Industrial Noise / Noise at Work
This is an interesting subject that can appear complex, but it is always worth remembering what you are trying to achieve. This can be summarised as:
“Minimising or avoiding the risk of noise induced hearing loss in the workplace to comply with local, noise based, legislation”
Such legislation is usually based on a European Directive that is then modified to suit the needs of each particular country. For example, in the United Kingdom, the ‘The Control of Noise at Work Regulations 2005’ are based on the European Union Directive 2003/10/EC; usually called “The physical agents (noise)” directive and expanded upon by the Health & Safety Executive.
In the UK, research estimates that over 2 million people are exposed to noise levels at work that may be harmful.
How to protect the workers and meet the regulations?
The first action should be to obtain and read your national regulations and any advice leaflet. In the UK both can be found in the HSE (Health and Safety Executive) booklet L108 ‘Controlling noise at work’. This gives excellent and accurate advice in clearly marked sections. The data in the HSE booklet applies all over the European Union and is one of the best guides available in the English language.
Firstly you need to establish if you do, or do not, have a noise problem in each of your main areas or work zones. There are a number of simple rules to determine this (see below). However, to be absolutely safe, even if you are sure you do not have a noise problem, you would be advised to perform and document some simple noise measurements to provide long term evidence of your basic assessment. A calibrated, easy to operate, sound level meter such as the Model 14 or Model 82A Assessor would be an ideal choice to simplify this task.
As a crude guide, if you are in an area where the noise is intrusive but normal conversation is possible this would have a probable noise level of around 80dB(A). If people are working in this environment for 6 hours or more you would need to carry out a formal risk assessment.
If you need to shout at someone who is about 2 m away and this noise level occurs for 2 or more hours per day you need to carry out a formal risk assessment.
| Level in decibels ‘A’frequency weighted | Actions required to meet the regulations |
|---|---|
| Areas always < 75dB | Brief risk assessment only – no other action |
| Areas between 75 & 85 dB for a proportion of the time | Initial survey using an Leq meter or dosemeter |
| Areas where levels are likely to give an 8 hour exposure of 80dB(A) or more. | A full survey with clear identification of levels & corresponding actions; ideally with noise sources listed and personal exposure estimates for all workers likely to be at risk from noise induced hearing loss. |
Noise Risk Assessment survey – the basics
In Europe, once you have established that you have employees that are likely to receive an exposure of 80dB(A) or above you need to carry out a formal noise risk assessment survey.
To start you need to measure the noise levels and for this there are two equally acceptable methods. The first is by measuring noise levels using an integrating sound level meter and subsequently calculating exposure levels based on the duration of exposure to each noise source. The second uses a dosemeter, now formally called a Personal Sound Exposure Meter or PSEM to measure the exposure of each individual.
Pulsar Instruments Plc makes both types of instrumentation and leaves the decision to the user. Each method has its advantages but you need to decide which method is best suited to your specific task. If you need any help, please contact one of our technical team who will be pleased to offer you advice and guidance. Often a combination of approaches gives the best results and for this reason Pulsar has introduced its bespoke “Safety Professionals system”.
Sound Level Meter method
The guide requires an instrument that has the following minimum characteristics:
- *‘A’ frequency weighted Leq (time-average noise level)
- *‘C’ frequency weighted Peak around 140dB (LCpk)
- *At least IEC 61672 Class 2 accuracy
Each instrument within our Assessor range has a special ‘ready reckoner exposure table’ which is displayed after each measurement to help you. It also provides a ‘settled’ indicator to help you decide when the average noise level has stabilised. Note:- The formal symbol for A-frequency-weighted Leq as defined in IEC 61672 is LAT , but the use of Leq has become accepted.
Dosemeter or PSEM Method
To use a PSEM or dosemeter, the setting-up is similar to that of a sound level meter. The batteries must be charged and the unit must be calibrated before the measurement. The PSEM is then fixed to the worker as near to the ear as convenient and set running. In the case of the doseBadge, simply point the READER unit, with its infra-red communication, at the badge and press the ‘start’ button.
At the end of the working shift, the badge is stopped by pressing the ‘stop’ button on the Reader unit. The doseBadge is then removed from the worker and the data in each badge is downloaded to the Reader, where it is now available to inspect. The data can also be transferred to to a PC, using the Pulsar software provided, allowing you to efficiently analyse and report on the measurement.
A key benefit of the doseBadge system is that it gives the full time history of both ‘A’ weighted Leq and ‘C’ weighted Peak. This allows you to get a much clearer picture about real work patterns, rather than each worker’s subjective “opinion” as to the levels.
Time history of a full working day using the Model 22 doseBadge and dBlink software
What do we need to measure?
