Why is Noise a Health & Safety issue ?
Does that mean if the SPL is more than 85 dB, everyone must have ear protectors?
What do you mean by “At Risk”?
What do you mean by “High Risk”?
What if there are short bursts of noise, say from a riveting machine or a gun at a firing range?
Are these requirements going to change?
How will I know if there is a risk of noise induced hearing damage in our workplace?
What do I need to measure SPL?
What do you mean by “calibrated”?
What do I have to do before taking measurements?
Is it easy to take SPL measurements?
I have taken a measurement. How do I interpret the result?
What advice can you give about hearing protectors?
Do I need to do anything more if there is a “High Risk”?
Why is Noise a Health & Safety issue ?
The ear is a marvellous piece of engineering by nature. It has a huge dynamic range (it can pick up the quietest of whispers as well as very loud noises). However, exposure to loud noises like drills or discos, can result in the temporary loss of the ability to hear quiet sounds. This is known as temporary threshold shift. This happens because the ear’s sensitivity decreases to compensate for the continous loud noise. The ear normally recovers it’s sensitivity a few hours after the noise has stopped. For example, people coming out of a music concert shout because their hearing is temporarily affected.
Persistent exposure to noisy machinery or loud music can result in a permanent threshold shift. This is known as noise-induced hearing loss. This occurs gradually and often goes unnoticed by the sufferer for a long time. However, this loss of hearing is permanent.
Some sounds are very dangerous and can cause instant and permanent hearing loss by causing damage to the ear. Because of this danger to staff and visitors, the measurement and control of noise is an important Health & Safety issue.
Before we answer this, one needs to look at how noise is measured. The unit of measurement used for noise is a decibel and is abbreviated to dB. The term “Sound Pressure Level” is used to refer to the level of noise that is produced by a source as shown below:
| Source | Sound Pressure Level (SPL) |
| Library | 30 to 40 dB |
| Conversation | 50 to 60 dB |
| Loud radio | 65 to 75 dB |
| Busy street | 75 to 80 dB |
| Heavy lorry @ 7 metres | 90 to 100 dB |
| Disco |
100 to 110 dB |
| Metal workshop |
110 to 120 dB |
| Jet aircraft @ 25 metres | more than 140 dB |
Most of the experts agree that anything over 85 dB is loud and anything over 90 dB is very loud. Any sound over 140 dB is classed as very dangerous and can cause instantaneous damage to hearing.
Does that mean if the SPL is more than 85 dB, everyone must have ear protectors?
Not necessarily. Hearing damage is dependent on the exposure time as well as the level of noise. The louder the noise, the shorter the time in which hearing damage can occur. On the right is a link to a useful chart.
Below are some examples.
| SPL | Max. daily exposure
(At Risk) |
Max. daily exposure
(High Risk) |
| Less than 85 dB | no limit | no limit |
| 90 dB | 2.5 Hours | no limit |
| 95 dB | 45 minutes | 2.5 hours |
| 100 dB | 15 minutes | 45 minutes |
| 110 dB | 1.5 minutes | 5 minutes |
So for example, a piece of machinery producing 90 dB SPL is only operational for 1 hour a day, it does not pose a risk to hearing.
What do you mean by “At Risk”?
If the “At Risk” exposure times are exceeded, then there is a possibility of hearing damage. The following actions need to be taken by the employer.
Measure noise levels at least every 2 years or when there is a significant change to noise levels or exposure times. Make sure the records of these are kept.
Advise the members of staff who are affected about the risks to their hearing and tell how to minimise this.
Make hearing protection available to those who ask for it. Show staff on how to use and maintain these properly.
If possible, use noise reduction equipment to reduce noise at source.
What do you mean by “High Risk”?
If the “High Risk” exposure times are exceeded, then there is a significant possibility of hearing damage. The following actions need to be taken by the employer.
Reduce exposure to noise by the use of sound insulation, or by other means.
Make sure that members of staff working in “High Risk” areas use hearing protection.
Mark areas where there is a “High Risk” with notices. This is usually known as a Hearing Protection Zone (HPZ).
Ensure that other staff or visitors entering a HPZ wear hearing protection.
What if there are short bursts of noise, say from a riveting machine or a gun at a firing range?
If these bursts of noise greater than 140 dB, then this is considered a “High Risk” situation.
Are these requirements going to change?
There are revisions to these regulations that are due to come into force by April 2006. In general they reduce the “At Risk” and the “High Risk” exposure levels. This may well affect some organisations that are currently in the “No Risk” category by making them “At Risk”. The link on the right takes you to the revised Noise exposure chart.
How will I know if there is a risk of noise induced hearing damage in our workplace?
If people have to shout or have difficulty being understood by someone about two metres away, then you might have a problem. If in doubt, take a measurement of SPL around your workplace.
