Home Engineering Building Acoustics
A puzzled engineer once called an acoustician friend of his to ask whether a door with a gap underneath could achieve a sound reduction index of 30 dB. On being answered negatively, he then announced that he had been given a test report by the contractor boasting of 35 dB. That “test report” happened to be a mere sound reduction index versus frequency curve without any description of the measurement conditions; the fact that there was no trace of leakage (which would have induced a flattening of the curve) was highly suspicious too. After much shouting on the phone, the full measurement report was eventually handed over. It turned out that the test had been performed on the door panel alone (without any frame or gap for that matter).
Lesson Learned: Do not trust an incomplete test report.
A manufacturer had in his catalog a roofing system that apparently featured better acoustic performances than the competition.
On looking earnestly at the test report, one sentence read: “The panel was laid on the structure.” This was the clincher: There was no fastener, which helped gain a few dB, and would of course never work in practice.
Lesson Learned: Always read carefully the test sample description as well!
A manufacturer’s representative would boast that his ceiling was simultaneously highly absorptive and featured high insulation performances. When requiring the relevant test reports, a technical file was sent back. The relevant test reports were printed out in small characters (usually a bad sign for sure!), the test laboratories were different for the absorption test and for the insulation test, and the name of the product appeared to have been tampered with. It eventually turned out that the representative had taken his best absorptive ceiling and his best insulating ceiling and attempted to pass them for a single material.
Lesson Learned: Reading a test report often is a case of finding where the clincher is!
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