In industry two different noise metrics are used to determine the risk from noise. The main one effectively represents the overall energy or the “amount” of the noise and is described by LAeq and expressed as the continuous equivalent level (the average noise level), while the other represents the absolute highest pressure occurring, called the PEAK value, described by LCpk or LZpk.
Both the average value and the peak level are needed as while most hearing damage occurs as a result of noise exposure over a long period, a single very high value impulse can also cause damage.
The ‘energy’ metric in Europe, is legally defined in terms of LEX,8h, the average level over an 8-hour daily period. In the UK this is still called the LEP,d (daily exposure level) but both are essentially the same thing. Officially LEX,8h or LEP,d is the Leq (or average level) normalised to an 8 hour working day. Different actions need to be taken at different levels, but from 2006, there has also been the introduction of the new 87dB(A) legal limit which was a major shift in policy.
Measures to be taken when the Exposure Value is 80dB(A) or above
- Identify all the employees affected.
- Inform all employees of the potential risk to hearing
- Publish results
- Fit signs recommending the use of Hearing Protection
- Provide a choice of appropriate hearing protectors on request
- Provide adequate education / training to meet these requirements.
Measures to be taken when the Exposure Level is 85 dB(A) or above
- Areas concerned must be marked out and appropriate warning signs displayed.
- Personal Hearing protectors must be worn in these zones.
- An Audiometric Health Surveillance Program must be established.
- The exposure of employees must be reduced as far as reasonably practicable.
- Noise should be controlled at source (Engineering solutions, Insulation, Absorbent Lining, Enclosures etc)
‘Exposure Limit Value’Legal limit of 87dB(A) over 8 hours.
87dB(A) is the maximum permissible noise level exposure to actually impinge on the exposed person’s ear (including the use of hearing protection).
Do I need to make any additional measurements?
Once you have determined that noisy areas are generating dangerous exposure levels to workers you need to initially prescribe hearing protection. You then need to carry out a measurement of ‘C’ weighted Leq and / or a 1:1 Octave Band Analysis.
| ‘C’ weighted Leq | SNR method |
| ‘C’ minus ‘A’ weighted Leq | HML method |
| 1:1 Octave Band Analysis | Octave Band method |
Most hearing protection packages contain data for SNR, HML and Octave Band values. These can be used in conjunction with your measurements to prescribe suitable personal protection equipment (PPE) matched to your actual noise.
A Simple to use HSE Spreadsheet Style Calculator
A sound level meter which measures octaves exists in two forms, a REAL TIME ANALYSER or RTA, such as the Model 30 where each octave is measured simultaneously, or the serial method where each octave is measured one at a time, Assessor Model 84 is an example. From the 1:1 Octave Band data it is possible to calculate results manually or it can be done automatically by using the excellent Pulsar Analyser software. The software contains a database of hearing protection, so that the level at the ear is automatically calculated by the software.
Model 30 ~ PPE Instrument Color Coded
Field Calibration
Most legislation requires you to ‘field calibrate’ your sound level meter or PSEM before and after each measurement session.
If it is correct both before and after the readings, you have an excellent chance it was correct during them and the instrument, or more especially the microphone, has not been accidentally damaged. Pulsar Acoustic Calibrator Models 105 and 106 are the correct units for all these sound level meters and they have formal, legal, European Pattern Approval. Many users are careless about such routine calibration, but it is essential for compliance with the legislation, so always note that you have done this field calibration, in the report.
The Model 22 doseBadge system has an integral calibrator in the Reader unit, making calibration a straightforward task.
Note: In the older standards such as IEC 60651 and 60804, meters were classified as ‘Type 1’ and ‘Type 2’, but in the new standard IEC 61672, they are defined as Class 1 and Class 2.
Further Action
Clearly, the best thing to do is to reduce the noise AT SOURCE, by screening machines, slowing them down, changing technology or any of the many ways available. In many situations, this ideal is not possible to achieve and the reality is that hearing protection will have to be employed.
A Full Survey will include full details of all the noisy processes, in other words, mapping the various noise sources, determining the people exposed and the various levels; all obvious matters. The subsequent report should include immediate actions needed – such as ear defenders - as well as longer term noise reduction strategies. It is clear that in any noisy space, the loudest noise measured must be used for everyone in the vicinity, unless a separate measurement is taken at each worker’s location. Such a separate measurement is easily done with a PSEM.
Who should measure?
In the UK, a ‘competent person’ should do it. One way to become a ‘competent person’ is to attend a short course, typically four days in length, under the auspices of the Institue of Acoustics. These are excellent and after a short examination, they offer formal certification.
Pulsar Instruments Plc offers a “One Day” noise course, written and presented by members of the Institute of Acoustics that focuses on the basics of noise, current regulations, basic survey advice, noise control and the correct use of noise measurement equipment. In motoring terms, it is a course for drivers, not mechanics.