The subject of acoustics, often perceived as somewhat of a dark art, is something that needs to be considered on almost every project in the façade industry. Whilst this is an extensive and detailed topic we have set out below a few basic principles.
Sound is measured in decibels (dB) on a logarithmic scale, which means that a sound of 50 dB is 100 times louder than a sound of 40 dB. The Human ear has a large audible range and at the threshold of pain, the dB is roughly 1 million times greater than at the threshold of hearing.
The main consideration when reading specifications and test results is that a sound difference of 3 dB or less is barely audible to the human ear, whereas a sound difference of 5 dB is clearly audible. It is easy to look at minor differences between specification and test results and whilst numerically they may not be aligned, in practice the difference is so small that it will not materially affect the end installation. This is where a pragmatic interpretation of test results is required rather than a theoretical or literal comparison. Due to this, if you are doing acoustic testing, it is worth considering taking the average result over a range of tests if you get a minor failure as subsequent tests with all the same inputs and the same test rig, can give different results.