Construction noise database (phase 3): Evaluation of established measurement protocol

Executive Summary 1.1 The established method for obtaining noise emission data for the update of a database of noise from construction plant is examined. 1.2 The established measurement protocol involves the collection of plant noise measurements using a sound level meter, and the normalisation of the data to 10m. 1.3 The results of analytical and experimental investigations conclude that this measurement protocol is reasonably accurate and a practical method for the characterisation of plant sound power on-site for both stationary and dynamic activities

A procedure for the assessment of low frequency noise complaints

The development and application of a procedure for the assessment of low frequency noise (LFN) complaints are described. The development of the assessment method included laboratory tests addressing low frequency hearing threshold and the effect on acceptability of fluctuation, and field measurements complemented with interview-based questionnaires. Environmental health departments then conducted a series of six trials with genuine "live" LFN complaints to test the workability and usefulness of the procedure. The procedure includes guidance notes and a pro-forma report with step-by-step instructions. It does not provide a prescriptive indicator of nuisance but rather gives a systematic procedure to help environmental health practitioners to form their own opinion. Examples of field measurements and application of the procedure are presented. The procedure and examples are likely to be of particular interest to environmental health practitioners involved in the assessment of LFN complaints

In-situ sub-structure decoupling of resiliently coupled assemblies

The context of this paper is the increasing need for vibro-acoustic simulation across many sectors. A procedure is derived for decoupling the components of resiliently mounted assemblies. An independent characterisation of the components is obtained such that they can be mathematically recombined with other elements to form virtual assemblies or Virtual Acoustic Prototypes. Unlike standard decoupling procedures, the proposed approach does not require the assembly to be physically decoupled at any stage. It is argued that this offers significant advantages in terms of convenience and, importantly, representativeness. The boundary conditions within a physically coupled assembly are realistic by definition, which may not be the case for physically decoupled components. The procedure is validated numerically using a lumped parameter model and demonstrated experimentally through several case studies. Keywords: In-situ, measurement, experimental,free-interface, decoupling, FRF, sub-structure, structural, characterisatio

Health impacts of wind turbines

This report presents the results of a rapid, desk based analysis of peer reviewed UK and international literature from the last four years on the effects of wind turbines on human health. The review covers literature specified by the Scottish government, peer-reviewed original studies and recent peer-reviewed literature reviews. Recent original studies consist mostly of cross-sectional studies and case studies on the effects of wind turbines on local residents. All studies present evidence for annoyance due to wind turbine noise and most concur that there is evidence for sleep disturbance in the presence of wind farms but not necessarily from noise. Both results are in agreement with the effects of noise from other environmental sources. Other health effects are increasingly reported in the presence of wind turbines but the reviewed literature does not provide firm scientific evidence of a causal relationship with wind turbines or even more specifically wind turbine noise. The most widely quoted cross-sectional studies show correlations between annoyance and visual impact, economic benefit and attitude related to wind turbines. Wind turbine sound is reported to be comparatively weakly related to annoyance and inseparable from the other contributing factors. Literature on low frequency noise and infrasound (LFIS) can be categorised as reviews, sound level measurements around windfarms and discussion of mechanisms of perception and response. A Swedish review finds no evidence to support ‘wind turbine syndrome’ while another concludes that further research is required. Regarding noise measurements, there are concerns that a new generation of wind turbines will produce a sound with a spectrum shifted down in frequency. However, a study in Australia concluded that infrasound levels near windfarms were no higher than elsewhere and that higher levels in urban areas were probably due to traffic and other human activity rather than wind turbines. Some other studies found measured sound levels near wind farms to conform with a range of criteria for LFIS. Papers by Salt et al. propose that LFIS may differentially stimulate structures in the human inner ear, and may instigate health effects even when inaudible. The authors seek to build a speculative case utilising experimental data gleaned from guinea pigs and some observations on human experiences with specific pathological conditions. Based upon the documents submitted, the proposal is unproven, and would need clear data from hypothesis driven independent research in humans in order to be credible. A proposal by US consultants that motion sickness-like symptoms reported at one wind farm might be caused by acoustic excitation of the balance organs is not new and has previously been discounted as an explanation for similar reported effects not involving wind turbines. Other evidence on acoustic stimulation of the balance organs has been noted but not reviewed. Health effects from other wind turbine related sources such as shadow flicker have been reported in several studies and guidelines to be less of a problem. Careful wind farm design and operational restrictions are suggested to be sufficient to minimise the impact. The mitigation strategies have been found to vary widely internationally with some countries and federal states using fixed noise limits, others using noise limits relative to existing background levels and many like the UK using a combination of both. Set-back distances are also used internationally but have a number of disadvantages. The relevant UK guideline document ETSU-R-97 aims to provide a reasonable degree of protection to noise sensitive listeners; without unduly restricting the development of wind turbine renewable energy resources. In the international comparison the ETSU-R-97 guidelines tends to result in comparatively low noise limits although direct comparisons between fixed and relative noise limits are difficult. ETSU-R-97 has been criticised for its inconsistent implementation and relative complexity. Good practice guidelines by the Institute of Acoustics which aim to address the implementation issues are due to be published in May

On the completeness of interface descriptions and the consistency of blocked forces obtained in-situ

