H 20.002 Noise
Rev 03 [Jan 09]

Designing to make the management of noise in construction easier

Introduction

1. Designers can play a major part in making it easier to manage noise in construction.

2. Noise is a health hazard, which has a cumulative effect that could, eventually, lead to deafness. Unfortunately, in construction, high noise levels are encountered in many situations, exposing a large number of workers to a potential health hazard.

3. The most effective way of reducing exposure to noise is to design it out of any process.  However, it is recognised that with the current state-of-the-art plant and machines, this is not always possible. In these situations, designers should concentrate on not creating conditions in which the effects of noise are exacerbated.

4. This guidance note gives advice about how designers can limit the effects of noise.

Hazards associated with noise

5. Noise has a cumulative effect on a persons hearing.  Continuous exposure to noise above 80dBA, could lead to impaired hearing and, in the worst case, deafness. Employers are required to offer hearing protection when the average exposure is above this level. When average exposure is above 85dBA then hearing protection is mandatory. Speech is generally about 60dBA and it is certain that construction sites normally exceed the action levels. Designers will need to assume that noise is an issue that needs to be considered and take steps to reduce exposure to it.

What designers should do

6. Designers should give consideration to measures, which either remove the hazard of noise or lessen its cumulative effects.

7. Although exposure to noise in construction is inevitable with much of the state-of-the-art plant that is available, there are some construction processes, which are no longer necessary.  In these cases, designers should not specify work, which requires such processes to be carried out.  For example:

• a) Scabbling “green” concrete to achieve a bonding surface is not always necessary.  Instead, designers should specify:
  • i) retarding and washing off the joint interface;
  • ii) cast in proprietory joint formers;
• b) Saw-cutting joints in concrete should be avoided and cast in crack inducers specified instead;
• c) Chasing walls for services should not be necessary:
  • i) in new buildings, built-in ducting should be specified;
  • ii) in existing buildings, consider overcoating existing plaster if it is sound enough to do so and build ducts in;
• d) Build proprietory ties into masonry joints instead of specifying site shot-firing;
• e) Avoid site drilling wherever possible, eg: specify cast-in anchors instead of the drill-and-fix type;
• f) Site grinding, cutting, etc should be kept to a minimum.  For example by:
  • i) detailing mesh reinforcement to suit designed bay sizes rather than cut to suit on site;
  • ii) specifying non-standard concrete blocks as specials, to be cut off site under controlled conditions;
• g) Specify road and slab bases, which do not require the use of noisy rollers, eg, dry-lean concrete;
• h) Avoiding vibro-compaction of ground.

8. The health risks associated with exposure to noise can be lessened, by reducing a workers continuous exposure to noise.  Designers may be able to affect either the duration of exposure by specifying processes that are of short duration or the level of exposure by designing for and specifying quieter methods. Examples include:

a) Designing the position of construction joints, etc, to limit the size of concrete pours to what can be achieved in two hours;

b) Designing for and specifying the quieter methods of driving piles, which are available.

9. In addition, to lessen the risk of increasing the intensity, designers should, if it is possible to do so, limit the number of noisy operations that need to be carried out in enclosed spaces with hard surroundings.  Situations in which the intensity can be increased include:

• a) Inside of box-girders – grinding welds, using powertools;
• b) The inside of concrete structures – usually, but not exclusively, a problem associated with refurbishment work;
• c) In sewers, box-culverts and manholes;
• d) In cofferdams.

10. Some plant has been designed with noise reduction attachments. Designers should find out about these items and, where it is possible to do so, modify their designs to suit their use, if it is necessary to do so.

Noise – some background information

Noise levels

11. Noise is measured in decibels, dB(A).  Decibels are measured on a logarithmic scale.  So when the decibels go up by a small amount, the level of noise actually goes up a lot.  For example, 73 dB(A) is twice as loud as 70 dB(A), ie, 70 dB(A) + 70 dB(A) = 73 dB(A).

12. We talk at 60 dB(A). There is consensus that if you have to shout to talk to someone who is about 2m away, this is an indication that noise is approaching levels at which it becomes a hazard.

13. Noise dies off with distance from the source.  For example, noise at 3m from an item of plant is four times greater than the noise at 20m away.

Where noise is encountered

14. On construction sites, most of the machines used are noisy, above action levels. Some examples of noise levels are given, in Table 1 below.

15. This means that people working on construction sites, close to one of these operations, is inevitably going to be exposed to the debilitating effects of exposure to noise above action levels.

16. In addition, in certain conditions, when reverberation is possible, the intensity of noise can be increased. Such increases in intensity are normally encountered in environments that are enclosed by “hard” walls and roofs, off which reverberation is possible, eg: brick, concrete, steel.

17. High intensity noise, ie, noise above 100 dB(A) is very damaging, even in very short durations. Therefore, some construction processes, eg, shot-firing using cartridge guns, should be avoided at all costs, because the effects of noise are cumulative.

Table 1 Likely noise levels associated with construction plant and machines [para 14]

Notes  Source – Noise in Construction [HSE] & OSHA
*  Short, very loud [impact] noises do most harm.
** The second action level for noise is 85 dB(A) 

Useful references

INDG362(rev1) Noise at work: Guidance for employers on the Control of Noise at Work Regulations 2005 HSE