EWPAA Structural Plywood and LVL Design Manual - Engineered ...

When it is required to add more than two sound sources they must be arranged in numerically increasingorder.For example, to add: 88dB, 89dB, 84dB and 86dB.Arranging in numerically increasing order: 84, 86, 88, 89For: 84 + 86= difference of 2dB.From TABLE 14.1, 2.1 dB is to be added to 86 to give 88.1dB.i.e.88.1 rounded to 88dB.Add 88 to 88dB giving a difference of 0.From TABLE 14.1, 3 dB is to be added to 88 to give 91dB.Add 89 to 91dB giving a difference of 2From TABLE 14.1, 2.1 dB is to be added to 91 to give 93.1dB.i.e.93.1 rounded to 93dB14.8 Sound Barriers (from Ref. 1) - Design ExampleThere are two designs to reduce traffic noise into a home. FIGURE 14.4 shows the sound paths fordiffraction and transmission.One consists of a solid filled concrete block wall giving a sound reduction of 35dBA.The other is 25mm thick timber giving a TL of 21dBA. Intuitively this may suggest the block structurewould give the best result.Sound Barriers – Worked ExampleNoise is received at the house, mainly by two paths.• diffracted rays over the walls;• transmitted through the wall.FIGURE 14.4: Sound pathsDiffraction can be attributed to a reduction of 10-12dBA, maximum. In this case take 12dBA.227