Reducing Noise from Forges and Foundries
The Handbook of the Black Country Forging and Foundry Project (Part 1)

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

1 Noise and Vibration - basic questions and answers

1.1 What is noise? How is it measured?

Noise is unwanted sound. Sound is a form of energy which is transmitted through the air and is detected by the ear as rapid changes in pressure. The air is set into motion by the source of the sound, which is most often a vibrating surface or a turbulent flow of air. The loudness and character of a steady sound are determined by its frequency (measured in Hertz or Hz) and its level (measured in decibels or dB). In this handbook, noise levels will be stated in dB(A) - this is the noise level measured by a meter which simulates the response of the human ear to sounds of different frequencies. Noise levels in dB(A) are almost universally used for the assessment of noise in the community and in the workplace.

1.2 How does noise affect people?

Depending on the level of noise and the duration of exposure, noise can cause varying degrees of annoyance or difficulties in communication. It can disturb relaxation or sleep, or can have adverse health effects including damage to the hearing. This handbook is about noise affecting people living near industry. In this situation, the noise levels experienced are such that the worst adverse effects of noise are annoyance and sleep disturbance. Some noise may cause only minor and temporary irritation, but in other cases noise can cause such a strong reaction that an individual's ability to relax or concentrate is severely affected.

Peoples' response to noise, particularly to noise from outside their own home, is highly variable. Some people are far more or less tolerant than others, for a variety of reasons, many of them psychological. There are obvious factors such as 'lifestyle' - a person who is at work during the day is obviously less likely to complain about daytime noise than is the shift-worker next door who has to sleep during the day. However, an important factor is the attitude of the individual towards the source of noise - people are far less tolerant of noise if they think that the noise-maker is inconsiderate or unreasonable.

1.3 What about vibration?

Noise and vibration are inseparable - noise is generated by a vibrating surface or body of air or gas. However, vibration itself is a potential cause of problems. Some heavy engineering processes, particularly the operation of forging hammers, can result in significant energy being transmitted to the ground through machine foundations. This can be transmitted to nearby houses and can sometimes be felt as actual motion, because the human body is a very sensitive vibration detector.

1.4 How does vibration affect people?

High levels of vibration can cause physical personal injury or damage to buildings. However, vibration from industry affecting nearby houses is never so intense that there is any conceivable risk of any health effects, and building damage from any source of ground-borne vibration is extremely rare. However, vibration can be annoying and disturbing.

Apart from causing detectable (although in fact very slight) motion in nearby houses, ground-borne vibration from industry can also cause noise problems in these houses. This is because the internal surfaces of houses (walls, floors and ceilings) can be caused to vibrate by vibrations transmitted from the ground through the foundations and building structure. These surfaces can then radiate low-frequency noise ('thumps' and 'rumbles') rather in the manner of large loudspeakers. People living near factories containing equipment such as forging hammers, large presses or guillotines can sometimes hear the resulting 'thumps' inside their houses, although the vibration itself - the actual motion of the structure- is too slight to be felt. Ground-borne vibration can also be detected in other ways - objects such as slightly loose central heating radiators, and glasses or china in light contact, may squeak or rattle.

Residents who can feel vibration, or hear the 'thumps' and 'rattles' it sometimes causes, are often more concerned about the possibility of damage to their houses (which is most unlikely to be caused) than they are annoyed by the actual disturbance to themselves.

Problems arising from ground-borne vibration are relatively rare, although drop-hammers can cause detectable ground vibration up to around 100 metres away, and sometimes at greater distances in some ground conditions. This handbook concentrates on the far more widespread situation where houses near forges and foundries are affected by airborne noise. However, the possibility of a 'noise' problem being a vibration' problem should be borne in mind - noises caused by ground-borne vibration must be distinguished from the effects of noise which is transmitted through the air (airborne noise) since different control methods are required and incorrect diagnosis can lead to costly wasted work. Further information about noise and vibration will be found in Annex 2.

1.5 How much noise is acceptable?

This section explains briefly the Standards and Regulations which apply to noise from industry in England. There may be minor differences and exceptions in Wales. Scotland and Northern Ireland. Different standards and Regulations will apply elsewhere.

From a new site or building...

Where planning consent is required for a new site, new buildings or a change of use, this consent often includes conditions to limit noise emission. These conditions might include restrictions on hours of use or methods of working, or they may specify maximum noise levels which are not to be exceeded at specified times of the day or night. These Conditions are enforced by the Local Authority. A breach of a planning condition can lead to an Enforcement Notice and prosecution. If noise affecting other premises amounts to a nuisance, a Local Authority can also use its powers under the Environmental Protection Act (the 'EPA' - see below) to abate the nuisance.

