Noise Measurement Uncovered

An eight-point guide to choosing the right noise-measuring equipment

According to HSE statistics, approximately 1.7 million workers are thought to be exposed to noise above levels considered safe, and it is estimated that around 21,000 individuals who worked in 2009/2010 suffered hearing problems as a result of their occupation.

In an attempt to reduce this level of hearing damage, noise legislation designed to protect hearing and prevent noise nuisance is becoming tougher and more widespread. As a result, the importance of noise control in the working environment is becoming an increasingly recognized and widely discussed issue, and employers are expected to measure the level of noise in the workplace so that appropriate preventative action or protective equipment can be introduced.

But noise-measurement equipment is needed to carry out this activity, and with so many choices of equipment available and with prices ranging from £20 to £5,000, deciding which one to buy can be very confusing – and expensive if the wrong choice is made. To simplify this process, Cirrus Research have produced an eight-point guide with advice on how to choose the best noise-measurement tools for a particular application, as well as an outline of some of the issues that need to be considered after the equipment has been purchased. The following comprises an abridged version of the full guide.  

1. Do the measurement functions comply with standards, regulations or guidelines?

The Control of Noise at Work Regulations 2005 requires the following measurements for compliance:

1. The equivalent continuous A-weighted sound pressure level (LAeq)
2. The maximum C-weighted peak sound pressure level (LCPeak)

It is important to have the right sound-measurement equipment for the right situation. There are many situations where using a hand-held sound level meter is not possible for both practical and safety reasons, such as employees with complex working patterns. This is where a noise dosemeter is the ideal measurement tool, because it can be worn for the whole working shift, continually measuring the noise levels with no further calculations required.

2. Does the equipment come with all of the accessories required?

It is always advisable to purchase a sound level meter or noise dosemeter as a complete kit and avoid combining units from different manufacturers. In general, the kit will contain the instrument, a suitable acoustic calibrator, a windshield and a protective carrying case. One of the most important accessories is an acoustic calibrator. All noise measurement standards state that an instrument must be calibrated before and after each use. Without an acoustic calibrator this cannot be done and, therefore, any measurements made could be inaccurate. The windshield will help protect the microphone from damage, even indoors.

3. The importance of recalibration and servicing

Noise measurement instruments are precision tools and the level of accuracy required from them is very high. Reputable manufacturers spend considerable time and effort to ensure their instruments meet these standards. It is important, therefore, to keep the equipment at the same level of accuracy as when it was purchased. An instrument from a trusted manufacturer and meeting the latest standards should come with a calibration certificate, and when recalibrated its performance should be checked against the original specifications and standards. To do this, an acoustic calibrator cannot provide enough information about the instrument’s performance, as the microphone capsule needs to be removed. With many low-cost instruments the microphone cannot be removed, therefore, the recalibration should be carried out by the original manufacturer or by a qualified calibration laboratory.

4. Does the equipment meet the specifications required?

The performance of sound level meters, noise dosemeters and acoustic calibrators is set out in national, European and international standards. The latest sound level meter standard gives two levels of accuracy – Class1 and Class2. The Control of Noise at Work Regulations 2005, which is in force in the UK, states that, with regard to sound level meters, ‘Your sound level meter should meet at least Class 2 of BS EN 61672 – 1:2003. Personal noise dosemeters have their own standard (BS EN 61252:1997) to which they must comply.

5. Make sure the equipment comes with clear instructions

The level of training and experience required to operate complex sound level meters can often get in the way of making good-quality noise measurements. However, a simple instrument that requires less training to operate might not give an accurate enough measurement. An expensive instrument may provide the data required, but the level of training needed could be expensive too. It is recommended, therefore, that users choose an instrument that meets their practical requirements while keeping the instrument as simple as possible and the cost realistic.

6. Make sure the equipment is simple to use, straight out of the box

Ensure that the chosen product is user-friendly. Ideally, the product should allow the user to see all relevant, important information in one place quickly, making it easier for him or her to report the measurements. At the very least, the ‘on’ and ‘off’ buttons should be obvious, but it is concerning to note that on some equipment, even these fundamentals are unclear.

7. Make sure the equipment is ‘futureproof’

When looking at different manufacturers’ products, questions should be asked to find out about how your investment will be supported. A reputable manufacturer should:

• regularly conduct research into noise-measurement regulations and requirements to ensure that they are constantly up to date with changing needs
• have an established research and development team that ensures their equipment contains the latest functionality to meet all user requirements
• offer free software updates so users can continue to reap the benefits of their equipment investment for years to come
• provide equipment upgrades so users can easily change the use of their equipment without having to invest in brand new hardware

8. Does the equipment come with all the software needed to get the best out of it?

Most noise-measurement equipment does not come with reporting software as standard. Users may only get the basic downloading software supplied with the instrument and, therefore, should check what is included. Putting together a report of findings can be time-consuming, so it is advisable to ensure that the equipment is supplied with full reporting software for free; many providers charge a license fee for this, which can prove very expensive.

For further information or to acquire the full version of the eight-point guide, call Cirrus Research on tel: (0845) 230 2434’ or visit: www.cirrusresearch.co.uk