Annual report 1994-1995
|Every year the Institute of Sound and
Vibration Research publishes its Annual Report. These are the chapters on ISVR Consultancy Services
Automotive Design Advisory Unit for
the year May 1994 - April 1995.
ISVR Consultancy Services
Manager Mr R A Davis
The year has seen a steady growth in business opportunities and enquiries for consultancy services. Strong competition, particularly from small private companies, is evident in many of the 'traditional' business areas, such as environmental noise surveys and workplace noise assessments. This is accepted as a natural development of the consultancy market; the Unit's policy is to continue to offer a diverse range of services, whilst focusing on generating business in high-technology areas, where the Unit can take full advantage of the support available from within Research Groups, and the availability of excellent experimental facilities.
The formation of closer links between the consultancy unit and research groups remains a fundamental objective. A significant development has been the appointment of Dr Neil Ferguson to a newly-founded Industrial Lecturer post; Dr Ferguson combines teaching and research activities with consultancy in structural dynamics. Malcolm Smith, a senior consultant in the Unit, has undertaken an additional role, to establish a forum to identify technical areas where current research interests can be directed into consultancy, and industrial problems referred to Research Groups. Such interaction has always been a feature of the operation of the ISVR consultancy units, but it is recognized that a new initiative is now required to enhance this essential activity.
A memorable occasion in September 1994 was the (formal) retirement of Ken Ratcliffe, after over 21 years with the Unit, latterly as its Deputy Manager. Ken has gained a national reputation in the area of environmental noise and planning, and regularly presents evidence in Court and at Public Inquiries. We are delighted that he is continuing to work in the Unit on a part-time basis.
The Unit generated an operating surplus in the 1993-94 financial year, and satisfactory financial results are anticipated for 1994-95.
Summary of Activities
The Unit's projects are client-confidential, but the following general descriptions illustrate the wide range of work being undertaken.
Environmental noise and vibration
This area of work continues to expand steadily. A large number of projects involve the assessment of the noise impact of proposed developments, including mineral extraction operations and wind farms. The steady recovery of the housing market, and the publication of the new Planning Circular PPG24, has led to regular enquiries for the assessment of proposed housing sites exposed to road and rail noise and vibration.
There has been a marked increase in the number of problems of inadequate sound insulation between recently-constructed dwellings, apparently as a result of increased public awareness of neighbourhood noise, together with unsatisfactory attention to detail during construction. ICS has undertaken a number of detailed surveys, mainly on behalf of Housing Associations, and has designed effective and practicable schemes of remedial works.
The Unit has assisted Local Authorities, owners of premises, and private individuals in cases of alleged noise and vibration nuisance. Many of the problems appear to stem from manufacturing companies extending their working hours to increase production, after having reduced capacity during the recession. Premises investigated include a petrol filling station, a stonemason's workshop, two iron foundries, a drop-forge and a number of night clubs and public houses.
Projects in the water industry include the appraisal of the design of a 5 MW standby power generation plant in a residential area, and an assessment of noise and ground vibration from machinery and from turbulent water flows over cascades and weirs in a large underground waste-water pumping station close to housing.
Transportation noise projects include further surveys of noise on the routes of the Sheffield Supertram, which is now in service, and a theoretical and experimental investigation into noise radiated from elevated structures on the Docklands Light Railway, undertaken in collaboration with the Structural Dynamics Group.
Measurements have also been made on a new design of hovercraft, and of a car ferry operating on a river crossing in the Irish Republic, causing complaints from residents. A major investigation has been carried out, involving field surveys near a major UK airport, to assess the effectiveness of different types of glazing in protecting dwellings against aircraft noise. The Unit is advising the UK Association of Motor Racing Circuit Owners and the RAC Motor Sports Association on the production of a draft Code of Practice on controlling noise from motor sports.
Laboratory testing product development and measurement services
The Unit operates and manages a suite of laboratories, comprising two large reverberation chambers and a large anechoic chamber, together with extensive instrumentation for laboratory and site use.