If there is an established use....

Many industrial sites do not have a formal planning consent, because a current use which has been carried on for more than ten years can be considered lawful. Many forges and foundries fall into this category. In these cases, if noise causes a nuisance to neighbours a Local Authority would use its powers under Section 80 of the EPA. If the Local Authority is satisfied that noise amounts to a nuisance, it has to serve an Abatement Notice. The company can appeal against a Notice within a specified period. Non-compliance with a Notice can lead to prosecution. If a company can show that it has applied the best practicable means of reducing noise (often termed 'Best Available Techniques' or 'BAT') this can provide a ground for an Appeal against the Notice or for defence against prosecution.

Where noise is causing a nuisance, private individuals can take action against an industrial site under Section 82 of the EPA, or under common law, even when the Local Authority choose not to do so. Such actions are rare, however.

Noise is a nuisance when it materially affects people's amenity. There are no fixed limits for industrial noise affecting houses - what is or is not considered acceptable or a nuisance depends on local circumstances. However, the following table illustrates the general range of unacceptable and acceptable noise levels from industry in a 'typical' built-up environment of mixed residential and industrial areas.

	Acceptable	Complaints expected	Unacceptable
Day (7 am - 7 pm)	50 - 55	55 - 60	60+
Evening (7 pm - 11 pm)	45 - 50	50 - 55	55+
Night (11 pm - 7 am)	40 - 45	45 - 50	50+

Table 1: Range of noise levels in dB(A) from industry - as measured outside nearby houses. Levels are average (L_eq) levels - see Annex 2.

These are 'broad brush' values and must not be taken as specific guidance for any particular site or situation. Higher noise levels might be acceptable in areas exposed to high levels of road traffic noise from trunk roads or motorways. Lower noise levels might be needed in quieter areas. An important factor is the character of the industrial noise. Noise which contains bangs and crashes is far more annoying and disturbing than steady noise of the same average level. The regular 'banging' caused by forging hammers is a particularly distinctive and potentially disturbing noise. For these types of noise, the noise levels in the Table should be reduced by at least 5 dB(A).

1.7 A widely used British Standard

There is a British Standard (BS 4142 - reference 1) which sets out a method of predicting whether noise from an industrial site is likely to provoke complaints. This standard is based on comparing the noise (measured or predicted) from the premises, as received at any house, with the background noise level at the same position when the industrial operation is stopped. The method includes a means of allowing for the 'character' of the noise, by penalising noise which contains bangs, crashes, whines or hums.

Evidence based on the use of BS 4142 is generally accepted in the Courts to demonstrate (or to dispute) the existence of a noise nuisance. Noise limits in Planning Conditions are usually based on consideration of BS 4142. The Standard is widely used (and often misused) and will inevitably be quoted whenever an industrial noise problem arises. However, proper application of the Standard requires expertise and judgement and a good understanding of its limitations.

1.8 Other Controls - Current and Future

Some companies operate voluntary environmental policies and procedures which include the assessment of noise emitted to their locality. These procedures might include, for example, regular noise monitoring at key locations and a method of assessing the extent of any change in noise emission likely to result from changes in plant or operating methods. Some companies formally accredit these policies under ISO 14001 (ref 2). In some sectors of industry, ISO 14001 accreditation is a customer requirement.

The introduction of Integrated Pollution Prevention and Control (IPPC) is likely to have a significant impact on the way noise from foundries and forges is controlled. IPPC will broaden the scope of existing pollution controls , which currently apply to certain industrial processes (including ferrous foundries and but excluding forges) to include noise and vibration. One objective of IPPC will be to encourage good practice (BAT).

1.9 Workplace noise

This handbook is not concerned directly with noise in the workplace, although reducing noise 'at source' by quietening a process or operation can often result in benefits both in the workplace and in the neighbouring area.

Noise levels in the workplace are covered in the UK by the Noise at Work Regulations 1989 (ref 3). An HSE document (ref.4) explains the Regulations and gives further guidance. New regulations on noise at work will appear in a revised EU Physical Agents Directive, currently being discussed. These changes will work through into UK regulations.

Summary - Standards and Regulations

Regulations and enforcement procedures relating to environmental matters. including management of noise, are constantly changing. As far as possible. keep up to date by extracting information from trade journals and government circulars Trade Associations are a major source of such information.

Reducing Noise from Forges and Foundries The Handbook of the Black Country Forging and Foundry Project (Part 1)