Annual report 2003-2004
Every year from 1963 to 2010, the Institute of Sound and Vibration Research published its Annual Report. This is the chapter on ISVR Consulting for the year May 2003 - April 2004.
ISVR Consultancy Services
Manager Mr S J C Dyne
ISVR Consulting was formed on 1 January 2003 by the union of ISVR Consultancy Services with the Automotive Design Advisory Unit. Although the two separate units had been providing consultancy services for over thirty years, an increasing similarity in activities was a catalyst for the merger; the combined unit now acts as a comprehensive acoustics and vibration consultancy performing applied research projects, serving a wide range of clients in the public and private sectors. Unit activities form a significant component of the ISVR enterprise strategy but unit staff also make a small contribution to teaching on undergraduate, post-graduate and short course programmes in addition to publishing research output in conferences and journals.
ISVR Consulting operates on a commercial basis, with twenty full-time engineering and support staff, and is a founder member of the Association of Noise Consultants. The unit maintains close links with the ISVR research groups with a number of projects being carried out in collaboration with academic and research staff. The unit website www.isvr.co.uk includes full details of the range of services and facilities available.
Summary of activities
Consultancy projects are client-confidential. However, the following description of projects in progress during the reporting year illustrates the range of work undertaken and the general direction of consultancy activities. During the period nearly 400 enquiries were logged, with 129 becoming actual projects.
Several environmental noise issues have been studied. A coastal district council has engaged the unit to advise on the potential impact of the proposed reconfiguration of part of the docks within their region. Several projects have been carried out on gas turbine installations in the UK. Other environmental projects have concerned railway operations, motor racing, mineral extraction, waste collection and recycling centres.
The sustained demand for new homes has continued to provide a steady stream of projects for environmental assessments, according to the 'Planning and Noise Guidance Document PPG 24', and for the testing of the finished buildings, according to 'Building Regulations Schedule E'. During the year the unit became approved for this type of testing under the new scheme administered by the Association of Noise Consultants and a steady stream of compliance tests on local construction sites have been carried out. Guidance on improving the sound insulation in an identification suite has been provided to a police force.
A large environmental/industrial noise control study was carried out for a major oil company that has had a serious environmental noise problem for some time. The unit carried out an extensive investigation, involving field surveys, theoretical studies and scale modelling in the laboratory, to understand the nature of the problem and advice on remedial action. This demanding project involved academic staff working in collaboration with unit and oil company engineers. The remedial measures are in the process of being introduced in the plant with early indications of a successful outcome.
Test and experimental work
ISVR Consulting operates and manages the ISVR acoustic chambers, including the large anechoic chamber and reverberation rooms. There is continual demand from industry for product testing including sound power measurement and high intensity noise testing. A major aerospace project has involved extensive high intensity testing of electronic boxes supporting design review studies that have been undertaken to assess equipment response to high noise levels. The facility had to be enhanced to meet higher noise levels than had been required previously and is now capable of generating overall levels up to 168 dB including very high levels of low-frequency noise such as the demanding specification of 150 dB in the 10 Hz one-third octave band.
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 (HATS), and hearing aid testing. The main aims of the project are to compare the various national and international standards that are relevant to ear simulators and HATS, to examine how the standards relate to each other, and how the HATS from various manufacturers conform to the standards.
Trials work has continued at several ranges in the UK involving the measurement of the response of structures to air-blast and impact loading. This work has been complemented by the refurbishment of the departmental blast wave generator, which can produce a Friedlander form shock pulses with high overpressures in the tube with a working section diameter of 0.8m.
Vibroacoustics, modelling, aerospace and industry
The steady flow of research work from the commercial jet aircraft industry has continued unabated, with further work on the modelling of aircraft landing gear noise under the EU SilenceR project and the development of a hybrid ray/mode duct prediction method for Rolls Royce as part of the University Technology Centre (UTC). The airframe noise work has also benefited from a significant consultancy project on the control of noise from high lift devices on wings: the success of this project opens the way in the future to EU research contracts on the same topic.
