Annual report 2002-2003
|Every year the Institute of Sound and
Vibration Research publishes an Annual Report. This is the
entry for ISVR Consulting covering the year May
2002 - April 2003.
Manager: Mr S J C Dyne
ISVR Consulting is a self-funding advisory unit, which carries out short and medium term consultancy and applied research projects for a wide range of clients in the public and private sectors. The unit was formed on 1 January 2003 by the merger of the two existing consultancy units, ISVR Consultancy Services and the Automotive Design Advisory Unit (ADAU). These two units have both been providing consultancy and advice for over 30 years.
John Dixon is Technical Manager for projects in automotive and marine, Malcolm Smith is Technical Manager for projects in modelling and design, and Dave Rawlinson is Technical Manager for projects in environmental noise and vibration and in laboratory services. Stuart Dyne is Manager and supervises projects in shock, forensics, hearing and electroacoustics.
The Unit operates on a commercial basis, with full-time engineering and support staff, and is a Founder Member of the Association of Noise Consultants (ANC). The Unit maintains close links with the ISVR Research Groups, and a number of projects are undertaken in collaboration with academic and research staff. The Unit website at www.isvr.co.uk includes details of the full range of services and facilities available.
As part of the merging of departmental consultancy activities, two long serving members of the ADAU have been relocated to the main campus. Nigel Davies has returned to the Tizard Electronics and Electrical Services Laboratory whilst Glen Barber has moved to the acoustic chambers in Building 15. David Pitcaithley, who had been responsible for a significant proportion of laboratory testing has retired on health grounds. We all wish Dave a long and happy retirement.
Summary of Activities
Consultancy projects are client-confidential. However, the following outline descriptions of projects in progress during 2002-03 illustrate the range of work undertaken and the general direction of consultancy activities.
During the period there were nearly 300 enquiries logged, with over 200 becoming actual projects.
The requirement for environmental assessments and advice on environmental noise control continues to be in demand. This year saw the completion of the project providing technical support for the New Forest District Council in their opposition to the proposed Dibden Bay Container Port. This led to Unit staff acting as Expert Witnesses at the Inquiry. Other projects have concerned such diverse subjects as mineral extraction, waste collection and recycling centres, a clay target shooting club, and fan noise from a foundry.
Complaints of poor sound insulation in multi-occupancy buildings have continued to yield a steady number of enquiries; these are set to increase with the publication of the revised Building Regulations. Enquiries come from both residential properties and from businesses which share buildings with residential accommodation. A related problem concerned the potential for infringement of speech privacy of a witness at a police station which led to sound insulation and speech intelligibility testing, and may require Expert Witness in court. The Unit is seeking to become approved for Building Regulations 'Schedule E' testing through its affiliation with the Association of Noise Consultants..
Test and Experimental Work
ISVR Consulting operates and manages the ISVR acoustic chambers, including the large anechoic chamber, which is increasingly used for product testing as well as for undergraduate and postgraduate research. This year the laboratory received a long awaited refurbishment which has not only made for a better working environment for the staff but projects a more professional image to clients. Considerable effort has also been made to improve to the laboratory internal Quality System.
High intensity testing of aerospace components continues to account for a large proportion of our test work.
Consideration is being given to the feasibility of increasing the maximum levels generated and of extending the low frequency capability of the facility. We feel certain that this will provide a further attraction to the aerospace industry in this demanding area. Laboratory tests to determine sound power levels have been performed on a wide range of equipment including shipboard machinery, computer peripherals, air-conditioning units, cellular telephone base stations and domestic 'white goods' , using reverberant and hemi-anechoic test methods.
Industrial sponsorship of the refurbishment of the blast wave generator has enabled this project to support a PhD student working under the joint supervision of the Unit and the Dynamics Group. The system produces a blast wave when a diaphragm bursts separating a region of high pressure (up to 200 bar) from atmospheric pressure.
