Approved Document E sound testing is carried out when the property is fully finished. The aim of on site sound tests is to determine if a ‘reasonable’ resistance to the passage of sound has been achieved by the construction method and whether the installation has met the minimum requirements of the standard (or not).
In the ideal world, all of the installed materials will perform at their best, however, this does not typically occur on site, the structure can make a significant difference to the test results by enabling sound to travel through the building by indirect means, this is referred to as flanking.
Flanking creates a reduction in performance over lab tested conditions, typically flanking will be related to the construction junctions between the floor, the ceiling and other walls, the acoustic interactions of materials, the presence of supporting joists, close set windows, poor performing door seals, ducts, grills and a number of other problems including room sizes and finishes. These are all typical factors associated with installation and are often a consideration due to the restrictions of some buildings, particularly conversions.
Onsite, the achieved performance is a combination of the separating party wall (or floor) element plus any other sound transmission that travels via other pathways through the structure (flanking). As these flanking elements will not be present within a laboratory setting then the results are generally better within a laboratory set of sound testing results. This is where the developer must exercise caution in relating the manufacturers lab tested results to a real-world prediction.
The drop in performance (for real world) has long been considered as 5dB with a drop in performance of 3dB to 8dB being typical for lightweight partitions. However, these are simple ‘finger in the air’ values and must not be relied upon. It may be tempting for developers to design to meet the minimum standard, why? to save material costs, but it is not unusual for an acoustician to test a structure and determine that a 15dB reduction has occurred when compared with the laboratory data.
Achieving good sound insulation standards, particularly where the building may be restrictive can be a challenge and onsite testing can throw up unexpected sound testing performances (good and bad). Employing and acoustic consultant at an early stage for site visits, plan review and even construction design to meet the Approved Doc E standard will help to ensure that your project achieves the ADE standard and that the sound testing requirements are achieved. Contact us today for more information