A noise survey involves taking noise measurements throughout an entire plant or a particular section to identify noisy areas. A survey is used to establish whether employees are being exposed to occupational noise levels exceeding the exposure limits set by the regulations (in the UK, the Control of Noise at Work Regulations 2005) or even the limits set by the company. It is worth noting that the UK is not alone in this and that numerous countries have developed workplace standards to ensure that the average level to which an employee is exposed during an 8 hour day does not exceed 85dB(A).
Why carry out a noise survey?
Noise surveys provide useful information which enables a safety professional to identify:
- Areas where employees are likely to be exposed to harmful levels of noise
- Machines and equipment which generate harmful levels of noise
- Operatives who might be exposed to unacceptable noise levels
The survey should be conducted in an environment where noise is likely to be harmful such as, for example, an assembly line or workshop. In most instances, the survey will involve measuring noise levels with a sound level meter. Noise level readings are taken at a suitable number of positions around the noisy area. A noise map can be produced by drawing lines on a sketch between points of equal sound level, these maps provide very useful data by clearly identifying zones where there are noise hazards. You can find out more about workplace noise surveys and noise action limits on our Solutions pages.
What’s involved in a noise survey?
Noise can be measured using a sound level meter which reads Sound Pressure Levels (SPLs) in dB(A) and the highest noise level reached, the peak sound pressure in Pascal (Pa).
There are two basic types of sound meter – integrated and direct reading meters. Meters which integrate the reading provide an average over a particular period of time, which is an essential technique where there are large variations in sound levels. This value is known as the continuous equivalent noise level or Leq which is normally measured or normalised over an 8 hour period.
The sound level meter, or indeed any noise measurement device, must be calibrated before and after each measurement session. To take measurements, the sound level meter is held at arm’s length at the ear height for those exposed to the noise. Remember to make a measurement at each ear!
When assessing the risk of loss of hearing, the microphone position should be as close as possible to the ear of the operative for whose benefit the noise exposure data is being taken. For a stationary worker, the microphone should be positioned above the shoulder or as near as possible. If the employee works in a standing position, the microphone should be positioned preferably 1.5 metres above the floor. Finally, if the employee works in a sitting position, the microphone should be positioned at 1 metre above the floor.
In working environments with impulse, intermittent or variable noise levels, (but also in cases where a worker’s movements cannot be followed or accompanied), the sound level meter is not designed to determine a person’s average exposure to noise over the entire or part of the shift. One solution is to use a noise dosemeter also known as a Personal Sound Exposure Meter (PSEM) which sits on the shoulder of the selected operator and records the noise exposure, then statistically determines noise over similar exposure groups. Noise dosemeters can be worn for a single day or over a few working days depending on the consistency of the tasks performed each day. In this case, there is no need for the person responsible for taking the noise measurements to be in attendance. The noise data will be collected and downloaded for analysis at the end of the measurement period.
If you already have your own noise measurement equipment, you will be familiar with the process. If you are in the early stages of implementation, you may want to research this further and attend a short course to refresh your knowledge or learn about the technique further. Why not join one of our noise at work awareness courses and learn from practising acousticians the basics of undertaking a noise survey before you conduct one in your own workplace?
Can’t wait? Call Pulsar Instruments now on 01723 518011 and we will be happy to answer your questions.
Related products of interests:
If you are not sure about the Law or noise limits that apply to your industry, please refer to our sound control advice blogs here or consult the advice on the HSE website.
Find out more about the Noise at Work Regulations.