Integrating-averaging sound level meters and Leq explained
What is Leq?
If noise levels are rapidly changing over time then the 'average level' becomes an important tool in any noise assessment, this average is called the “Equivalent Continuous Sound Level“ and is abbreviated to Leq.
Knowing the Leq is vital if you are conducting noise measurements under the Noise at Work Regulations (2005); as stated above, it is the most commonly used value to describe sound levels that vary over time. More properly when we are talking about noise at work people refer to an A-weighted Leq or LAeq. Another slightly more complicated definition for Leq that is sometimes given is that a Leq is the sound level that would produce that same sound energy over a stated period of time when using a 3dB exchange rate.
Being an average level, Leq can go up and down but the longer it is measured for (time), the more stable the average gets, as it measures all the noise from the beginning of the measurement. If we were to get to this 'stable' value manually it would require multiple steps and many calculations to divide the sound exposure by the time over which the measurements were taken, however since the invention of more sophisticated integrating-averaging sound level meters we have these instruments to do all the hard work for us.
What to look for when choosing an Integrating Sound Level Meter
Regulation 5 of the Control of Noise at Work Regulations 2005 states that an employer should carry out a risk assessment and that the assessment shall include consideration of the level, type and duration of exposure, including any exposure to peak sound pressure'. Appendix 1 of the Regulations further define what should be measured :
'When making measurements to estimate the noise exposure of a person at work, you need to ascertain the equivalent continuous A-weighted sound pressure level (LAeq) that represents the noise the person is exposed to during the working day. You also need to ascertain the maximum C-weighted peak sound pressure level or levels the person is exposed to.'
So at a minimum, a sound level meter used for noise at work assessments must be capable of measuring the:
- Equivalent Continuous Sound Pressure Level (LAeq)
- C-Weighted Peak Sound Pressure (LCPeak)
As the instrument needs to measure, at a minimum, LAeq, it must, therefore, be an integrating-averaging sound level meter. It should also meet the requirements of Class 2 of BS EN 61672-1:2003 (the current standard for sound level meters) or Type 2 of BS EN 60804:2001 (the former standard). Optionally you might elect to use an integrating sound level meter that is also capable of measuring either or both:
- C-Weighted Leq (LCeq) for selection of hearing PPE using the HML method.
- Octave band frequencies for more accurate selection of hearing PPE and identification of noise sources.
Pulsar Instruments offers a range of simple to use integrating-averaging sound level meters, including instruments like the Pulsar Nova that quickly and clearly display when the Leq (or LAeq) has been reached by showing when the decibel level has settled in green on the OLED colour screen.
Furthermore, the PulsarAnalyzer software allows you to download your measurements and perform additional analysis and create a variety of reports. As with all of our products, our prime objective with the Nova is to provide the end user with a meter that does exactly what is required to perform a fully compliant noise survey. If you purchase the Nova product as a Measurement Kit, everything you require is provided in a high quality carry case giving you the confidence to know you have everything required to carry out your risk assessments.