What do I need to measure SPL?
A sound level meter is essential to carry this out. There are many different types available.
If you are in an organisation where you perceive the risk to be low, then a low cost meter to check the sound level is probably all you need. Offices, schools, hotels, warehouses are examples of these. Sound level meters to make this measurement are usually available for a cost of around £100. They may not be highly accurate, but are adequate to provide you with a way of measuring SPL.
However, if sound levels in an organisation are so high that people are in the “At Risk” or “High Risk” category, then a more accurate meter will be required. Factories, airports and construction sites are examples of these. These can vary in price from £400 to £1000. They are designed to international standards and if calibrated regularly, will give accurate, repeatable results.
What do you mean by “calibrated”?
All sound level meters use a microphone. The way these behave can vary with temperature, humidity etc. and also can change with time. It is important to make sure that it is checked frequently to ensure that it is measuring correctly. This is carried out by the use of a small device, which produces a sound at a known level. The calibrating unit usually costs about £200.
What do I have to do before taking measurements?
Try and establish where the sources of noise are by using your meter and get a feel for the SPL. Then assess how long the source is used during the day and which members of staff are close to it. Below are examples of what you may find.
Example 1: In a busy office, there is a small room where all the printing takes place on three different printers. There are also two paper shredders in there and a number of computers. Members of staff go in occasionally to retrieve prints etc. or shred documents. No one is in there for more than 5 minutes at a time. However, the office junior spends a total of 2 hours in there in an average day.
Example 2: In a warehouse, the Goods Inwards section opens out to a loading bay. Trucks back on to this all day long. Members of staff are always at hand to check and sign paperwork, and help unload the goods. The trucks have their engine on for a total of 3 hours a day, and all staff working in Goods Inwards are affected equally.
Example 3: In a metal workshop, various items of machinery are used throughout the day. All operators working here are exposed to the noise for a period of 7 hours.
Is it easy to take SPL measurements?
There are a few precautions to take. If these are borne in mind, then taking a SPL measurement is quite straightforward. The detail will vary from one meter to the next. With all the sound level meters supplied by First Stop Safety, there is a comprehensive guide to taking measurements. Also included is information on the interpretation of the measurements.
I have taken a measurement. How do I interpret the result?
This is best shown by looking at the examples above.
Example 1: The measured noise level in the print room, with all the printers and the shredder running was 93 dB. Round this off to the next highest figure, 95 to allow for measurement inaccuracy.
Use the Noise Exposure Chart provided to work out the risk level. This shows that anyone spending less than 45 minutes in here is not at risk. Anyone spending more than 45 minutes in here is “At Risk” and anyone spending more than 2.5 hours in here is at “High Risk”. The measurements indicate that the office junior is “At Risk”. Your duties are as follows.
* See if you can reduce the noise from some of the printers by enclosing them.
* Advise the office junior about the risk of damage to hearing and offer hearing protection.
* Show this member of staff how to wear the protection correctly and maintain them.
Example 2: The measured noise level, in the loading bay, with a truck reversing into it was 87 dB. Round this off to the next highest figure, 90 dB, to allow for measurement inaccuracy.
The Noise Exposure Chart shows that everyone working in Goods Inwards is “At Risk”. Your duties are as follows.
* See if you can reduce the noise from the trucks, say by requesting drivers to switch off engines.
* Advise all goods inwards staff about the risk of damage to hearing and offer hearing protection.
* Show all goods in staff how to wear the protection correctly and maintain them.
Example 3: The measured noise level in the workshop, with all the machines running was 97 dB. Round this off to the next highest figure, 100 dB, to allow for measurement inaccuracy.
The Noise Exposure Chart shows that everyone working in here is at “High Risk”. Your duties are as follows:
* Reduce exposure to noise by the using sound insulation around some of the machines.
* Make sure that everyone working in the workshop uses hearing protection.
* Put up signs to identify the workshop as a Hearing Protection Zone (HPZ).
* Ensure that other staff or visitors entering the workshop wear hearing protection.
What advice can you give about hearing protectors?
There are many types of hearing protectors available. Usually they are supplied with information on their effectiveness. Once you
have a SPL measurement and exposure times, the selection of the appropriate hearing protector will be straightforward. Information on this is included with the sound level meters supplied by First Stop Safety.
Do I need to do anything more if there is a “High Risk”?
A lot can be done in-house with a noise level meter and information on its use. However, if many members of staff are at “High Risk” it is advisable to use the services of a noise professional. They will be able to advise on different methods of insulation, as well as ways of monitoring the hearing of members of staff.
First Stop Safety supply noise measurement packages. These include a sound level meter, calibrator, hard carry case as well as advice on how to take measurements. Also included is information on interpreting these measurements, and selection and provision of hearing protectors
Details of these are available on our website www.firststopsafety.co.uk
