Laboratory & Onsite Sound Testing

The Difference Between Laboratory & Onsite Sound Testing
Despite contractors best endeavours to install the acoustic materials exactly as per the installation instructions; 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 and followed to the letter, obviously this should be replicated on the your site as closely as possible. However due to time constraints etc, 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 construction performance and subsequent sound testing.

The method by which the STC is arrived at also takes into consideration as to how we perceive sound. Our sense of hearing is sensitive to low frequency sounds and thus the STC curve takes that into consideration at the various lower frequencies.

Another little known fact about sound is it doesn’t 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 make up the wall and the manner in which they are installed can have a great bearing on the performance of the wall and can greatly affect the sound test, i.e. if the wrong fixings are used which prevents adequate insulation between materials this can a=easily lead to a sound test failure.

It is very important that installation details are closely followed to ensure that the onsite results are as close as possible to the laboratory.

We have produced a list (shown below) of the major problem causes that can arise during our experience during on site sound testing and sound test design and construction. (It’s worth noting that some items may not apply to your type of construction).

1. Ensure that the sub-floor is watertight and sealed with mastic or silicon.
2. If installing floating screed ensure all isolation layer joints are overlapped and taped.
3. Ensure that the Acoustic floor is fitted with staggered joints.
4. Ensure all the Acoustic floor is sealed watertight even around heating pipes.
5. Do not nail or screw through an Acoustic Floor.
6. Do not screw plaster board into joists, when using Resilient Bars.
7. Ensure the insulation fills the whole width of void, also pack around pipe work.
8. Ensure that the plasterboard on any walls is complete right down to sub-floor, seal all gaps.
9. Ensure you use the isolation tape around the wall of each room.
10. Ensure plasterboard is fitted with staggered layers and all joints sealed.
11. If using Resilient Bars ensure that they are fitted as per manufacturer’s recommendations.
12. Ensure all Fireplaces are blocked up with brick or plasterboard.
13. Ensure that any RSJ’s or supporting steel work is insulated and isolated from plasterboard.
14. Ensure all waste pipe service runs are boxed in with insulation and plasterboard.
15. You must fit doors and windows before the test is carried out, to stop noise transference.

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Business:             APT Sound Testing