Excessive and intrusive noise levels are a major bugbear of modern living. As we come under increasing pressure for living space, dwellings are becoming more tightly packed and residential developments are being built in spaces that might previously have been considered unsuitable – next to major roads or railway lines for instance.
However, noise need not be a ‘showstopper’ for the development of such sites – an effective array of noise control strategies can be implemented to ensure the sustainable development of even the noisiest of sites. Before we examine these, let’s take a look at how noise is measured – and just how loud is ‘loud’.
Most of us will have heard of the sound being measured in decibels (dB). However, a simple decibel measure does not give a true representation of how loud a noise is. This is because the human ear hears different frequencies (pitch) in the sound differently.
For example, to the human ear, an 80dB sound at the frequency of 100 Hz (a low frequency) will sound around four times quieter than an 80dB level at a frequency at 1000 Hz.
So, to make dB levels more meaningful we apply something called “A-weighting” to the noise we measure. This reflects the way that the human ear hears noise across all frequencies – and gives us a measurement in dB(A) which give a better overall indication of how noisy something is.
So how loud is ‘loud’?
We can think of the dB(A) scale beginning at zero - which is the threshold of human hearing. In broad terms, each 10dB(A) increment can be considered as a doubling in noise level. So, a level of 20dB(A) would be typical of a remote country location without any identifiable sound, and a level of 30dB(A) the sound level in a quiet bedroom (with windows shut).
Moving up the scale, the level of conversational speech is around 60dB(A) and a vacuum cleaner around 70dB(A). The sound level kerbside of a busy road is around 80dB(A). Prolonged exposure to noise at this level is likely to cause permanent hearing damage.
In a night club you will experience sound levels of 100-110 dB(A), and you will not want to be anywhere near 130dB because you will experience physical pain!
How to develop noisy sites
Having established how noisy a development site is, we can develop strategies for reducing noise. For residential developments, this not only requires consideration of the noise experienced by occupants within the building, but how noise levels will affect private or communal amenity spaces. So what strategies can be considered?
Quietening the source – reducing road or rail traffic noise at source is possible (for example, in the case of road traffic, through the use of low noise road surfaces). Since the surfacing of roads is a matter under the jurisdiction of Highways England or relevant local authority, quietening source noise is not a strategy routinely available to developers.
Attenuating the noise – noise reduces with distance. So moving proposed development as far as possible from noise sources may be useful and help limit the extent of overall mitigation required.
Obstructing the sound – solid fences, earth bunds and buildings can all be used to provide useful acoustic screening. Early input into the master-planning of developments should be provided to integrate effective acoustic screening.
Sound insulation of the building envelope – even if a site is subject to high noise levels, modern building techniques can provide facades with high levels of sound insulation. For example, whilst standard thermal double glazing will typically offer a sound reduction of around 30dB, modern acoustic glazing systems, incorporating special laminated glass, can increase the performance to over 50dB. So, solutions for providing noise control at even the noisiest of sites are available.
It is, however, important to note that sound insulation will only be effective when windows are closed. This means that in addition to suitable glazing, an effective sound insulation scheme will also need to make appropriate allowances for alternative means of ventilation – so that residents are not reliant on opening their windows for fresh air. Again, recent advances in ventilation technologies now give the developer a choice of possible ventilation solutions including acoustically rated passive (natural) ventilation and proprietary, energy efficient mechanical ventilation options.
As there is increasing pressure on sites available for residential development, so we have to look more closely at how to create tranquil living spaces in potentially noisy locations. With continued technical development and accurate sound analysis, more urban spaces are becoming viable, offering opportunity for much needed housing development.