Annual report 1998-1999

ISVR Consultancy Services

Manager Mr R A Davis

Manager's statement

ISVR Consultancy Services (ICS) is a self-funding advisory unit which carries out short- and medium-term consultancy and research for a wide range of public- and private-sector clients. The Unit operates on a commercial basis, with full-time engineering and support staff and an extensive pool of measurement equipment for site and laboratory investigations. It maintains close links with ISVR Research Groups, and manages the ISVR's main test chambers, comprising anechoic and reverberation rooms.

The Unit generated a trading surplus in 1998-99 and staff numbers have increased with the recruitment of two engineers, Reuben Peckham and Brian Dennis.

Projects are client-confidential. The following review illustrates the range of work undertaken and identifies some general technical and business trends within the consultancy activity.

Environmental noise

Many projects involve the assessment of noise from proposed industrial or leisure-related developments affecting nearby residential areas. A number of such assessments have been carried out in the vicinity of sites to be used for mineral extraction or associated uses such as asphalt manufacture, landfill or waste recycling. Other projects include the prediction and assessment of noise from night clubs, a chicken farm and a vehicle repair operation.

Other investigations are concerned with proposed new residential developments on sites close to existing noise sources. Government policy increasingly favours the development of urban 'brown field' sites for housing. These sites often present specific noise problems because of their proximity to roads, railways or noisy industry. A number of such projects have been undertaken on behalf of developers and local planning authorities. Evidence on noise has been presented at local Public Inquiries.

A number of environmental noise problems have been investigated. These most often concern industrial noise affecting residential areas at night. Many problems involve impulsive or tonal components which are often 'under-valued' (in terms of incidence of complaints) by the application of British Standard BS 4142:1997.

The Unit is advising on the noise control design of an on-shore gas compression station in Norway. A major source of environmental noise from this installation is predicted to be breakout of noise from compressors and control valves through pipe walls and from vessels. Pipe radiated noise is often important for large process works but is difficult to predict with confidence. For this project, a volume velocity transducer and associated software have been developed and supplied to the design contractor. This device permits direct measurement of noise emission from pipes and other surfaces in the presence of high levels of background noise from other sources, and provides a practicable alternative to surface vibration measurements. The system will be used to obtain data from compressors during tests at vendors' premises, and to measure pipework noise during commissioning. The information gained will enable prediction methods to be validated and enhanced.

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Structural dynamics and computational acoustics

The main activity in the area of computational acoustics has centred on two research projects associated with the continuing drive to reduce noise pollution around airports. These major long-term contracts are administered through ISVR and carried out by ICS staff seconded to the Department.

In the first project ISVR are partners in the European-funded RAIN (Reduction of Airframe and Installation Noise) project, with responsibility for producing a mathematical model of the aerodynamic noise from aircraft landing gear. This is now a significant noise source for aircraft on approach. This work has involved the reduction and analysis of noise data acquired in the DNW wind tunnel on full scale landing gear and the prediction of flyover noise data from Airbus aircraft.

The second project involves mathematical modelling of sound propagating in lined ducts in order to optimise the attenuation of aero-engine noise. This work is being done in collaboration with the ISVR Fluids and Acoustics Research Group and Rolls Royce.

Other activities include the ongoing sales and consultancy work associated with the AutoSEA software, with some significant work for DERA on shipboard noise sources which draws on ISVR's expertise developed during recent research funded by the Marine Technology Directorate. A three day introductory course on the practical applications of Statistical Energy Analysis was organised in September. It is planned to repeat this course in future years.

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Communications and electro-acoustics

A programme of experimental work was carried out for an electronics manufacturer to develop and test a new telephone handset for use by aircraft passengers. The original design required modifications to the casing around the noise-cancelling microphone, and acoustic treatment within the casing to minimise transmission from earpiece to microphone in order to meet the desired specifications.

An assessment of the public address system in a large safety-critical process building was undertaken. RASTI measurements indicated that the main cause of poor speech intelligibility was the excessive reverberation times, rather then the relatively high background noise level. The function of the building did not permit the addition of sound absorbent materials to reduce reverberation. A solution based on modifications to the loudspeaker density, coverage and positioning was devised.

