A noise impact assessment or noise assessment is something which generally follows a noise survey. The purpose is to determine how a generated noise affects a receiving point or multiple receiving points, be it existing or future proposed. In order to carry out a noise impact assessment it is necessary to know two parameters, the noise which needs to be assessed and the existing noise in which to assess it against.

It is usual for noise impact assessments to assess the resultant or generated noise expressed as the LAeq,T against the existing background noise level represented as the LA90.

For reference, the LAeq,T is the A-weighted 'equivalent continuous noise level' which is an average of the total sound energy measured over a specified time period, and the LA90 is the A-weighted noise level exceeded for 90% of the measurement duration (T).

An example of a typical noise impact assessment methodology is that of former British Standard 4142: 1997, ‘Method for Rating industrial noise affecting mixed residential and industrial areas’. BS 4142 compares a rating level against the existing background LA90 level in order to determine an excess of rating level above the existing background level. In other words, how many decibels the contribution of generated noise either is, or will be against the existing background. The difference between the two parameters above e.g. -10 or +5 dB etc, can then be used to assess the actual or predicted noise impact.

In addition to the example above, Local Authority’s can request a number of other types of noise impact assessments to be carried out on a site depending on the existing or proposed usage be it industrial, residential, occupational, planning, transportation or otherwise. We aim to give guidance, undertake any noise survey or noise assessment / noise impact assessment and provide noise mitigation advice in connection with any client’s requirements.

For more information regarding noise impact assessments or to discuss any requirements that you may have, please visit the subsequent website pages attached to the ‘Services Tab’ above, or contact us using the details provided below.