A significant proportion of test work involves high-intensity acoustic fatigue testing of aerospace components. The ISVR facilities, using compressed-air driver units, are unique in the UK. Tests have been carried out on a number of large (up to 3 m diameter) antenna dishes for INMARSAT satellites, with test levels up to 150 dB. Work is in hand to modify the test arrangement to enable additional driver units to be installed, to enable higher levels and improved control of the test spectrum to be achieved.
A number of laboratory and site tests have been carried out to determine equipment sound power levels in accordance with the ISO 3740 series. Test items include cellular telephone base stations, cooking ovens for fast-food establishments and aircraft, and various items of machinery for which suppliers require noise data to comply with the EC Machinery Directive (89/392/EEC). In some cases, the client has commissioned additional investigations to identify noise sources and develop methods of noise reduction.
Several laboratory measurements have been made to determine the Sound Reduction Index of composite panels and of more conventional construction materials, as well as measurements of sound absorption characteristics of 'acoustic' blocks and concert hall seats, and the acoustic insertion loss of glass fibre and polyurethane foam linings to sheet metal ductwork for ventilation systems.
The Unit is collaborating in a DTI-funded project to develop a novel form of air-conditioning unit for application to rail vehicles, with the objective of reducing noise levels within and outside the vehicle.
Laboratory and field tests are in progress to design and develop a new form of microphone windscreen, to provide improved attenuation of wind-induced noise and so enable reliable outdoor noise measurements to be made in wind speeds in excess of 3 m/s. This is a particular requirement in wind-turbine noise studies.
A major refurbishment of the ISVR test chambers, including the re-lining of the large anechoic chamber, is planned for late 1995. These developments will extend the Unit's capabilities. A draft Quality Manual has been produced to support the Unit's application for NAMAS accreditation, which is progressing satisfactorily.
Workplace noise hearing protection and noise-induced deafness
The Unit is regularly commissioned to carry out assessments of noise exposure in cases of alleged noise-induced hearing loss, on behalf of plaintiffs and defendants, and staff have presented evidence in Court on a number of occasions. A growing number of cases involve alleged injury from noise produced by communications headsets. In such investigations, a head-and-torso simulator (KEMAR manikin) is used to enable noise exposure measurements made at the ear to be reliably converted to the equivalent free-field values.
A major project has been undertaken for an international airline to assess the noise exposure of flight crews on long-haul flights. The KEMAR manikin has travelled over 20,000 miles in the observer's seat on the flight deck of a range of aircraft types, wearing a communications headset, with an ICS engineer in attendance.
Assessments of noise exposure have been made for military personnel using an audiovisual battlefield simulator, as well as for staff in more conventional workplaces, including breweries, nightclubs and a national broadcasting studio. Work has continued for the Home Office Scientific Development Branch to investigate means of reducing the noise exposure of police motorcyclists.
Close liaison is maintained with audiological scientists in the Human Sciences Research Group.
Analytical modelling and structural dynamics
The Unit is continuing to work with Research Groups in the development of statistical energy analysis (SEA) techniques to predict noise and vibration transmission in complex structures. ICS is the UK agent for the AutoSEA software package. A project is in progress for the European Space Agency to identify possible non-space-related applications for SEA techniques, which have been developed for spacecraft vibro-acoustic predictions. Further pilot projects are in hand, funded by the DTI and a consortium of industrial companies, to apply SEA to study vibration transmission through ship hulls and superstructures, and in offshore structures.
In the automotive field, SEA has particular applications in the design of car bodyshells and trim to control interior noise. Major contracts are under way for UK and European manufacturers to produce SEA models of complete bodyshells, or large sub-assemblies, to form a basis for optimization studies. This work is being carried out in collaboration with the Structural Dynamics and Automotive Engineering Groups.
Two projects are in progress with aircraft companies to investigate noise in passenger cabins of turbo-propeller aircraft, and to reduce internal noise by optimizing cabin trims and furnishing, together with, in one case, the use of an active noise reduction system.
Electroacoustics, communications and warning sounds
The Unit is involved in a number of long-term projects related to speech intelligibility, in collaboration with DRA Farnborough and DRA Malvern.
