC is arrived at also takes into consideration as to how we actually perceive sounds. Our sense of hearing is sensitive to low frequency sounds and thus the STC curve takes that into consideration at the various frequencies.
Another little known fact about sound does not pass through a wall – unless there is a crack or gap. The sound energy sets the wall in motion and the wall itself becomes the transmitter much like a radio wave that energizes a radio speaker, which transmits the broadcast signal. The materials that comprise the wall and the manner in which they are installed can have a great bearing on the performance of the wall and could greatly effect the result or your Part E sound test.
In a nutshell it is ultra important that installation details are closely followed to ensure that the ‘onsite’ sound testing results are as close as possible to the laboratory.
If you would like more information in regards to sound testing please contact us at info@aptsoundtesting.co.uk or call us on 01525 303905.