Reducing Noise from Forges and Foundries
The Handbook of the Black Country Forging and Foundry Project (Annexes)

Written by Bob Davis
Original version © 2002, ISVR University of  Southampton.  All rights reserved.

Annex 1

The Black Country Forging and Foundry Project

The Background

This project was conceived in 1996 by forging and foundry industry groups, the Black Country local authorities (the Boroughs of Dudley, Sandwell, Walsall and Wolverhampton) and the GMB Union. It was perceived that companies in these industry sectors were experiencing a growing number of complaints from local residents concerning the environmental impact of their operations, from smoke, dust, fumes, odour, vibration and noise. These problems were to a large extent due to the location of the forges and foundries in the Black Country. These traditional industries are often based on sites which are within or close to residential areas.

There was a general concern that the profitability and even viability of some companies might be seriously compromised by adverse community reaction to their operations, with consequent effects on the local economy and on employment. The extent of the perceived problem was investigated by questionnaire, which was sent to approximately 170 forges and foundries during October and November 1996. The company list was compiled by the GMB Union from information provided by the Confederation of British Forgers (CBF), the British Foundry Association (BFA), local authorities and other sources. From this survey, it was concluded that a significant number of companies, accounting for perhaps 3000 jobs (out of a total of 10,000 in this industry sector in the Black Country) were receiving complaints about environmental problems which they thought might adversely affect their ability to maintain or expand their businesses.

Noise was clearly identified as the most widespread cause of unresolved problems.

As a result of this preliminary survey, a project proposal to investigate environmental noise and vibration in the forging and foundry industries was developed jointly by industry, local authorities (led by Dudley MBC) and the GMB Union. This proposal was submitted by Dudley MBC to the Government Office for the West Midlands, and was accepted for grant assistance under the Regional Development Fund in November 1997.

The Objectives

The overall objectives of the project were:


To make contact with (as far as possible) all forges and foundries in the Black Country area and to identify companies interested in participating in the project.

To collate the experience of these companies and to identify the principal causes of environmental noise and vibration problems in these industries.

To carry out a review of published research into noise and vibration in these and related industries.

To identify the techniques and solutions currently available to deal with the most widespread noise and vibration problems experienced by forges and foundries, and to identify where innovative solutions might be required.

To carry out, if appropriate, theoretical and experimental research into novel methods of noise and vibration control, suitable for the specific conditions in these industries.

Reports on the Research phase of the project can be seen on-line on the CMB website (see cover page for contact details)

Pilot Projects

To set up, within forges and foundries, pilot projects to demonstrate and further develop cost-effective and practicable methods of noise and vibration control. To implement the pilot projects.

Informing the Industries

To disseminate the project outcome throughout the industries through organised visits to completed pilot projects, journal articles, presentations and other media.


Project Organisation

The progress and direction of the work was supervised by a Steering Committee comprising:

N Powell    Dudley MBC
R Winzer    Dudley MBC
J Mundell    Woodcote Industries Limited (CBF)
J Wood    Caparo Engineering Limited (CBF/BFA)
J Young    Henley Foundries Limited (BFA)
B Johnson/C Humphries    GMB Union
B Parkin/G Field    CBM (Confederation of British Metalforming)
J Parker    CMF (Cast Metals Federation)

Some meetings were also attended by G Johnston (representing S Murphy MEP). Contracts for technical work were placed with the following consultants:

ISVR Consulting, University of Southampton
(Acoustics Consultants)

Paul Mantle Partnership, Halesowen
(Building Consultants and Quantity Surveyors)

Engineering Design Partnership, Alcester
(Building Services Consultants)

Structural Design Services Ltd., Stourbridge
(Consulting Civil & Structural Engineers)

Tunnicliffe Wall Associates, West Bromwich
(Building Services Consultants)

Contracts for video/CD production were placed with: 
LBV Television, Northorpe, Lincolnshire.


