Method Implementation Document for BS 4142 Julija Smyrnowa 1 Environment Agency Quadrant 2, 99 Parkway Ave, Sheffield S9 4WF. UK Tony Clayton Environment Agency Lutra House, Dodd Way Off Seedlee Road Walton Summit Centre, Bamber Bridge Preston, PR5 8BX. UK Jon Tofts Environment Agency Rivers House, Bridgwater, Somerset, TA6 4YS. UK Gillian Brown Environment Agency Tyneside House, Newcastle upon Tyne NE4 7AR. UK

ABSTRACT BS 4142:2014+A1:2019 “Methods for rating and assessing industrial and commercial sound” is the standard that the Environment Agency (EA) requires to be applied for the assessment of most indus- trial sound sources. Since its publication in 2014 (in 2019 only some minor updates were introduced), it has become evident that the standard is prone to misinterpretation, particularly in relation to esti- mating uncertainty and in terms of context at which the sound occurs. As a consequence, the quality of most of noise impact assessment reports submitted to the EA has been very low. In order to improve the quality of environmental measurements and assessments of noise impact, the EA has established a Method Implementation Document (MID) for BS 4142. The MID provides de- tails on how the standard shall be used for regulatory monitoring for permit applications or for com- pliance with a permit. Where required, the MID should be used to supplement the EA’s guidance Noise and vibration management: environmental permits (that supersedes Horizontal Guidance Note H3 which has been withdrawn). However, it does not re-state all the provisions of BS 4142 and or- ganisations are reminded of the need to comply with the criteria detailed in BS 4142:2014+A1:2019.

1. INTRODUCTION

In order to regulate pollution emissions from industrial installations, the UK Environment Agency (EA) follows the methods of the Industrial Emission Directive (IED) - Directive 2010/75/EU) [1] The EA recognises that national and international standards may need to be supplemented by Method

1 julija.smyrnowa@environemnt-agency.gov.uk

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Implementation Documents (MIDs) to ensure they are being implemented consistently and in accord with the IED requirements. There are MIDs for the monitoring of emissions to air, land and water (MCERTS) and the full list of the MID documents can be found in [2].

The Environment Agency requires that BS 4142:2014+A1:2019 “Methods for rating and assessing industrial and commercial sound” [3] is used to assess the noise impact from industrial sound sources. BS 4142 details the method for determining, at the outside of a building, sound levels from industrial or commercial premises. It also specifies how the ambient, background and residual sound levels should be determined, and how these should be used to determine a rating level for the industrial or commercial sound. The rating level is used to indicate the noise impact.

Since its publication in 2014 (in 2019 only some minor updates were introduced), it has become evident that the standard is prone to misinterpretation, particularly in relation to estimating the uncer- tainty of the assessment and in terms of context in which the sound occurs. Correct interpretation of noise impact assessments does indeed requires a considerable degree of practical experience in acous- tic measurements, as well as good perception and understanding of the physics of sound propagation. As a consequence, the quality of most noise impact assessment reports submitted to the EA has been very low.

In order to improve the quality of environmental noise measurements and the assessments of noise impact, the EA has established the Method Implementation Document for BS 4142. The MID clari- fies how the standard shall be used for regulatory monitoring for permit applications or for compli- ance with a permit. Where required, the MID should be used to supplement the EA’s guidance Noise and vibration management: environmental permits ( that supersedes Horizontal Guidance Note H3, which has been withdrawn) [4]. However, it does not re-state all the provisions of BS 4142 and or- ganisations are reminded of the need to comply with the criteria detailed in BS 4142:2014+A1:2019. Organisations wishing to submit sound monitoring and assessments to the EA shall follow the re- quirements of both the standard and, where available, the MID.

At the time of writing this paper, the MID for BS 4142 is yet to be published and still to reach its final draft. . However, the EA expects that it will be officially published by late summer 2022. The MID will be freely available to the public.

2. STRUCTURE OF MID FOR BS 4142

The structure of the MID document resembles the structure of BS 4142, with corresponding section names. Where no additional clarification of the standard’s text is necessary, it simply states: “No additional requirements to BS 4142.” However, where appropriate and relevant, further clarifications to the standard are added in the corresponding section of the MID.

2.1. Remarks regarding published versions of BS 4142 The MID emphasises that BS 4142:2014+A1:2019 is a superseded version of BS 4142:2014, which is withdrawn. It also says that the BS 4142 standard was first published in 1967 but has been subject to revision and amendments in 1975, 1980, 1982, 1990 and1997, with the latest version published in 2014. The 2019 edition of the standard is a reissue of the 2014 version, with only minor changes such as stylistic and grammatical corrections.

