The Importance Of Using Qualified Acousticians
18 Oct 2022
The Delta-Simons Limited Acoustics Team routinely undertakes assessment of noise and vibration impacts for our Clients, as required by National Planning Policy Guidance and Environmental Impact Assessment legislation. This is done using appropriate assessment methodologies and guidance, and in a timely manner. Engaging with a suitably qualified and experienced acoustics professional at an early stage of a project allows risks to be identified and mitigated through design rather than relying on, for example, acoustic barriers or restrictions to operating times.
For example, say a developer wants to construct a logistics and distribution hub adjacent to an existing residential development, and comes to us after all design work has been undertaken because the local planning authority has requested a noise impact assessment as the proposed loading bays face directly towards the residential development. In this situation, the options for mitigating any potential noise impacts are limited, and any mitigation we may propose could have impacts on other disciplines. This may cause delays to the project and potentially costly redesigns of the overall layout. If we were engaged earlier in the design of the project, we could have advised on-site layout to minimise potential impacts, and therefore reduce delays and abortive works for other disciplines.
According to ‘State of the environment: health, people and the environment’ (Environment Agency, 2021), noise is second only to air pollution as a cause of pollution-related disease, yet the assessment of noise is quite often viewed as an ‘add-on’. Principal Acoustician Dan Boote provides insight, including case studies, as to why the appointment of qualified acousticians at a suitable time helps to mitigate risks to projects.
The Importance Of Using Qualified Acousticians
Acoustics is a specialist scientific discipline. Many aspects of the assessment methodologies we use routinely involve complex formulae, sophisticated instrumentation and computer modelling. We also need excellent communication skills to be able to interpret and explain our assessments to people without a technical background.
There are two main professional bodies for acoustics in the UK; the Institute of Acoustics (IOA) for individuals, and the Association of Noise Consultants (ANC) for companies. Both organisations contribute to the development of legislation and assessment methodologies regarding acoustics. Membership in each organisation can be obtained through demonstration of competence and experience.
Within the last few months, the Delta-Simons Limited Acoustics Team has been instructed to undertake assessments for a number of projects where the acoustic assessments for previous phases have been completed by other parties. This is not anything particularly unusual, however, there have been a few projects where the previous assessments had been carried out by people with little to no relevant experience or qualifications.
Below are two project case studies that highlight the need to appoint appropriately qualified and experienced professional acoustic consultants.
Outline Planning Consent At Risk Due To Unqualified Acoustician
One project we have worked on had already received outline planning consent. The site in question involved the redevelopment of disused barns for a residential development. At the outline planning stage, an acoustic assessment was undertaken by an unnamed individual or consultancy. However, there are a number of indicators within the report that suggest the author does not have the technical experience or qualifications to undertake a robust assessment. The application was granted outline planning permission, subject to a number of conditions, including one requiring a noise assessment.
To start on a positive note, the author referenced the typical legislation and guidance documents that were applicable at the time the assessment was undertaken. The text for each document referenced was well laid out and contained all of the salient information that should be used in the assessment, suggesting the author has a degree of understanding about the assessment process. However, the text for these sections is fairly similar for most consultancies and can be found relatively easily on planning portals where an acoustic assessment has been undertaken.
The key indicators that the author was not competent to undertake the assessment are in the noise survey and assessment sections of the report. For a noise survey, a professional consultant will use a class 1 or class 2 sound level meter, as defined in BS EN 61672, that is periodically calibrated in a laboratory, and field calibrated before and after measurements using a class 1 or class 2 sound calibrator, as defined in BS EN IEC 60942. The sound level meter used for the acoustic assessment for the outline application does not conform to class 1 or class 2 and there was no mention of either laboratory or field calibration. The meter used does not store measured levels at intervals during each measurement (known as time history), but rather records the minimum and maximum sound pressure levels over the measurement period. These levels are presented within the report, along with an average level. In acoustics, we typically use the Leq metric at some point in most assessments. This metric is sometimes (incorrectly) referred to as an average, but is more accurately an “equivalent” level over a given time period. It is calculated by taking the logarithmic average of the sound pressure levels over the time period in question, and this is a fairly basic principle that any professional will learn early in their acoustics education or career. The average levels presented in the report are an arithmetic mean of the minimum and maximum levels. This suggests that the author does not have a basic level of understanding regarding the measurement and calculation of noise indices.
The assessment section of the report is typically where a professional would take measured or modelled noise levels and perform some kind of analysis following relevant guidance and standards, and, where necessary, suggest mitigation measures to reduce noise impacts. For a residential scheme, such as this, we’d normally expect the assessment section to calculate the noise levels in habitable rooms of proposed dwellings, and where necessary, provide specifications for glazing and ventilation in terms of acoustic performance. The assessment section of the report simply states that internal noise levels should meet criteria set out in a standard. Whilst this is what we would normally try to achieve, there was no detail regarding the specification required.