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Annex 2
Explanation of Various terms - Noise and Vibration

Frequency and Hertz

Frequency (or pitch) is measured in hertz (Hz) or cycles per second. The normal human ear can detect frequencies between about 20 Hz and 15,000 Hz, although it is most sensitive to sound in the range of frequencies between 500 Hz and 5,000 Hz.

Sound at a single frequency of (say) 100 Hz might be described as a low-pitched 'drone' or 'hum'. Sound at a frequency above 1,000 Hz might be described as a 'whine' or 'whistle;. Most industrial noise arises from a large number of machines and processes and contains a range of frequencies.

Noise level and decibels

The magnitude of the changes in air pressure are used to determine the sound (or noise) level. The human ear is very sensitive and can detect very small repeated changes in air pressure, as low as around 20 micropascals (20 μPa or 2 × 10-5 Pa). Repeated changes in pressure greater than about 200 pascals are perceived as painfully loud noise and can damage the hearing instantaneously. Even this is a very small change in pressure compared with the mean steady atmospheric pressure of 100,000 Pa (105 Pa). For a number of reasons which we do not need to explain here, noise levels (or sound pressure levels) are almost always measured in decibels (dB). In decibels, the range of sound pressures between 20 μPa and 200 Pa is represented by a scale from 0 dB to 140 dB. Most commonplace sounds have levels between about 20 and 100 dB. The decibel scale is logarithmic - each increase of 10 dB means that the sound energy has increased by 10 times, so that (for example) if a machine produces a noise level of 70 dB, ten machines of the same type would produce 80 dB and 100 machines would produce 90 dB. It follows that decibel levels cannot be added in the normal way - two machines each giving 70 dB would give 73 dB, not 70 + 70 = 140 dB (which would be the noise level produced by 10 million of these machines!)

Measuring noise level

Noise levels are most often measured using a sound level meter. This is a hand-held instrument using a microphone connected to an amplifier and signal processing circuitry to provide a direct indication, usually on a digital display, of the noise level in dB.

As pointed out above, the human ear is not equally sensitive to all frequencies of sound. This means that a simple statement of a noise level in decibels does not describe the apparent loudness of the noise. This has been overcome to some extent by the use of electronic filters or 'weighting' networks in sound level meters to simulate the frequency response of the ear. For most purposes, the weighting network called 'A' is used. Noise levels measured using a sound level meter using the 'A' weighting network are expressed in dB(A).

Many sound level meters, except the simplest, can also provide information about the frequency content of the measured noise as well as giving an overall dB(A) level. This extra information is often vital for identifying a particular source of noise or for devising methods of noise control. The most basic form of frequency analysis is so-called octave band analysis, where the noise can be 'split' by electronic filters into frequency bands which are identified by their centre frequency. The standard octave band centre frequencies are 63, 125, 250, 500, 1000, 2000, 4000 and 8000 Hz. More sophisticated meters and specialist frequency analysers can analyse noise in more detail using filters of narrower bandwidth.

What if the noise is not steady?

The level of a steady noise can be described by a single measurement in dB(A). However, noise levels are rarely steady. Noise may fluctuate slowly, or may change rapidly from second to second. Noise caused by impacts, such as the operation of a forging hammer or castings being dropped into a steel bin, or by explosions such as gunshots, is termed 'impulsive'. Additional units of measurements are needed to describe non-steady and impulsive noises. Three commonly-used measurement units (there are many others) are:

The equivalent continuous level or Leq,T This is a time-average level over time T. For example, if a noise level is stated as being 60 dB(A) Leq,5min this means that the time average level over a period of 5 minutes was 60 dB(A).  The time average level gives no information about the range of noise levels actually occurring during the measurement period.

The maximum noise level Lmax. Lmax is the highest noise level during the measurement period. For impulsive noises, the value of Lmax depends on the response time of the sound level meter. Most meters have two response time settings termed 'fast' or 'F' and 'slow' (S), which are defined by international standards. A measurement of Lmax using the 'fast' setting would be expressed as (for example) 70 dB(A) Lmax(F).