The MID also emphasises that neither of the 2014 and 2019 editions mention assessment of sound- scape as a useful tool for demonstrating context. The MID states that soundscape should be under- stood as defined in BS ISO 12913-1 [5] as the “acoustic environment as perceived or experienced and/or understood by a person or people, in context”.

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3. THE MOST CRUCIAL ISSUES ADRESSED IN MID

In the MID, additional information clarifying the EA’s expectations is added for nearly each section of BS 4142. Some of the clarifying sections are very detailed, while the others are short and brief. It is not possible to cover the full MID within this – the readers should refer to the MID when it is published – however the most crucial issues are presented here.

3.1. Scope In terms of a noise sensitive receptor, BS 4142 defines this as residential property occupied by human receptors. The MID clarifies that it should not be used for identification of impact on non-human receptors such as bats, birds or other protected species. Similarly, it should not be directly applied for identification of noise impact on non-residential premises such as offices, schools, churches etc. or outdoor areas such as recreational parks, gardens or sports grounds. Nevertheless, if the outcomes of a noise impact assessment indicate an adverse or significantly adverse impact outside of a non-resi- dential human receptor mentioned above, it may well indicate a similar impact on those receptors depending on context.

The EA expects that BS 4142 should be used almost without exception to assess environmental noise impact from industrial or commercial processes. In very rare circumstances, other methods may also be appropriate.For example, DEFRA Procedure NANR45 [4] may be appropriate for assessing existing low frequency sound inside a residential property.

The MID further states that BS 4142 should not be used for the assessment of noise impact from vehicles or from fixed installations that are outside of the site permit boundary. For example, if a waste wagon drives to a site, while it is outside of the permit boundary, the sound is ‘road noise’ and is regulated by a local council. Once it is inside the permit boundary, it is then part of the commercial or industrial sound (under EA’s permit).

3.2. Normative references The MID lists the ISO 12913 [5-7] series of standards, which relate to the assessment of soundscape. It also adds that further parts of ISO 12913 might be published after the publication of the MID and therefore should also be referred to.

3.3. Specific sound level - general The MID clarifies that if the residual sound pressure level is less than 3dB below the measured am- bient sound pressure level, the determination of the specific sound level will be significantly influ- enced, and the measurement uncertainty will then be large. Note that the Standard’s requirement “is less than or equal” which, in the professional opinion of the EA, may lead to underestimation of the specific sound level. The EA, however, does not exclude the approach of “less than or equal” com- pletely - the results may still be reported and may be useful for determining an upper boundary to the sound pressure level of the specific source under investigation. If such data is reported, it must be clearly stated in the text of the report, as well as in graphs and tables of results, that the requirements of this test method have not been fulfilled.

The MID also clarifies that if the measured residual sound level is above the measured ambient sound level, then the measurements need to be repeated and the reason should be investigated.

3.4. Determination of the specific sound level The MID clarifies that measurements of the ambient and residual sound level at the assessment loca- tion(s) used to determine the specific sound level should be done over representative measurement duration periods, during similar meteorological conditions and during the same season.

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If pausing for e.g. passing cars or people chatting is used during the ambient sound measurements, the same pausing approach should be used during the residual sound measurements. All pausing should be justified and reported. If, for example, a specific sound source would operate only during rush hour periods and it is located next to a busy road, it would be unreasonable to pause each time a car passes the assessment location. Similarly, it would not be acceptable to pause for each passing aeroplane if the site is located under a flightpath or close to an airport. Constant sound source(s) should be considered to be a typical element of the acoustic environment.

3.5. Background sound level The MID specifically warns not to include the existing site sounds as part of the background (and residual) measurements when assessing the impact of proposed, modified or additional source(s). This includes when assessing the impact of extended hours of operation or when introducing an ad- ditional plant item. During the measurements, all site activities should be reduced to the level where they no longer contribute to the L 90,T and where they are inaudible at the measurement location.

In cases where the existing sound source(s) is operating continuously, the MID suggests encour- aging the operator to temporarily stop the source(s) operating, if possible. Otherwise, another method such as measuring at a proxy location may be applied, with full justification.

3.6. Introduction of a new sensitive receptor When introducing a new noise sensitive receptor, the MID warns that BS 8233 [8] should never be used to quantify pollution, as this method is used for the identification of sound insulation require- ments and relies on constant sounds such as from traffic or railways and does not take into account any acoustic features such as tonality, impulsivity, intermittency and other distinguishable features that are usually associated with an industrial/commercial sound source.

