The Ultimate Sound Meter Buyer’s Guide


If you need to measure sound, then you may be faced with a daunting array of options and equipment variations. This guide is designed to highlight some of the more important choices you need to make depending on what you are doing.


The use to which you are putting a sound meter will affect the choice of some of the features, so it is important to understand what you will be using the equipment for.

  • Health and Safety – for compliance with the Control of Noise at Work Regulations 2005.
  • Environmental assessments – this might be for neighbourhood complaints, planning assessment or environmental permit compliance.
  • Construction noise – this is often a combination of health and safety and environmental features.
  • Room acoustics – for assessing the sound performance of buildings.
  • High-level noise sources – such as gunshots or explosions.
  • Fire alarm testing.
  • Audiometer Booth Testing – checking for the suitability to carry out hearing tests in a booth or room.

Health and Safety

Handheld Sound Meters

To comply with the Control of Noise at Work Regulations 2005, you need a minimum of three measurements.

  • LAeq,T – The equivalent continuous ‘A’ weighted sound level over the measurement time, T
  • LCpeak – The ‘C’ weighted instantaneous peak pressure of a single event (for detecting loud bangs or impacts)
  • LCeq,T – The equivalent continuous ‘C’ weighted sound level over the measurement time, T

So long as the equipment can measure all of these at the same time, then you will be able to do everything you need to.

The LCeq,T is used to assess the suitability of hearing protection according to its attenuation data and there is an option to include 1/1 Otave bands on your sound meter, which will allow you to improve the accuracy of those hearing protector assessments.

As most noise at work surveys are carried out using a hand-held sound meter, then you don’t usually need any other features such as data-logging as you will be there for the measurement.

The Castle dBair is in its element in this setting, with in-built hearing protection database, octave bands and ultra-simple to use. This is what it was built for.


As an alternative to a hand-held sound meter, particularly where an employee is mobile, it is possible to use a dosemeter (or dosimeter), which is mounted on the person with a microphone near the ear. Dosemeters are only required to give you the LAeq,T although many now provide other data such as the ‘C’ weighted level and the LCpeak. You can even get dosemeters now with octave bands!

Modern dosemeters like this one are full of features including the ability to talk to a mobile app.

Environmental Assessments

Before purchasing a sound meter for environmental assessments, it is very important to understand the standard or guidance you need to comply with. The equipment requirements will be very different if you are trying to meet a local authority planning condition compared with a full BS4142 assessment.

Each standard will give you the parameters needed to comply. Here are some examples.

Planning Condition

Often a planning condition supplied by a local authority will be stated in terms of the 1-hour LAeq levels. If this is the case, then you simply need a sound meter capable of recording the LAeq  every hour and that’s it. If you are leaving the equipment outdoors, you will need a weather-proofing solution for the instrument and the microphone, but these can be obtained without breaking the bank. Do beware as some planning departments can add more complex clauses to the conditions, so it’s always best to check.

For simple site boundary monitoring, you can use a SONUS sound meter in a weatherproof enclosure as found here.

For live data collection in the cloud, you can use an E-Box LIVE such as this one.

BS4142 Assessment

This is a very specific standard relating to the noise from commercial premises and its effect on nearby residential areas. To carry out BS4142 assessment you need as a minimum:

  • LAeq, 15-minute – The equivalent continuous ‘A’ weighted sound level over each 15-minute period.
  • LAeq, 1-hour – The equivalent continuous ‘A’ weighted sound level over each 1-hour period.
  • LA90, 1-hour – the sound level that is exceeded for 90% of the measurement time.

If you want to carry out the further test for tonality, then you will also need 1/3 octave bands or even FFT (Fast Fourier Transform).

Impulsivity can also be optionally measured, and this will usually require a special feature in the sound meter or its accompanying software.

BS4142 assessments do not require huge amounts of data or complex sound parameters, so the system you need to collect the data does not need to be overly complex. The E-Box LITE with a SONIK sound meter will do everything you need without breaking the bank.

Remote Monitoring

Some environmental applications require you to leave a sound meter outdoors for extended periods of time, which can be achieved by putting the sound meter in a special weatherproof box, usually with a battery and possibly a solar panel. The microphone will then need a protective covering and then the whole thing can be left to the elements.

If it is a particularly sensitive situation, then it may be a requirement that you are notified whenever the sound exceeds a pre-determined level. In this case, you will need the addition of a modem, which can send data to a website, which will then send alerts to your mobile phone or email. There is a separate article on how to set up these triggers and alerts.