The conical design of the generator is such that the resulting blast wave resembles the shock wave produced by plastic explosives in free-field conditions and will enable us to study the properties of structures subjected to airblast.
In addition to the public inquiry activity referred to above, a number of investigations have been carried out to prepare evidence in connection with criminal cases, where questions were raised about 'ear witness' testimony or the ability of witnesses to hear or recognise specific sounds. In one case, RASTI measurements were made to determine the likelihood that a suspect would have been able to hear instructions from a police officer.
In many other cases the unit has undertaken analysis of recordings made during alleged criminal activity, often with the aim of enhancing the audibility of recorded events or speech, and frequently involving the preparation of written transcripts. Following the production of a transcript of a taped conversation one of our consultants attended Bristol Crown Court, but was not called to give evidence when the accused pleaded guilty to a charge of conspiracy to contaminate the products of a cider manufacturer with intent to cause economic loss. Audio enhancement and transcription work has also been carried out in civil cases under instructions from solicitors, increasingly as a 'joint expert' representing both sides in a case.
Other litigation involves personal injury claims, and is covered below.
Noise at Work, Communications, Hearing Conservation and Personal Injury Claims
Many noise surveys were carried out to ensure compliance with the Noise at Work Regulations 1989. The various clients were engaged in production of plastic cards (such as payment cards or store loyalty cards), general woodworking, and fabrication of garden conservatories.
The year also saw continued interest in assessing noise levels from headsets and earpieces. Among the headsets and earphones tested for compliance with the Noise at Work Regulations were headsets at three call centres; covert and overt radio earpieces for a police service and three equipment manufacturers wishing to supply the police; earpieces used with new TETRA (Trans European Trunked Radio) handsets for police use; a combined waterproof earmuff and radio-intercom system onboard a lifeboat; and headphones used with sound cards in both IBM-compatible and Macintosh Personal Computers for a broadcasting organisation.
A full audit of noise from headphones and earpieces was carried out for a police force in central England. The assessment included noise levels from headsets in two control rooms; headsets in the call handling centre for general telephone enquiries; headsets in an incident room; stethoscope headsets used by audio typists transcribing taped interviews; radio earpieces as used by the firearms team, dog handlers and officers on the beat; covert wireless inductive earpieces; under flying helmets at the ears of crew members in the Air Support Unit' s helicopter; and at the ears of a uniformed motorcyclist riding a motorcycle in police livery and at the ears of an undercover officer using an unmarked police motorcycle on a simulated surveillance travelling at speeds reaching 130 mph.
Some of these measurements were carried out using a manikin or Head and Torso Simulator. Other measurements were made using miniature microphones at the ears of human subjects. Noise levels from the earphones of a number of toy cassette players were assessed for compliance with the BS EN 71-1 standard on toy safety. Headsets were also assessed to assist in personal injury claims. These included a case of alleged hearing damage from a headset used in a police control room, and a case of alleged hearing damage from tones generated when replaying taped interviews to produce transcripts.
A major investigation was carried out into the noise levels produced by loudhailers (generating speech, feedback and built-in electronic alarm sounds), compressed gas horns, whistles, and other noise-making devices which are often used in public demonstrations and protests. The project was carried out for a police force concerned about the noise levels from such devices at close range and the possibility of hearing damage or intimidation of officers policing these events. One type of compressed gas horn was capable of generating peak noise levels in excess of 140 dB and time-average levels of 126 dB(A) Leq at 1 metre: although the manufacturer advertised this product for use at sporting events, we considered it dangerous for use in crowds or at protests.
ISVR Consulting is working in partnership with the National Physical Laboratory on a project for the Department of Trade and Industry. The collaborative project, which runs from November 2002 to October 2004, deals with ear simulators, head-and-torso simulators, and hearing aid testing. The first stage of work by ISVR Consulting is to conduct an authoritative study on the relative technical and practical merits of the acoustic coupler and artificial ear used in the calibration of earphones for air-conduction audiometry. Both of these devices have been specified by the International Electrotechnical Commission, but use of the coupler is restricted to two older earphone patterns in use internationally. If the acoustic coupler could be withdrawn from use in favour of the standardised ear simulator, parallel specification of audiometric zero values would cease, and all new earphone patterns could be tested on a single device designed to mimic the acoustic properties of the human ear.