The noise level exceeded for a given percentage of the time, LN. The L90 noise level is often used to describe the noise level during the quietest periods of a measurement. L90 is the noise level exceeded for 90% of the time - for example, 45 dB(A) L90.

The meaning of these noise measurement units is further illustrated on the figure below, which shows the values of Leq, L90 and Lmax for a measurement period during which the noise varies in level with time and includes some impulsive sounds (the sharp 'peaks' on the graph).

Fig 5: Different noise measurement

Fig 5: Different noise measurement units



Measurement and assessment of vibration is outside the scope of this handbook, and it is likely to be beyond the scope of most manufacturing companies. Measurements generally involve the use of transducers called accelerometers, which are fixed to the surface (the ground or part of a building) to be measured. Vibration intensity or level is commonly expressed in terms of the peak particle velocity (p.p.v.) in millimetres per second (mm/s), although other units are widely used.

Standards for assessing the response of people and structures to vibration are given in refs 5 and 6.


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Annex 3
Sources of Information

References in the text

  1. British Standard 4142:1997. Method for Rating Industrial noise affecting mixed residential and industrial residential areas.
  2. ISO 14001:1996. Environmental management systems - Specification with guidance for use.  Update: A later version of ISO 14001 was published in 2004
  3. The Noise at Work Regulations 1989. (Statutory Instrument SI 1989/1 790, as amended by SI 1992/2966 and SI 1996/341)  Update:  The Noise at Work Regulations 1989 have been superseded by the Control of Noise at Work Regulations 2005
  4. *Reducing Noise at Work. Guidance on the Noise at Work Regulations 1989. HSE Books No. L108. Health and Safety Executive 1998.  Update: This publication has been superseded by "Controlling Noise at Work. Guidance on the Control of Noise at Work Regulations 2005." The publication no is still L108.
  5. British Standard 6472:1992. Guide to evaluation of human exposure to vibration in buildings.
  6. British Standard 7385: 1993. Evaluation and measurement for vibration in buildings. Part 2: Guide to damage levels from groundborne vibration.


Other suggested reading

The following provide a useful introduction to the principles and practice of noise control.

(i) Noise Control in Industry. Sound Research Laboratories Limited. Pub. E & F N Spon.

(ii) Woods Practical Guide to Noise Control. Pub. Woods of Colchester Limited.

(iii) *Sound Solutions. Techniques to reduce noise at work. HSE Books. HMSO (1995).Update: This document is out of print but the HSE have placed the case studies on their web site.

*Note: HSE Publications on noise are directed primarily towards reducing noise in the workplace. However, many of the principles are equally applicable to the reduction of neighbourhood noise. Some HSE reports and notes are specifically about reducing noise in forges and foundries.



The following organisations can provide general information on how to approach noise problems, and can give assistance in locating specialist advice:

Confederation of British Metalforming
Cast Metals Federation

Both at:

National Metalforming Centre
47 Birmingham Road
West Bromwich
B70 6PY
Tel: 0121 601 6350/6390


Association of Noise Consultants

6 Trap Road
Guilden Morden
Nr. Royston

 Update: The Association of Noise Consultants has moved to:
 105 St Peter's Street
 St Albans
 AL1 3EJ
 Tel: 01727 896092 Fax: 01727 896026




Copies of a video/CD together with the printed version of this booklet on noise reduction methods in these industries can be obtained from;

Environmental Services
Dudley Metropolitan Borough Council
Mary Stevens Park

Tel: (01384) 814633  


Cast Metals Federation 
Tel: (0121) 601 6390  
Confederation of British Metalforming  
Tel: (0121) 601 6350  

Both at:

National Metalforming Centre
47 Birmingham Road
West Bromwich
B70 6PY

Contents  |  Part 1  |  Part 2  |  Part 3  |  Part 4  |  Part 5  |  Annexes 
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Original version © 2002, ISVR University of  Southampton.  All rights reserved.