A number of factors affect the transfer of noise into and within a strata building. These include:
- The external and internal walls materials. Heavy, dense materials such as masonry or brick walls are better for sound reduction, but there are also lightweight solutions. For example, interior walls that have layers of plasterboard with sound-control material in the cavity can be very effective in reducing noise.
- Windows and doorsare often the weakest link in sound insulation. Double glazing is particularly effective for windows, especially if the airspace between the two panes is as wide as possible. Solid-core doors are best, particularly for those that open on to external areas. All gaps and openings around both doors and windows should be well sealed – even the smallest openings can leak significant amounts of noise. Thick curtains are more sound absorbing than blinds.
- Construction of the floor.Concrete slab and its thickness or lightweight timber frame (this may be an issue for older buildings). The thickness of the drop ceiling in the apartment below (if installed).
- Type of flooring cover. Basically tiles, floor boards carpet with a range of other finishes that perform in a similar way to one or the other of these.
- Type of flooring underlay.Generally the softer the underlay the better the performance but this is limited by effect of entrained air and the need to maintain a solid substrate for tiles. Carpet ages, and so does underlay. While there may be a strict compliance, for example, with a by-law that stipulates in a proscriptive sense that a floor (apart from a wet area) is to be covered by carpet and underlay, there may be technical compliance with the strict letter of the by-law at the time of installation, but there may still be noise disturbance directly related to the type of flooring installed, despite it being carpeted with appropriate underlay. There is a huge difference in the acoustic properties of underlays and similarly there is a wide variety in the range of types of carpet and their weight.
- Hard surface flooringwhich abuts skirting boards with no separation between the two elements aids in the transmission of noise laterally as well as vertically.
- Flooring installation errorssuch as nails through underlay, bridging of the perimeter gap, incorrect underlay etc.
- Internal furnishingssuch as curtains, lounges and chairs with cushions all assist to absorb sound in a lot. Remember the noisy restaurant with polished concrete floors, no soft furnishing, but hard chairs and no curtains.