Following previous projects, a further design has been developed for an in-flight entertainment system for a large VIP jet aircraft. The working system was demonstrated to the client's representatives in a full-scale cabin mock-up.
A technique has been developed for the assessment of PA system intelligibility in helicopter passenger cabins, on the basis of measurements made in a number of Super Puma aircraft serving offshore installations from Aberdeen.
Lower, M.C., Hurst, D.W., Claughton, A.R. and Thomas, A. Sources and levels of noise under motorcyclists' helmets. Proceedings of the Institute of Acoustics, 16(2), 1994, 319-326.
Pinder, J.N. Tests of a robust acoustic absorber material for application in an industrial hygienic environment. Proceedings of the Institute of Acoustics, 16(2), 1994, 403-411.
Ratcliffe, K. Windfarm developments. Acoustics Bulletin, 19(5), 1994, 29-30.
Automotive Design Advisory Unit
Manager: Mr J D Dixon
As the automotive industry continues to climb out of recession, so the number of enquiries has risen. Many past clients have returned to discuss collaboration after a period of absence, whilst new client contacts have increased significantly. This clear increase in potential work has allowed the Unit to consider a limited expansion. Andrew Varley joined the Unit from the Auto-motive Engineering Group and his arrival has greatly benefited the analytical team.
The bias of the work has changed slightly, with an increase in projects on both large truck power units as well as small two-wheeled vehicles.
A new area of activity is that of collaboration with other major Automotive consultants. The former reluctance to work with competitors has been largely overcome, and it is believed that forms of joint project are likely to be seen increasingly throughout the industry in future years.
A small expansion in space at the Chilworth facility will allow the commissioning of a new vehicle laboratory, outline plans for which are being drawn up.
Healthy trading figures were achieved, showing a modest increase in turnover on last year with a slightly reduced running expenditure. Firm orders of substantial value give promise of yet another successful year ahead.
Summary of Services Provided
With their excellent low-frequency acoustic performance, the two free-field chassis dynamometers continue to be in heavy demand for the development of intake and exhaust systems. By using these facilities in conjunction with analytical packages developed by the Fluid Dynamics and Acoustics Group, the Unit is able to supply a comprehensive intake and exhaust design service for both orifice and shell noise.
A number of projects have recently been undertaken using sophisticated rotating shaft instrumentation. The usual focus for such work is at either end of the engine, with flywheel dynamic studies being driven by noise quality issues and front-end drive studies being required for solving durability problems. Much of the instrumentation has been developed in-house, from the dedicated transducers to the decoding electronics.
Measurement techniques to support the simulated contribution analysis have continued, with tyre noise measurement and simulation proving the most challenging. The concept of supplier targets for tyre noise provides a number of development hurdles owing to the heavy dependence of tyre noise on road surface.
Design and manufacture
The demand for Engine Noise Simulators (ENS) continues with a further two designs being developed and manufactured. Two Tailpipe and Intake Noise Simulators (TINS) have also been supplied to customers in the USA and Germany.
An increasing number of clients are using the structural design optimization expertise of the Unit. Both 'blue sky' design projects as well as the updating of existing designs have been carried out over the past year.
A major design optimization recently carried through to the prototype hardware stage was evaluated experimentally by the Unit. Correlation between the analytical and experimental studies was most favourable, thus instilling further confidence in the numerical approach.
The Unit participated in a number of Departmental activities including lecturing on short courses, both internal and external, organized by the Automotive Engineering Group. Unit engineers also provided lectures and project supervision for MSc courses.
Baker, J.M., Bazeley, G., Harding, R., Hutton, D.N. and Needham, P. Refinement benefits of engine ancillary dampers. Proceedings of the Institution of Mechanical Engineers International Conference on Vehicle NVH and Refinement, Birmingham, 1994, 149-158.
Dixon, J., Rhodes, D. and Phillips, A.V. The generation of engine half orders by structural deformation. Proceedings of the Institution of Mechanical Engineers International Conference on Vehicle NVH and Refinement, Birmingham, 1994, 9-17.
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