Workplace Noise Assessment
Background
Employers have had legal obligations to prevent damage to the hearing of workers from excessive noise at work since 1975 under the Health and Safety at Work Act 1974. More recently hearing is specifically dealt with under the Noise at Work Regulations 1989.
Sound is essentially a fluctuation in air pressure usually created from a vibrating surface such as a loudspeaker or a panel on a machine. These fluctuations in air pressure create sound waves that can be readily detected by the ear. The ear is very sensitive to these fluctuations, very small disturbances can be detected. Other sources of noise can be attributed to physical disturbances in the air such as those created by a jet engine. The larger the pressure fluctuations, the greater the sound pressure and the louder the noise. For the purposes of the Noise at Work Regulations 1989 any audible sound is treated as noise 
Why be concerned about the noise levels in your workplace? Noise can be defined as 'unwanted sound'. Even low levels can cause irritation and distraction, while high levels can cause permanent hearing damage. Individual perceptionof noise differs from person to person.
The main physiological problems associated with noise exposure are:
» Stress and other physiological illnesses,» Noise-induced hearing loss.
Noise-induced hearing loss will depend on the amount of sound 'energy' that a person is exposed to. Sound energy is a function of both the sound level and the length of the exposure. The hearing loss can be either temporary or permanent. Temporary hearing loss occurs where exposure to high levels of noise results in a reduction in the sensitivity of hearing. With temporary hearing loss, if the period of recovery is long enough then hearing sensitivity will return to normal.
There are three action levels at which the employer has to take certain actions. The higher the action level, the more the employer has to do to control the noise.
First Action Level - A daily personal noise exposure (LEP, d) of 85 dB (A)
Second Action Level - A daily personal noise exposure (LEP, d) of 90 dB (A)
Third Action Level - A sound pressure level of 200 Pascal's [Peak level of approx. 140dB (A)]. The LEP, d is the total exposure to noise throughout the day, taking account of the average noise levels in working areas and the time spent in them, but taking no account of any ear protectors worn.
The peak action level will need to be taken into consideration particularly where workers are exposed to infrequent but loud impact or explosive noises for example from guns or cartridge operated tools.
The regulations states that "every employer shall, when any of his employees is likely to be exposed to the first action level or above or to the peak action level or above, ensure that a competent person makes a noise assessment."
The regulations go on to state that the assessment will need to be reviewed when "there is reason to suspect the assessment is no longer valid, or there has been significant in the work to which the assessment relates". For example; installation or removal of machinery, changes in workload, work pattern, or machine speeds, changes in building structure or machine layout, machine wear or deterioration. In any event the regulations recommend that the interval between checks should not be longer than about two years.
The Assessment
Healthy Buildings International (HBI) can offer a range of services to help you comply with the noise at work regulations and dispense your duty of care.
The first is a noise level screen to assess whether there any areas that exceed the first action level.
The second level of survey is to conduct detailed monitoring of the area/building with an integrated sound level meter which calculates the daily noise exposure each employee could be exposed to. This service also includes monitoring individual employees during their shift.
Monitoring can cover either personal exposure using personal dosemeters, or static area surveys of each particular machine and frequency levels when operational.
HBI also can provide a detailed assessment of the suitability of any hearing protection provided by the company, based on the results of the survey and give further recommendations. Demarcation plans of the area surveyed, may also be provided, if required, to show regions of mandatory or recommended hearing protection.
Recommendations for the actions required under the Noise at Work Regulations, to minimise employee's exposure, are detailed in a comprehensive report.