Blocked forces can be used to describe, independently, the operational characteristics of a vibratory source. Their use within a computational model avoids the need to represent explicitly the complex mechanisms that lead to vibratory excitation. To obtain and apply an experimental blocked force with confidence it is important that likely sources of error are known, and measures of their severity are available. In this paper we introduce the notions of completeness and consistency, and detail their role in the introduction of systematic errors in a blocked force characterisation. Their mathematical origins are described and criteria to quantify their severity are proposed; the Interface Completeness Criterion (ICC), and the Measurement Consistency Criterion (MCC). These are illustrated through numerical and experimental examples. Completeness is related to the interface description adopted in a source characterisation (i.e. the number of degrees of freedom used). The ICC represents the quality of an interface description and can be quantified from in-situ measurements, i.e without having to remove the source from its assembly. Consistency is related to the underlying dynamics shared by active and passive quantities (whether measured or modelled). The issue of consistency is more general, completeness being a special case, and so a single criterion is hard to formulate. When an inconsistency arises between the blocked force of a vibration source and its corresponding free interface frequency response function matrix, the MCC provides a quantitative indication of its severity. Importantly, many of the concepts discussed apply equally in the context of experimental dynamic sub-structuring

Annoyance due to railway vibration at different times of the day

The time of day when vibration occurs is considered as a factor influencing the human response to vibration. The aim of the present paper is to identify the times of day during which railway vibration causes the greatest annoyance, to measure the differences between annoyance responses for different time periods and to obtain estimates of the time of day penalties. This was achieved using data from case studies comprised of face-to-face interviews and internal vibration measurements (N=755). Results indicate that vibration annoyance differs with time of day and that separate time of day weights can be applied when considering exposure–response relationships from railway vibration in residential environments

UK-wide support infrastructure for low frequency noise sufferers ('LFN Network')

The project was set up to meet a need for improved treatment of Low Frequency Noise (LFN) complaints in cases where no noise source could be found. Such cases can be highly distressing for the complainant and difficult to handle by the Environmental Health Officers (EHOs) concerned and so tend to result in disproportionate use of resources. The hypothesis is that, irrespective of the (unknown) cause of the LFN perception, the perception may be lessened through application of techniques specifically adapted from the field of tinnitus and hyperacusis therapy. The aim of the project was therefore to establish, on a trial basis, a national network of treatment centres for sufferers of LFN located within the existing network of tinnitus clinics in the UK. A network of nine audiology centres was established, including eight with a good geographical spread in England and one in Scotland. A treatment protocol, specific to LFN cases, was then developed through discussions with the centres and a referral pathway was also established. Each centre made contact initially with EHOs in one or two local authorities in their vicinity to offer the service which was widened to a larger catchment area if sufficient referrals were not forthcoming. Fourteen subjects took part, eleven of which were referred from EHOs, the remaining three being self-referred. Outcome measures were based on a combination of validated questionnaires for general health, anxiety, depression, tinnitus handicap (with LFN substituted for tinnitus) and hyperacusis, combined with visual-analogue scales specifically developed for LFN to measure the pitch and loudness of the perceived LFN and the associated distress. Qualitative and open questions were also used. Potential benefits to EHOs of being able to make referrals were evaluated by semi-structured telephone interviews in which five EHOs participated. Generally, EHOs were very positive about the service and wanted it to continue. It was clear that LFN cases require significant resources which can be reduced if the referral service is available. Audiologists’ experience was evaluated in a similar way: they were generally willing to take part in the scheme and wanted it to continue and there was a feeling that they would have liked more referrals to get more experience in the use of the protocol. The results showed a mixed picture with some clients, three in particular, showing improved scores across a range of measures with little or no benefit for others and a worsening for one case. The improvement of some clients is positive given the lack of options available for this client group, however, the success of the approach can be considered partial at best. The questionnaire scores indicated that individuals taking part were significantly agitated, stressed and distressed. Those individuals with LFN complaint have a significant clinical need although in the main they were not clinically anxious or depressed. The model proposed of stress and increased auditory gain is a plausible explanation for the symptoms noted in LFN cases. In particular, the involvement of the sympathetic autonomic nervous system, and of the emotional brain, is likely to be a faithful representation of the clinical situation. A number of useful signposts for future development were derived. First, EHOs as well as audiologists should ideally receive training in best practice to help them to handle the particular sensitivities of LFN cases. More awareness and information for GPs is also recommended. A simplification of the referral route, potentially going direct to the audiologist rather than via the GP would also be beneficial. A strong argument for the continuation of the service is that some EHOs are now taking the initiative in contacting audiologists independently to refer LFN complainants in ‘No Noise Found’ cases. Without adequate training things could be made worse but access to a specific LFN protocol and associated training is likely to increase the chances of success significantly. It is recommended that existing guidance for EHOs be extended to include details of audiology services, guidelines for EHOs in making referrals and reference to the LFN treatment protocol. Using data from the study two independent estimates of the incidence rates of LFN cases can be derived. It is estimated that there are up to 160 complainants per year in the NHS corresponding to 0.32 cases per 100 thousand per year. The incidence rate based on referrals made by EHOs is 1.01 per 100 thousand per year within local authorities. It is not known to what extent, if any, these populations overlap