The E-Box LIVE system with a dBair sound meter at its core will provide everything you need for this type of environmental monitoring. It can be used with solar panels to extend the battery life almost indefinitely.

Construction Noise

If you work on a construction site and have responsibility for noise assessments, this could well include both health and safety and environmental measurements. This is because the standard used in construction is BS5228, which covers both noise and vibration and in each, the safety of workers as well as the environmental impact of the site. If this is the case, then you are likely to need a combination of the features, including.

  • LAeq,T – The equivalent continuous ‘A’ weighted sound level over the measurement time, T
  • LCpeak – The ‘C’ weighted instantaneous peak pressure of a single event (for detecting loud bangs or impacts)
  • LCeq,T – The equivalent continuous ‘C’ weighted sound level over the measurement time, T
  • Data-logging to capture the LAeq,T values periodically.
  • 1/1 and/or 1/3 Octave bands to deal with hearing protection and tonality in environmental noise.
  • Weatherproofing in case you need to carry out extended boundary monitoring for planning compliance.

The Castle dBAir can be used for many applications, including construction site monitoring and can be upgraded later to include weatherproofing and live data communication.

Room Acoustics

The acoustic performance of indoor spaces is quite a large and involved subject and requires some specialist equipment as well as special measurement parameters. While it would be unwise to carry out a full room or auditorium survey without the right training, there are simpler versions of some of the tests, that allow you to get the basics. The features you might look out for in a sound meter, on top of the basic Leq  metrics could be.

  • Reverberation Time (RT60) – this measure the echo in a room and does require something to make a loud sound with.
  • NR or NC curves – these allow assessment of certain activities that might take place in a type of room.
  • Speech Intelligibility – although this does require quite a lot of other equipment.

To carry out more in-depth room acoustics surveys, you might need some or all the following equipment.

  • Cabinet or Dodecahedron speaker system.
  • Amplifier and tone generator.
  • Tapping machine for structure borne transmission.
  • 2 synchronised sound meters for airborne transmission measurements.
  • Software to process the data post-measurement.

For a room acoustics setup, give us a call at Castle to discuss the best solution for you.

High Level Noise Sources

Some applications simply create too much sound for most standard sound meters to cope with.

  • Gunshot
  • Fireworks
  • Custom Car Stereo’s at full volume

Such applications are fairly specialised and require a modified sound meter with a special microphone and a different calibration setting. You will need to make sure your sound meter is capable of accepting a high-level microphone. These are often smaller in diameter too.

If you need to carry out this type of testing, then please get in touch with the team at Castle for a quotation.

Fire Alarm Testing

Whether installed in residential or commercial properties, fire alarms should be tested periodically according to BS 5839:2017. This should include a noise test to ensure that the alarm is at least 5dB above ambient levels anywhere in the property and at least 65dB as well as being at least 75dB at the bed head for sleeping residents.

The sound meter should comply with the following.

  • At least Class 2 to IEC 61672.
  • Have ‘A’ weighted maximum sound level ().
  • Have ‘SLOW’ time constant.
  • Have a calibrator for daily calibration check.

The Castle SONUS B is a basic class 2 sound meter that complies with the standard at a budget price.

The Castle SONIK S class 2 sound meter has the added benefit of data-logging, so you can store the results if you are testing multiple alarms –

Audiometer Booth Testing

Testing someone’s hearing usually means playing a series of very quiet tones into their ears through a pair of headphones and asking them to press a button when they hear the sound. To do this effectively means the background should be relatively quiet.

ISO 8253 gives guidance on maximum levels in 1/3 octave bands, with some numbers that are quite difficult to achieve. It also means you will need a sound level meter with 1/3 octave bands and the capability to measure at very low levels.

The British Society of Audiology (BSA) as issued guidance for people who do not have such capability and perhaps are only doing health surveillance rather than clinical hearing checks. The BSA states that levels should be below 35dBA. You must make sure that any sound meter you use for this purpose can measure that low, as many are not.

The following equipment can be used for testing audiometric environments.

The Castle SONUS E –

The Castle SONIK E –

The Castle dBAir with 1/3 Octave Band option –

The Svantek SV977D with 1/3 Octave Bands –

a part of the Castle Group of websites

Tel: 01723 584250
Mailing List
Google Plus
Follow Us