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Noise at work - hearing conservation - personal injury claims

Reports have been prepared in connection with a number of personal injury claims alleging noise-induced hearing loss.

Assessments of noise exposure in connection with the Noise at Work Regulations have been carried out for a range of occupations, including foundry workers, crane drivers, motor-cyclists, police firearms instructors and air traffic controllers. The assessment of noise exposure from headsets and 'in-ear' communications devices is an expanding area of business: reliable techniques using an acoustic manikin have been developed for such assessments.

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Laboratory testing and experimental work

ICS operates and manages the main ISVR test chambers, which are in regular use for product testing and development as well as for undergraduate and postgraduate research.

High intensity testing of aerospace components is a major element of the test programme. These components include antennae for communications satellites and external stores for military aircraft. Levels of up to 165 dB can be achieved using a WAS 3000 compressed air driver unit. The flexibility of the facility will be greatly enhanced during 1999 with the installation of new air compressors.

Numerous components have been tested to determine Sound Power Levels, using reverberant or anechoic test methods. Some determinations have also been carried out on site, in some cases using sound intensity techniques. Equipment submitted for test includes cellular telephone base stations, ventilation and air-conditioning units, computer peripherals and domestic 'white goods'. In some cases, development work to reduce noise levels has been undertaken.

The reverberation chambers permit measurements of sound transmission loss of panels to be performed to BS 2750 (ISO 140) and sound absorption coefficients to BS EN 20354 (ISO 354). A number of such test have been carried out on highway noise barriers, wall and partition constructions, and acoustic ceiling materials.

Other 'ad hoc' tests include the measurement of the output levels, frequency spectrum and directivity (but not the effectiveness) of an ultrasonic cat scarer (though no cats were spotted in the test chamber during tests).

Measurements have been made at a number of sites to establish vibration environments prior to the installation of vibration-sensitive industrial and medical equipment for micro-machining, microscopy and imaging.

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Other projects

Work for the Department of Trade and Industry, to assist in setting safe noise limits for children's toys, was described in the 1997-98 Annual Report. Further support has been provided to the EN working group responsible for toy safety standards. Assistance has been provided to a local authority Trading Standards Department, to measure noise from a wide variety of sample toys in accordance with the newly published part-standard on toy safety (BS EN 71-1:1998), and to demonstrate the necessary measurement procedures to enable them to carry out their own screening measurements in future.

ICS were appointed as acoustic consultants to advise on acoustic aspects of the design of a large 'call centre' for a major financial institution. This type of building and activity presents specific acoustical problems. Relatively high 'activity' noise levels are considered desirable to maintain staff involvement, but must not compromise speech intelligibility during telephone discussions. Solutions involve some distributed absorptive treatment and careful selection of headsets and layout of work stations.

There is increasing work in the marine industry. Projects have been completed on workboats, mainly to reduce noise levels in wheelhouses, and on luxury motor yachts where low machinery noise levels in the accommodation are a design priority. Increasing use is being made of SEA techniques to predict structure-borne noise and to optimise the design of accommodation linings and structural treatments.

Contributions were made to a European Space Agency (ESA) design manual concerning the acoustic environment within manned spacecraft. This covered the control of noise from spacecraft life support systems and from experimental apparatus.

ICS has been retained to carry out investigations and to present evidence to the Bloody Sunday Inquiry, which is concerned with the events in Londonderry in 1972. Work is being carried out in conjunction with ISVR Research staff.  The main objectives are to advise on the likelihood that witnesses could have reliably identified particular types of firearms from their sounds, whether other sounds could be confused with firearms, and whether it is possible to identify particular sound signatures on the sound tracks of contemporary television news recordings. This has involved making recordings of various firearms under various conditions, characterising the sounds, and applying advanced correlation techniques to enable sound signatures to be objectively compared. The inquiry is scheduled to re-open in September 1999.

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Publicity and Information

The Unit has its own web site,  http://www.isvr.co.uk/ , which contains technical information, recent publications and other material. This site attracts regular visitors and has generated a significant number of enquiries for new work.

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Telephone 023 8059 2162 (+44 23 8059 2162 from outside the UK),
or e-mail: consultancy@isvr.co.uk