Background
UPP commissioned Anderson Acoustics to conduct a noise impact assessment for the conversion of a commercial property into four residential units at 183-187 High Street, Bromley. The assessment was required to satisfy two planning conditions related to noise, ensuring the new homes would provide a comfortable and compliant living environment.
Challenge
The site is located directly on Bromley High Street, with a bus stop in front and significant road traffic as the dominant noise source. The main challenges were:
- High external noise levels, especially at night, due to traffic;
- The need to meet internal and external noise criteria set by local planning conditions and British Standards;
- Ensuring effective sound insulation between the new residential units and retained commercial spaces.
What We Did
Baseline Noise Survey
A detailed environmental noise survey was conducted over several days to measure existing noise levels at the site. Measurements were taken at the first-floor façade, capturing both daytime and night-time conditions.
Acoustic Modelling & Assessment
A 3D noise model was developed to predict noise levels at each proposed dwelling’s façade. The model was calibrated using the measured data to ensure accuracy.
Internal Noise Mitigation
- For most units, it was determined that internal noise standards could be met with open windows, allowing for natural ventilation;
- For one unit, due to higher noise exposure, an alternative ventilation strategy was recommended: a Mechanical Ventilation with Heat Recovery (MVHR) system with a cooling module, and enhanced double glazing.
Sound Insulation Design
- Detailed specifications were provided for upgrading separating floors and walls between commercial and residential areas, including mineral wool infill, acoustic plasterboard, and independent wall linings;
- These measures were designed to achieve the required sound insulation performance
External Amenity Assessment
- Noise levels in external amenity areas were assessed and found to meet the upper guideline value of 55 dB LAeq,T, meaning no additional mitigation was required.
Result
- Compliance Achieved: All planning conditions relating to noise (internal and external) were satisfied, subject to the implementation of the recommended measures;
- Comfortable Living Environment: The proposed design ensures that future residents will enjoy appropriate internal noise levels, with effective ventilation and sound insulation;
- No Additional Mitigation Needed for Amenity Areas: Outdoor spaces meet the required standards, supporting resident wellbeing;
- Clear Guidance for Construction: Our assessment provided actionable, detailed specifications for contractors to follow, ensuring compliance and quality.
Project Progress
The Council of the London Borough of Bromley approved details pursuant to planning conditions 4 (Acoustic Assessment) and 5 (Noise Condition) on 11th September 2025.