During the reporting year the in-house finite element (FE) package expired and was replaced with commercial ANSYS code. This has greatly enhanced the FE modelling capability of the unit. There is a significantly improved interface with client's CAD data and we are now able to interface with the SYSNOISE boundary element code. These developments bode well for the future of numerical modelling in the group.
Light aircraft studies have included the diagnosis of vibration-induced power unit durability as well as new concept development. A small, low noise, power unit has been developed and statically demonstrated, with effort focusing upon base engine selection, gearbox design, propeller selection and exhaust silencing.
Projects for energy industries include the development of a computer program for estimating the vibrational response of gas pipelines to noise generated by valves and an investigation into the causes of excessive vibration and fatigue in gas processing plant, together with proposals for a solution.
Noise at work, subjective acoustics and communications
The Control of Noise at Work Regulations 2005, based on the EU Physical Agents (Noise) Directive, are due to replace the Noise at Work Regulations 1989 in February 2006. The new regulations will place some new obligations on employers and generally reduce the noise exposures or sound levels at which actions must be taken. Over the last year we have been assessing noise exposures for compliance with both the current regulations and the Physical Agents (Noise) Directive so that our clients are well prepared for the change.
Noise at work assessments have been carried out for: a Premiership football club where ground staff make heavy use of tractors, mowers, strimmers and other equipment to maintain the stadium pitch and the training ground; a drinks distribution warehouse where loads are made up for delivery to pubs and clubs and then loaded onto 'dreys'; police firearms instructors and trainees at a 50 metre indoor range (where advice was also given on acoustic treatment to the range as well as on use of hearing protection); crew wearing flying helmets with active noise reduction in a police air support unit aircraft; general woodworking and, specifically, woodworking for yacht restoration; loading of vehicles and heavy machinery onto ocean-going ferries; operating coin-sorting appliance; the manufacture of computer storage disks and metalwork instruction in the prison service. Although our work in call centres has reduced, we are still getting many enquires concerning noise exposures from headsets in control rooms. This year we have assessed noise exposures in a police control room, bringing our total up to 11, and in an electricity distribution network control room.
The introduction of the new Airwave or TETRA system for the emergency services has led to measurements of sound levels from earpieces used with the new TETRA terminals that replace police personal radios. We have also assessed the total noise levels experienced by police motorcyclists (on both marked and covert motorcycles) wearing new insert radio earpieces under the helmet.
We are carrying out a project with Cranfield University on behalf of Transport Canada into the use of sound to guide passengers to aircraft exits when visibility is poor. We have designed highly distinctive complex-tone sounds optimised for localisation. These sounds have been tested at ISVR and Cranfield and are as effective as broadband noise for localisation. Further trials are to be carried out in the aircraft cabin simulators at Cranfield.
Personal injury and other litigation work
ISVR Consulting has continued to offer expert evidence to support claimants and defendants in personal injury claims. The unit increasingly receives joint instructions advising the courts on technical matters on behalf of both sides in civil litigation. We have prepared reports for personal injury on: a person alleging damage from headsets in a control room; a person alleging exposure to high levels of ultrasound; a tugboat crew; a print worker; a road traffic accident victim; a military bandsman; a vehicle bodywork finisher and a bus driver.
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. One example is the extraction of faint speech from a recording of an employment grievance hearing while several speakers are simultaneously talking. In another case, a police force sought an opinion on whether noise from an in-car entertainment system might have contributed to a fatal road traffic accident. Critical listening to an audio recording was necessary to determine the frequency of use of a foetal heart monitor in a medical case. Slightly more unusual cases during the reporting year were a consideration of the vibration injury and hearing damage potential of bone-vibration transducers as used in military headsets and the potential for hearing loss caused by inhalation of volatile organic chemicals.
Besides the more traditional running engine test bed studies, this year saw a major re-visit to engine encapsulation. Significant reductions have been achieved in recent times in both base engine noise and the corresponding vehicle acoustic transmission; however, there is a suggestion that well designed enclosures or partial enclosures may be a viable alternative for reducing vehicle interior noise. By adopting appropriately designed enclosures, the engine's multi sources may be better matched with their respective vehicle transfer functions resulting in a potentially more cost efficient means of noise control.
