Frequently Asked Questions

A residential noise survey quantifies the noise levels incident upon the various facades of a building or buildings, for the purpose of attenuating the noise to acceptable levels to protect the amenity of future inhabitants. Through long term noise monitoring, day and night time noise levels can be determined and referenced against a number of noise criteria from guidance documents such as BS8233 and ProPG. Acoustic glazing and acoustic ventilation can then be specified to ensure internal noise criteria is met.

Mitigation measures may also be required to ensure that maximum noise levels for external amenity (garden) areas are not exceeded. This is most often achieved through the design of acoustic barriers, or building orientation and positioning.

The survey may need to address a variety of noise sources from roads, railways, commerce & industry, animal or wildlife noise. As such, the survey may include additional components such as a railway noise assessment, a BS4142 assessment for commercial noise, or a sound insulation assessment if adjoined to a significant noise source.

An industrial noise survey determines the impact of factory noise at the nearest facade of any nearby dwellings. This typically involves a BS4142 assessment which references the rating noise level incident upon the residence against the background noise level, to give an assessment level. The rating noise level is the combined noise level from all the noise producing elements of the factory (including traffic noise) with a (dB) rating penalty added, to take into account the potential that the noise has to cause annoyance.

If the rating level exceeds the background noise level then a positive assessment level is generated which indicates an adverse noise impact.

If the rating level is less than the background noise level then a negative assessment level is generated which indicates a low noise impact.

A commercial noise survey is much the same as an industrial noise survey in that it typically takes the form of a BS4142 survey. The only real difference is that it generally applies to smaller businesses such as restaurants, take aways, shops and offices.

Because buildings are often built adjoining each other, a sound transmission test may also be required to determine the sound attenuation properties of a partition. This data can then be used to determine the potential for a noise impact through the wall or floor system.

An entertainment noise survey is used to typically determine the noise impact of music and / or patron noise from a pub or club on nearby residences. It is important for the music noise to be measured across the frequency spectrum as it is typically the lower octave bands (63Hz & 125Hz) that are most audible at distance. Assessment methods can vary between councils but it is generally desired that the noise is inaudible within the residence, or that external levels do not exceed background noise levels in octave bands.

Workplace noise assessments are required where there is the potential of a noise risk to any employee(s), to comply with NAW2005 and the HSE L108 ‘Controlling Noise at Work’ guidelines. Spot measurements taken around a site can provide a view of the average noise levels that employees are exposed to in a certain area. For employees that are exposed to more varied noise levels, dose badges are fitted to the shoulder to measure the noise level ‘at ear’ for long durations. This time data is averaged to provide a LEP,d level which is the noise exposure level over an 8 hour period.

The LEP’d is then referenced against action threshold levels which, if exceeded, trigger certain responsibilities that the employer is obliged to take on to reduce the noise risk. These include reducing noise levels at source, designating certain areas ‘hearing protection zones, the provision of hearing protection and employee health surveillance in the form of annual audiometry testing.

Railway noise can have a negative impact on residential amenity, both indoors and outdoors. WHO Environmental Noise Guidelines (2018) provides recommendations for a maximum Lden (day, evening & night) of 54dB, stating that railway noise above this level is associated with adverse health effects. It also recommends a maximum Lnight of 46dB, stating that railway noise above this level is associated with adverse effects on sleep.

A railway noise assessment uses measured noise levels from individual train passes to calculate the Lden and Lnight. Should either of these levels be exceeded, mitigation would be advised, usually taking the form of an acoustic barrier or building layout / orientation adjustment.

Room acoustics is the science of how sound behaves in an enclosed environment. A sound source within a room will radiate sound waves in all directions. The waves bounce off surfaces and scatter around the room in an extremely complex pattern. The waves decrease in energy over time as they are attenuated through contact with surface materials, particularly softer furnishings. It is therefor possible to control the sound to some extent, by room design, layout and by the application of sound absorbers and diffusors.

BB93 is a document that sets out minimum performance standards for the acoustics of school buildings, and describes the normal means of demonstrating compliance with the Building Regulations.

It is important to control acoustic characteristics such as Indoor Ambient Noise Levels, the sound insulation of partition walls and floors and reverberation times. This ensures an acoustically comfortable environment which promotes learning by enhancing communication and speech intelligibility. An acoustically comfortable environment has also been proved to reduce anxiety and promote well-being and good health.

Acoustic design plays an important roll in the creation of modern healthcare facilities. Patients have a right to be consulted privately, and to be treated and recover in a peaceful environment.

Health Technical Memorandum 08-01 provides advice and guidance on the acoustic design and construction of healthcare facilities. The document provides target criteria for the following main areas:

Ambient Indoor Noise Level (AINL): Maximum indoor noise levels for various spaces, and is a combination of noise ingress from both external noise sources, and building services such as air conditioning noise.

Partition Sound Insulation: Minimum sound insulation criteria for wall and floor partitions to ensure privacy and reduce noise ingress.

Reverberation: Whilst no specific reverberation times are specified, HTM08-01 recommends the installation of acoustic ceiling tiles of Class C or better, to cover a minimum of 80% of any given area floor space.

The purpose of Pro-PG is to standardise new build residential noise assessments which are (mostly) exposed to traffic noise. A ProPG assessment promotes good acoustic design through the consideration of features such as building layout and orientation, to provide a good level of protection for all habitants against excessive noise levels. The document proposes a two stage risk assessment.