3.7. Rating level The MID emphasises that if a correction is applied for any acoustic features, to the acoustic feature must be audible at the receptor, not at any location closer to the source or at an artificially quieter time. The corrections should normally be applied using simple linear addition. If one acoustic char- acteristic is dominant, then it could be appropriate to only apply one correction e.g. a dropped alloy wheel hub could be both tonal and impulsive, but it would be acceptable to apply just one correction (probably the largest).

The MID also clarifies that the calculated methods for assessing acoustic features (including both objective and reference methods to assess tonality and the prominence of impulsivity) are designed to replicate what we hear in a sound under assessment. If the calculated methods do not match our observations, then it should be the observations that take priority over the calculations. The assessor should rely on the calculated methods when their observations are somehow ‘insufficient’.

3.8. Uncertainty The MID points out that with the advancement of modern sound level meters, the uncertainty caused by acoustic measurement devices is the lowest of all the possible sources of uncertainty. It further lists the uncertainties of the measured and calculated values. For the former, the MID states that if the sound power level of the specific sound source is measured, the methodology of an appropriate standard should be followed, and the calculations and measurements should be presented and fully justified. A special warning is also made with regards to measuring sound power in the near field. More details on these are presented in another paper by one of the authors of this document [9].

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3.9. Assessment of impact The MID emphasises that assessment of context is crucial for the assessment of impact from an in- dustrial and/or commercial noise source. The EA’s Noise and vibration management: environmental permits guidance provides a list of what can be included as "context". However, it is important to bear in mind that it is not an exhaustive list as there are no strict rules on what elements could make a context more or less sensitive. If the assessment outcomes are modified based on context, it is paramount that full justification is provided to support this. The MID also lists possible issues that should be considered while making decisions about context.

3.10. Annexes The MID makes no comments on the annexes in BS 4142 except for A.6.1 Example 6. That example demonstrates applicability of BS 4142 for an indoor receptor with open windows. The EA considers that theexample has several flaws as follows: (1) it assumes that the residual sound within the dwell- ing will somehow mask sound from the plant without proper justification or details of the expected level of masking; (2) it incorrectly applies a BS 8233 limit of 35dBA indoors for bedrooms at night- time instead of the correct limit value of 30dBA; and (3) it assumes that an open window will provide 10dB sound reduction from outdoor to indoor without any justification or explanation. Furthermore, the limits of sound levels set in BS 8233 relate to all external sounds entering a room from outside plus all internal sounds being transmitted though the internal partitions, and plus all internal sounds generated inside a room e.g. from a mechanical ventilation. In terms of external sounds, BS 8233 assumes constant sounds such as from traffic or railways and does not take into account any acoustic feature such as tonality, impulsivity, intermittency and other distinguishable features that are usually associated with an industrial/commercial sound source. As a consequence, the approach presented in A.6.1 Example 6 is deemed to be unsuitable for the identification of impact for an indoor receptor. 4. CONCLUSIONS

This paper presents an overview of the structure and most crucial issues addressed in the EA’s Method Implementation Document for BS 4142. It is expected that by the time of INTER-NOISE 2022 the MID will be published and ready for use by all interested parties free of charge. 5. ACKNOWLEDGEMENTS

The authors of this paper are grateful for all valuable comments they received from colleagues from other departments in the Environment Agency and also from colleagues at SEPA, NRW and NIEA. 6. REFERENCES

1. The Industrial Emissions Directive - Environment - European Commission (europa.eu) 2. Monitoring emissions to air, land and water (MCERTS) - GOV.UK (www.gov.uk) 3. BS4142: 2014+A1:2019, Method for rating and assessing industrial and commercial sound . UK

British Standards Institution, 2019. 4. “Guidance – Noise and vibration management: Environmental Permits”, July 2021. Joint guid-

ance by Environment Agency, Natural Resources Wales, Scottish Environment Protection Agency and Northern Ireland Environment Agency. 5. ISO 12913-1:2014, Acoustics — Soundscape — Part 1: Definition and conceptual framework. 6. ISO/TS 12913-2:2018, Acoustics — Soundscape — Part 2: Data collection and reporting re-

quirements .

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7. ISO/TS 12913-3:2019, Acoustics — Soundscape — Part 3: Data analysis . 8. BS 8233:2014, Guidance on sound insulation and noise reduction for buildings. British Standards

Institution, 2014. 9. Tofts, J. Error and Uncertainty in Near-Field Sound Power Assessments of Industrial Source.

Proceedings of INTER-NOISE 2022 , Glasgow, UK, August 2022.

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