Background
BMCG commissioned Anderson Acoustics to undertake a noise assessment for the redevelopment of 31 Totteridge Common, formerly the Ellern Mede Eating Disorder Hospital for Children, into a single dwelling residence.
The assessment was required to discharge planning conditions related to noise emissions from new plant installations, ensuring compliance with local authority policies and safeguarding the amenity of neighbouring residential properties.
Challenge
The primary challenge was to assess and mitigate the potential noise impact from proposed plant items (serving both the main house and a swimming pool) on nearby residential receptors, specifically 31A ‘The Lodge’ and 33 Totteridge Common.
Planning conditions stipulated strict noise limits: plant noise emissions must be at least 5 dB(A) below the background level at any neighbouring window, or 10 dB(A) lower if the noise has distinguishable tonal or impulsive characteristics.
Although located adjacent to a busy main road, this residential redevelopment was governed by unusually low night-time background noise levels, falling from 51 dB LA90 during the daytime period to around 25 dB LA90. This created a stringent constraint for plant noise, far more demanding than the daytime environment suggested.
What We Did
- Environmental Noise Survey: Conducted a continuous unattended noise survey at the site, measuring both daytime and nighttime ambient and background noise levels. Weather conditions were monitored to ensure data reliability;
- Assessment Methodology: Applied BS 4142:2014+A1:2019 standards to rate and assess the impact of industrial and commercial sound on residential premises. Calculations considered worst-case scenarios, including plant operating at 100% duty and outdoor temperatures of 7°C;
- Noise Predictions: Used manufacturer data for a representative unit (Mitsubishi CAHV-R450YA-HPB) to predict sound pressure levels at the nearest residential windows, factoring in distance, screening effects (fences and foliage), and building envelope attenuation for indoor pool plant items;
- Mitigation Strategy: Early-stage modelling, undertaken before plant selection was finalised, revealed a clear divergence in target criteria:
- while plant noise at nearby residential properties complied with planning requirements during the day, it significantly exceeded night-time limits. This indicated that the issue was not excessive plant noise in isolation, but its interaction with a highly sensitive night-time acoustic environment.
- by isolating the dominant source – the main house plant – and discounting lesser contributors such as the enclosed plant serving the pool, the assessment enabled a targeted mitigation strategy. An acoustic enclosure targeting the most prominent noise source, and providing an insertion loss of at least 16 dB, reduced overall plant noise levels at nearby residences to within acceptable limits and enabled compliance with planning conditions.
Result
- Compliance Achieved: With the recommended mitigation, predicted cumulative sound pressure levels at the nearest residential windows were reduced to 30 dBA during both daytime and nighttime periods, meeting the design criteria set by the local authority;
- Low Risk of Adverse Impact: The assessment concluded a low risk of adverse noise impact on neighboring properties, subject to the implementation of the proposed acoustic mitigation measures;
- Planning Conditions Satisfied: Our approach transformed a potential planning constraint into a defined and deliverable design solution, supporting the progression of the development. On 24th July 2025, Barnet London Borough Council approved condition 7 (Noise) and 8 (Noise Report).
