We have had a busy year preparing Noise Impact Assessment Reports for aviation noise. These reports are prepared almost exclusively in response to requests for further information (RFI’s) by the relevant local authorities. We though we’d share some insights into how buildings can be designed to keep out aircraft noise.
We first need to fully understand what it is we are trying to keep out. Aviation noise pollution is the unwanted by-product of an aircraft in flight. The individual components that make up the noise of an aircraft in-flight are:
For an aircraft designer, this information is vitally important. For us acousticians, it is useful information, but we are more interested in the sum-total of these individual noise components. In other words, acousticians are more interested in what our sound level meters are reading on the ground, as this is more relevant to what will be experienced by the occupants of a home.
Specifically, acousticians and architects want to know (inter alia):
The peak noise level during an aircraft flyby.
The average noise level during a day and/or night period during which aircraft flew by.
The overall frequency spectrum of the noise.
The World Health Organisation (WHO) recommends that for a good night’s sleep, the equivalent sound level should not exceed 30dB(A) if negative effects on sleep are to be avoided, and individual noise events exceeding 45dB(A) should be avoided.
Let’s take an example: A noise survey taken at the location of a proposed dwelling in a rural area shows the equivalent sound pressure level to be 45 dB(A), but an individual noise event clocked 65 dB(A) during once particular flyover.
The dominant noise source was aircraft noise.
As a rough guide, the envelope of the dwelling should therefore be designed to reduce external noise by at least 20dB’s.
This is of course an over-simplification but the principle is the same: (a) set a design target for internal noise levels; (b) take a representative sample of the outside noise & (c) design the building envelope to the appropriate levels of sound insulation.