Vibroacoustics and Modelling
The principal client for modelling and vibroacoustics activity this year has been the aircraft industry. Not only have the EU SILENCE(R) project and the Rolls-Royce UTC continued to provide a steady flow of research work, but there have also been several significant consultancy projects working directly for the aircraft industry.
In particular, the year started with a major project on the design of a noise control feature for aircraft interiors and is coming to a close with a large project on design of electronic boxes to withstand high intensity aircraft noise.
The latter will, in the coming two years, lead to a large amount of testing work for the laboratory.
This year has also seen a very useful increase in activity in the area of design for low noise or for low vibration on other types of machines. For example two projects on printing machinery (at opposite ends of the technology scale) provide excellent examples of the type of business that the Unit should be developing, with a combination of modelling, experimental validation and prediction. Not only have such projects provided interesting work for our new junior staff, they have also provided opportunities for collaboration between members of the former ISVR Consultancy Services and Automotive Design Advisory Unit. These types of project will in future help consolidate the combined Consulting Unit, and will provide a useful foundation for the development of our finite element modelling and modal analysis capabilities.
The year overall has not been a completely easy ride however, with enquiries from UK business being extremely slow to convert to actual project, and being very competitive on price with a consequential drop in the success rate of proposals. Projects specifically requiring Statistical Energy Analysis have also been virtually absent this year, although there are enquiries in the pipeline, and ongoing plans to run courses.
Automotive and Marine
Trading is still difficult with research budgets in the automotive industry remaining low. Enquiry levels are still high but conversion into projects is taking increasing time and effort. An unfortunate emerging trend is for some enquiries to be no more than a means of seeking free advice with no business potential.
A number of recent test chamber benchmarking exercises for customer engines have been carried out. These demonstrated that the ISVR database approach for engine noise comparison continues to be a robust and helpful way to understand the noise performance of an engine. Engines tested this year still closely fit the noise relationships developed in the early 1990s, with any real noise reductions (or increases) being explained by the simple parametric models.
Other running engine activities have either focused on the validation of the ongoing development of hybrid modelling techniques, or on the characterisation of the noise and/or vibration of specific powertrain components.
One such component is the turbocharger and this continues to be studied in great depth. The three main turbocharger noise problems (sub-synchronous, once-per-revolution and blade-pass) appear to be cyclically studied with the main effort this year returning to compressor blade-pass noise. By tapping into the wealth of experience in the Fluid Dynamics and Acoustics Group on turbofan aircraft engines, it is hoped that a further understanding of the generation and transmission mechanisms of blade-pass noise can be achieved.
The long-term research into chain noise has continued with the ISVR chain rig very much at the centre of activities. The current focus is upon understanding the sensitivity of chain run length upon the chain sprocket phasing effect. A new eight-channel acquisition system has been commissioned to assist in these studies.
A number of silencer design projects have been carried out and in most cases the Apex/Apin software developed by Professor Peter Davies has been used to good effect. The projects have ranged from a miniature, reverse flow, model aircraft system to a large railway locomotive system.
Many of this year' s vehicle activities have been related to the development of various modelling techniques.
Attempts are being made to combine simple textbook relationships with generic vehicle characteristics to produce a simple model of mid- and high frequency vehicle noise. Although not intended to replace the well established Statistical Energy Analysis techniques, such simple hybrid approaches, which are specifically developed for a given size and class of vehicle, can produce adequate predictions with less data input effort.
Another modelling method still under development is a simple inverse approach for determining the noise contributions within the interior of a road vehicle. The method continues to show promise although significant variations in the character of low frequency tyre noise between different vehicles is proving difficult to accommodate in a generically based model.
