Sound level meters are used in noise nuisance and domestic environments to assist with resolving complaints between neighbours. These instruments are deployed by housing officers within local authorities and housing associations to record and capture noise events as evidential material where a disturbance is alleged.

The systems are commonly referred to as noise nuisance recorders or noise monitoring kits. They are typically based on established sound level meter platforms such as the Norsonic Nor140 or Nor145 NNR kits and the Larson Davis 821 SoundExpert NNR kit, supplied exclusively in the United Kingdom by Campbell Associates. The abbreviation NNR has become widely adopted as a general term for this type of equipment.

Noise recordings are supported by event logs completed by the resident, which accompany each captured event. The devices log sound pressure levels in decibels to assess the impact and pattern of noise. As measurements are taken within the complainant’s property, background levels are often relatively low, meaning internal sounds may also be detected. For this reason, audio recordings are essential to assist with identifying the source of disturbance, such as dog barking, amplified music or raised voices.

With a plotted noise trace and synchronised audio recording, it is possible to visually examine changes in sound level over time and describe frequency characteristics. Low frequency content is often emphasised in frequency analysis displays when music is present, while impulsive sounds such as dog barking appear as sharp spikes in the level trace.

Modern instruments use sophisticated pre trigger technology to capture audio prior to the moment the resident presses the event trigger. This ensures that the build-up to the disturbance is recorded, even if there is a delay in activation. By the time the resident attends to the instrument and presses the trigger button, the relevant event has already been captured, thereby strengthening the evidential quality of the recording and improving reliability in reporting and investigation.

It is critical that equipment is not only technically advanced but also simple to operate. The Larson Davis 821 SoundExpert NNR kit has been developed to provide a cost-effective solution for an industry operating within tight budgets, where reliable performance is required without the expense typically associated with high specification acoustic systems.

Demand for monitoring equipment has increased since the COVID pandemic, largely due to more people working from home and becoming more aware of neighbouring noise in domestic settings.