For the full planning application, the client employed Delta-Simons to produce an acoustic assessment. For this, we undertook a new baseline survey using a class 1 sound level meter and calibrator and provided full specification for glazing and alternative ventilation in terms of acoustic performance. Whilst the project was not the most complicated we have undertaken, engaging with us earlier would have likely negated the need for a second acoustic assessment to be undertaken.
Residential Development Project Negates Acoustic Assessment
There is another project that Delta-Simons was not involved in, but that garnered some national media attention in early 2021. The project was a residential development adjacent to a major A road, which, in itself, is not uncommon. The project got attention due to a resident complaining about noise from the road.
Looking at the original planning application for the Site, there are a few generic comments along the lines of “soft landscaping and acoustic barrier on the boundary would reduce noise levels at the properties” in the Planning Statement and the Design and Access Statement (both based on an older site layout plan), but no evidence that a full acoustic assessment was undertaken. Permission was granted for the project, subject to a number of planning conditions; two of which were relevant to noise. One of the conditions required submission and approval of a Construction Method and Management Statement to include “measures to minimise disturbance due to noise”, and the other required a noise assessment to be undertaken, before the development commenced, that detailed any mitigation measures to reduce noise levels. A professional acoustic consultant would see these planning conditions and immediately know the scope of works required to discharge them.
Subsequently, a discharge of conditions application was submitted. To discharge the condition regarding construction, a letter was sent to the local planning authority containing the line “It is not envisaged that any onerous dust or noise will be produced.”, followed up with a note about consultations with surrounding sensitive receptors regarding larger construction operations. Granted, this was a small residential scheme adjacent to an A road, and therefore construction impacts are not likely to be significant, however, there is no evidence that due consideration was given to noise and vibration impacts during the construction period. Whilst it would make our jobs as professional acoustic consultants easier to be able to say “We don’t think noise is an issue on this Site” for every project we have, this goes against the code of conduct and ethics we sign up to as members of a professional acoustic organisation. Having a professional acoustic consultant on board to properly calculate the impacts of construction activities and advise on mitigation measures would have reduced the risk for the project.
To discharge the condition regarding mitigation for noise levels, the submitted documentation, according to the planning officer’s report, was a letter from the glazing company appointed to the project, and a glazing product leaflet. It should be noted that the letter mentioned is not available on the relevant authority’s planning portal, however, there is an image from the glazing leaflet in the planning officer’s report; this just shows the build-up of a single pane of glass for the product recommended by the glazing suppliers. To their credit, they did recommend an acoustic glazing product, which, in the location in question, is likely to be what is needed. However, the resultant noise levels within habitable rooms are dependent on a number of factors, including:
- External noise levels;
- Room dimensions;
- Façade build-up;
- Roof construction;
- Glazing dimensions; and
- Alternative ventilation (if required)
There is no evidence that a noise survey was undertaken for the Site, which means it is difficult to determine if the recommended product will sufficiently reduce noise levels to achieve internal criteria.
Regardless of the glazing specification, no consideration was given to noise levels in garden spaces; which, for some plots on the development, are directly adjacent to the road. The World Health Organization Guidelines for Community Noise set levels at which the majority of the population would be moderately or seriously annoyed. Whilst these levels are not fully achievable in all situations, there are still measures that can be taken to minimise the noise levels that future residents would be exposed to. Although the Planning Statement and Design and Access Statement for the original application stated acoustic fencing would be used, a review of online imagery shows that acoustic fencing was not installed. This has left residents with little to no acoustic protection from noise associated with the road.
Following the news articles, questions were raised about why the resident didn’t think it would be noisy living next to an A road. Whilst this is a valid question, a more important question would be why the developers would not think that noise would be an essential issue, and why the local planning authority allowed the development to proceed without an adequate assessment being done of the acoustic impacts.
The case studies above highlight the importance of appointing a suitably qualified professional acoustic consultant. Whilst it may be possible in some instances to get through the planning process without due care and attention to acoustic impacts, this approach has inherent risks that may either delay the determination of the application or result in complaints and legal procedures further down the line.
Delta-Simons has extensive experience in undertaking acoustic assessments for a wide range of projects, including residential, commercial, education, industrial and highways-related developments.
Engaging with a nationally (and internationally) trusted provider of Acoustic Consultancy services will help you reduce planning risks, identify challenges relating to noise and vibration impacts associated with your development and overall, and reduce delays when submitting applications through the local planning process.
For further information about our Acoustic services, please contact Dan Boote and our Acoustics team by emailing firstname.lastname@example.org.
About The Author
Principal Acoustician Dan Boote is a skilled acoustician and corporate member of the Institute of Acoustics with over 10 years assessing noise and vibration in the transportation, construction, education, commercial and energy sectors.
Dan's main area of expertise is in environmental acoustics and noise control, focussing on the impacts of road, rail and commercial noise sources on existing and proposed sensitive receptors. He seeks out and develops new and more efficient ways of processing data and undertaking assessments to reduce project turnaround time.
Dan has a strong technical focus, ensuring that the most appropriate methodologies and techniques are used on every project.
Linkedin: Dan Boote