An area of study new to the Unit is the refinement of seat adjusters. A comprehensive characterisation of a pneumatic lumbar support system led to its major redesign. Changes were made to the pump' s mechanical balance, casing structures were improved, and appropriate air silencers were developed. Significant reductions in noise were achieved through these actions, and the system became inaudible (to most subjects) under the quietest of vehicle conditions. The noise of a mechanical seat adjuster was also characterised, but similar improvement in its noise quality were impossible due to the impulsive nature of the excitation inherent with the design.
Marine activities within the Unit have increased significantly over the past year, helped considerably by the commencement of the EU 'Soundboat' project. This project will improve the methods for measuring the exterior noise from leisure boats. The existing draft measurement methods are very weather dependent, require specific test sites, and are expensive to undertake. The new methods being developed are loosely based upon the vehicle drive-by methodology developed over the last 10 years for the automotive industry, which combines models of the source strength and corresponding transfer functions for each significant source of noise. One of the greatest challenges so far has been the development of robust (and disposable) measuring equipment that can perform in the severe marine environment.
Pass-by noise testing of high-speed craft.
More traditional yacht design projects have also been carried out. These range from new-build recommendations for pilot boats through to understanding a major vibration problem with a luxury ex-steam yacht built nearly 100 years ago.
Demand continues for the three different calibrated sound sources developed by the Unit. A Mk II high frequency sound source is now being designed to accommodate a higher performing driver unit and discussions are being held with a third party to develop a software-driven option.
PC-based multichannel real time analyser has been developed for in-house use. Although it is capable of performing all of the expected functions of such an analyser, it has the added advantage that it may be customised for specific applications. The new analyser is the main stay of our current marine activities and forms the core of a recently delivered end-of-line noise monitoring system for a pump manufacturer. The analyser has been met with widespread interest and the possibility of marketing the system is being considered.
Typical operational display of the newly developed frequency analyser.
The Unit is becoming increasingly involved in supporting users of its software. In most cases the support involves modifications and improvements, often to satisfy a particular project. Although implementing the technical changes is usually relatively simple, accommodating customer politics and procedures is sometimes less straightforward. One of the main software activities during the year has been the continuing development of a vehicle interior noise contribution cascading tool. The existing system for objective values is now being paralleled with the development of a subjective tool, such that the effect of change may be listened to as well as viewed as a spectrum.
In a reverse of last year's trend, the Engine Noise and Vibration Control course was close to capacity, whilst the number of participants in the Vehicle Noise and Vibration course was down. This was attributable to late cancellations by three companies for financial reasons that reduced the numbers by 13. The one-week Exhaust and Intake Silencer Design short course was over subscribed and those who attended appeared to relish the highly practical content. All three courses run by the Unit will be taking place again this coming year.
Bearing in mind the difficult trading conditions, merging of the units, and refurbishment of the laboratory, the year has been largely successful. We have landed a number of large and interesting projects which have kept us busy through most of this year and will continue into the coming year. This bodes well for 2003/04.
*Bagshaw, M. and Lower, M.C. Hearing loss on the flight deck - origin and remedy. The Aeronautical Journal of the Royal Aeronautical Society, 106(1059), 2002, 277-89.
Smith, M.G. and *Chow, L.C. Validation of a prediction model for aerodynamic noise from aircraft landing gear. 8th AIAA/CEAS Aeroacoustics Conference, Breckenridge, CO, USA, 17-19 June 2002, AIAA 2002-2581, 2002, 8pp
* Not working in ISVR
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For further information contactStuart Dyne ISVR Consulting,
University of Southampton,
Telephone: 023 8059 2162 (+44 23 8059 2162 from outside
Copyright © 2003 ISVR Consulting, University of Southampton.
Last modified by Mike Lower, 20 December 2013. Disclaimer and copyright notice