A number of banger-rig-based engine-structure attenuation studies have been carried out with considerable interest being shown in aspects of both airborne and structure-borne sound quality. A study of the large ISVR structural attenuation database suggests that production engine structures, with few exceptions, are getting within a few decibels of optimal values (with respect to attenuation per unit weight). It is comforting to note that this achievement is in no small part due to the innovative ideas spawned by ISVR over the past 35 years.
The on-going chain-noise studies have in recent months produced some very useful information and the long-term goal of producing robust guidelines for the design of low-noise front-end chain systems is looking achievable.
With the ever-present requirements to reduce the size and cost of exhaust silencers, the Apex predictive software has been put to good use for studying concepts as well as assisting in the detailing of designs. With innovative layouts continually being considered the need is always present for the development of additional elements for Professor Peter Davies's software.
Vehicle activities this year have concerned a mixture of old and new issues. Interior low frequency 'boom' was first studied over 40 years ago, and although most modern vehicles have this inherent problem under control, it occasionally reappears with vengeance. A major characterisation and route tracking exercise recently completed on a production vehicle showed that the root cause of the boom was an unfortunate matching of structural responses. The exercise clearly demonstrated that although there are numerous mature boom solutions available, the continual drive towards higher torque diesel power units, softer component suspension and lighter body structures, means that the problem is far from being a thing of the past.
New vehicle issue are predominantly those of sound quality. Studies into making pneumatic seat adjusters inaudible continue, with the challenge becoming more demanding by the ever-tightening cost and weight constraints. A major multi-aspect sound quality clinic was run at a customer's conference centre. For one of the experiments, the ISVR Engine Noise Simulator was used to produce different engine sounds in a vehicle, and as ever, the spatial realism of the simulation was continually commented upon.
A number of noise reduction exercises have been carried out on vessels ranging from a large ocean going tug to a small sea life research vessel. Unlike the automotive industry, substantial reductions in noise and vibration are regularly achieved with relatively little effort, suggesting that the marine industry could well benefit from more comprehensive new build guidelines for ensuring good refinement.
The SoundBoat project continues to generate much useful data and recent attempts to model the pass-by noise of high speed planing vessels are beginning to look promising. The project has raised much interest in the industry and invited presentations to the Institute of Marine Engineering Science and Technology (IMarEST)and the Excel International Boat show have both been well received.
A Mark II version of the highly successful ISVR high-frequency sound source has now been launched. The major change has been the adoption of a cube-shaped case for the driver unit replacing the original cylindrical case. This modification was made in response to a number of customers commenting that when laid on its side, the source could roll around the laboratory floor.
One very challenging piece of instrumentation developed during the year has been an in-vehicle turbocharger noise gauge. An irregularly spaced four-microphone array has been developed to faithfully capture the (low level) tonal noise of interest, whilst the downstream analysis of the signals is carried out by a four-channel customised version of the ISVR EngWaves PC analyser. The device is currently undergoing infield calibration and evaluation by the customer and is expected to enter service in the near future
The EngWaves software signal analyser is continually being developed to satisfy individual engineer and customer needs. It has now become the most used analysis system for the Vehicle and Dynamics Group’s activities. The Automotive industry also believes it has much potential and although not yet fully developed, prototype EngWaves is now being adopted by an increasing number of customers.
A major software task has been carried out over the past year, in which a noise contribution analysis package previously developed by ISVR has been combined with some customer-developed and ISVR sound simulation algorithms to produce a practical tool for listening to all the contributing noise sources within a road vehicle. Although not yet fully completed, it has already had exposure and favourable comments from both Europe and North America.
The three short automotive courses were again successfully run. Both the Engine and Vehicle courses attracted a healthy 54% of delegates from overseas, and the Exhaust and Intake noise course was again at full capacity. The attendees appear to appreciate the informal and practical approach adopted by these courses. A large number of delegates attended the course on the recommendation of previous attendees, suggesting a high degree of satisfaction.
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