Stage 1 quantifies the risk of adverse health effects from day and night time noise levels.

Stage 2 is a noise assessment and explores the possibility of noise control to reduce the noise impact on future habitants.

BS8233:2014 provides guidance for controlling noise in and around buildings. Crucially, it provides criteria for maximum internal residential noise levels, and provides extensive information about sound insulation and to achieve these criteria. The standard also covers different noise sources, building types and building services noise.

BS4142:2014+A1:2019 provides the methodology for executing a noise impact assessment to quantify the impact of commercial and industrial noise at a noise sensitive receptor (NSR), typically a dwelling or dwellings.

The offending noise sources are determined at the receptor and a penalty is applied to reflect the ‘annoying’ characteristics of the sound. This ‘rating level’ is then referenced against the background noise level to provide an assessment level. If this level is too high, mitigation may be required so that the noise source and the receptor can co-habit without complaint.

Sound insulation testing determines the sound attenuation of a partition or structure. Typically, pink or white noise is blasted on one side and measured both in the source room and the receiving room. The difference between the two is the sound transmission loss and this can be presented in individual frequency bands or as a discrete number, usually weighted to reflect certain frequency content.

Pre-completion sound testing is often required for new and converted dwellings to satisfy building regs Part E. Testing provides a single number quantity which is referenced against the following criteria to determine if the partition provides adequate sound insulation for habitation.

Sound insulation is the ability of a partition or structural element to attenuate sound.

Transmission loss is the decrease in sound energy when passing through a material or structural element.

A sound absorber is a material that turns sound energy into heat. Every material will absorb a certain amount of sound energy and reflect the rest. The level of absorption varies throughout the frequency range, and from material to material.

A good absorber will allow sound to easily penetrate the material, where the sound energy is turned into heat, through frictional losses within the material.

As sound diffuser scatters sound waves in many directions by reflection off an uneven surface. In a perfectly diffuse space, the reverberation time will be the same at any point in the room.

NANR45 is a methodology for low frequency noise assessment, with emphasis on disturbance and the generation of complaint.

Rw is the weighted sound reduction index. It is a single number which reflects the sound insulation of a material over a large frequency range. It is determined by laboratory measurement and used to characterise the sound insulation properties of building materials and building elements.

DnT,w is the Weighted Standardized Level Difference, the in-situ airborne sound insulation properties of a partition or structural element, and is determined through sound insulation testing.

LnT,w is the weighted standardized impact sound pressure level. Where DnT,w refers to airborne sound insulation, LnT,w refers to impact sound insulation and characterises the ability of a material or structural component to resist the transmission of structural vibration.

Acoustic glazing is glazing that has been specially design to attenuate sound. A good example is double glazing where the glass panes are often laminated with a PVC layer which provides resilience and reduces sound transmission. Glass panes are also made with differing thicknesses which provides further sound reductions.

Reverberation is time taken for a sound to decay within a space and is determined by the surface materials within the space.

A Dose badge is effectively small noise meters, typically attached to the shoulder of a work employee to measure the noise level ‘at ear’ over prolonged time period, usually 8 hours.

LAeq,16hr is the equivalent continuous sound level in dB(A) over the period 07:00 to 23:00. In layman’s terms, the average daytime noise level.

LAeq,8hr is the equivalent continuous sound level in dB(A) over the period 23:00 to 07:00. In layman’s terms, the average night time noise level.

LAFMax refers to the greatest A-weighted noise level event measured over a certain time period, with a ‘Fast’ measurement setting.

A-Weighting is a weighting curve that is applied over the frequency spectrum of a sound, to reflect the way the sound is interpreted by the human ear.

LEP,d is the average noise level that an employee is exposed to over an 8hr period.

A common mis-conception is that background noise is all you can hear without the offending noise present. In fact, background noise, or LA90 is the lowest 10% of everything you can hear.

White noise is a ‘man made’ random noise generated from all audible frequencies combined. Sound energy has equal power per unit bandwidth.

Pink noise is similar to white noise except that it has equal power per percentage band width. Pink noise is also much closer to noises that occur naturally in nature such as waterfalls and rain.

Brown noise is noise created from Brownian motion.

Ambient noise is everything audible at a period in time.

The specific noise level is a BS4142 term that refers to the offending noise measured or calculated in the absence of any residual noise.

The rating level is a BS4142 term that refers to the specific noise level, adjusted by the addition of a rating penalty which characterises the nature of the noise and is designed to reflect the subjective ‘annoyance’ that the noise may generate.

The rating penalty is a BS4142 term that refers to the penalty in dB that is applied to the specific noise level to reflect the subjective ‘annoyance’ that the noise may generate.

Octave bands are frequency bands, the bandwidth of which equals one octave. Typical octave bands used in acoustics are 31.5Hz, 63Hz, 125Hz, 250Hz, 500Hz, 1kHz, 2kHz, 4kHz and 8kHz.

Breakout noise is the noise that leaks from within a building, to the outside world.

Noise ingress is noise that originates from outside or another space, and is transmitted into the receiving space.

A NSR is a Noise Sensitive Receptor. Typically a residential building, it refers to a location where annoyance and complaint may be generated by excessive noise of some nature.

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