'A' weighting (dB(A)) | A frequency dependent correction which weights sound to correlate with the sensitivity of the human ear to sounds of different frequencies. |
Ambient noise | A measure of the typical noise (excluding any unusual events)present at a site. This is usually described in terms of LAeq, T. |
Anonymous noise | Noise that cannot be attributed to a single (specific source). For example, noise from cars on a road would be considered anonymous whereas a noisy ventilation unit would not. |
Audible | Sound that can be heard or is perceptible by the human ear. |
Background noise | A measure of the underlying noise (excluding any unusual events) which is present at a site before a new noise source is introduced. This is usually described in terms of theLA90level: the sound pressure level exceeded for 90% of the time. |
Ctr Spectrum adaptation term | A correction added to a sound insulation quantity (such as Rw) to take account of a specific (traffic noise) spectrum. See BS EN ISO 717-1:1997. For example the difference between internal and external traffic noise levels in dB(A) is calculated using RW+Ctr (equivalent to Rtraffic) |
Clearly audible | There is no acoustic definition for clearly audible and as such a noise source may be deemed to be clearly audible if it is both easily identifiable and deemed likely to adversely affect the amenity of residents of any (proposed)development. |
CTRN | Calculation of Road Traffic Noise (ISBN 0 11 550847 3). A memorandum issued by the Department of Transport in 1988 which provides guidance for assessing the impact of non-complex traffic noise. |
CRN | Calculation of Railway Noise (ISBN 0 11 551754 5) A memorandum issued by the Department of Transport in 1994 which provides guidance for assessing the impact of non-complex railway noise. |
DMRB | The "Design Manual for Roads and Bridges" (DMRB) was introduced in 1992 in England and Wales. The DMRB sets a standard of good practice that has been developed principally for Trunk Roads. It may also be applicable in part to other roads with similar characteristics. (Volume 11, Section 3, Part 7 covers Noise and Vibration) |
Dne, W Weighted element normalized level difference | A single-number quantity which characterizes the airborne sound insulation of a small building element. See BS EN ISO 717-1: 1997. |
DnT, W standardised level difference | A single-number quantity which characterizes the airborne sound insulation between rooms. See BS EN ISO 717-1: 1997 |
Decibel (dB) | A unit used for many acoustic quantities to indicate the level of sound with respect to a reference level. |
ECP | Environmental Control and Protection Team, a service within the Public Protection department of Wiltshire Council. |
Façade measurement | Noise measurements made outside an external wall of a structure (usually 1 metre from the wall). |
Habitable room | A room used for sleeping or recreation / relaxation. |
Inaudible | Sound that cannot be heard or is imperceptible to the human ear. |
Industrial-type noise sources | Noise sources that are industrial in character. For example noise from plant and machinery, materials handling operations, or manoeuvring of heavy vehicles. |
Institute of acoustics | A professional body representing persons at all levels working in the field of acoustics. Institute of Acoustics (IOA) (opens new window). |
LA90, T: | Sound pressure level exceeded for 90% of the measurement period "T" or 'background level'. |
LAeq, T | Equivalent continuous sound pressure level measured over the time period "T". |
LAmax | The maximum RMS a weighted sound pressure level. |
Mixed use | Premises or development which will include both residential and non-residential uses. |
Noise | Unwanted sound. |
Noise with a specific character | Noise has a specific character if it contains features such as a distinguishable, discrete and continuous tone, is irregular enough to attract attention, or has strong low frequency content. |
Noise assessment | Evaluation of noise climate by a suitably qualified person to assist in the determination of a planning application. |
Noise-sensitive premises / developments | Principally comprising residential premises, hospitals, schools and hotels. Other premises types may be deemed such depending upon circumstances. |
Noise nuisance | A legal term used to describe noise at a level that is disturbing as perceived by a reasonable person. The meaning of nuisance is defined by precedent in common law. |
Outdoor amenity area | An outdoor area adjacent to a residential building which is designed and intended primarily for the leisure and recreation of the occupants of the dwelling. This will include gardens, landscaped areas, and balconies. |
R, Sound reduction index | A quantity which characterizes the airborne sound insulation of a material or building element in a stated frequency band. See BS EN ISO 140-3:1995. |
Rw, Weighted sound reduction index | A single-number quantity which characterizes the airborne sound insulation of a material or building element measured in the laboratory. See BS EN ISO 717-1: 1997. |
Rating level | The noise level of an industrial noise source which includes an adjustment for the character of the noise. Used in BS4142. |
Sound insulation | A quantity which is used to characterize the reduction in sound pressure level across an element or partition. (See R, RW, DnT, W, Dne, W, Ctr). |
Structure borne noise | Noise that propagates through a structure, for example through a building. |
Suitably qualified person | A person having a suitable combination of formal training and experience in the assessment of noise. Advice in the identification of suitably qualified persons can be obtained from The Association of Noise Consultants (opens new window). |