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Optimus Green - Environmental Noise Meter with 1/3 Octave Band Filters

Environmental Noise Meter
Environmental Noise Meter
Environmental Noise Meter Optimus Green Real-Time 1/3 Octaves

Price List

Class 1 Environmental Sound Level Meter with 1/3 Octaves
In stock

Noise Measurement Kit with Class 1 Environmental Meter with 1/3 Octaves, Calibrator and Case
In stock
Class 2 Environmental Sound Level Meter with 1/3 Octaves
In stock

Noise Measurement Kit with Class 2 Environmental Meter with 1/3 Octaves, Calibrator and Case
In stock
Class 2 Sound Level Calibrator
In stock

Class 1 Sound Level Calibrator
In stock
DC Output Cable - 18 pin to phono, 1 m
Lead time 1 week

RS232 Cable - 18 pin to 9 pin D female
Lead time 1 week

Microphone extension cable 2 m
Lead time 1 week

Microphone extension cable 5 m
Lead time 1 week

Microphone extension cable 10 m
Lead time 1 week

Microphone extension cable 20 m
Lead time 1 week

The delivery price is calculated during checkout based on your location and the goods ordered. Our basic delivery prices are:

Delivery within Netherlands, The: €27.00

Delivery Service: Three working days*

* For products that are in stock and the order received by midday.

Some products go through a final configuration and calibration before being shipped. If the calibration labs are busy this can add up to two days on to the delivery schedule but guarantees a fresh calibration.

Class 1 Environmental Sound Level Meter with 1/3 Octaves
In stock

Noise Measurement Kit with Class 1 Environmental Meter with 1/3 Octaves, Calibrator and Case
In stock


  • Audio recording
  • VoiceTag notes
  • Single measurement range 20 to 140 dB
  • Real-time 1/3 octave band filters
  • Weatherproof Outdoor Kit available
  • 15 Year Warranty


  • Environmental Noise Surveys
  • Mixed industrial and residential areas
  • Noise ordinance and community noise assessments
  • Tonal noise assessment

Measure All, Miss Nothing

The Optimus range of meters measure all parameters at the same time, so there is no need to spend time figuring out if you have the meter set up correctly before starting a measurement.

The Optimus Green sound level meter is available as either Class 1 or Class 2 - the most common for environmental noise measurement and more accurate being Class 1. This meter also has everything needed for occupational noise measurement in line with the Noise at Work regulations, making it ideal for anybody involved in both environmental (outside the factory) and occupational (inside the factory) noise.

Outdoor Kit Option

If the meter is to be left unattended in poor weather conditions then the optional Outdoor Kit should be used to offer protection against the elements.

The Outdoor Kit also includes a large rechargeable battery pack for at least seven days of monitoring.

Our Recommendation

noise measured outside
Use in Bright or Dark Conditions

Most environmental noise surveys demand the use of a Class 1 Sound Level Meter that can make repeating measurements, such as the 5 minute LAeq and L90 (background noise).

For environmental noise measurement with 1/3 octave band filters we recommend order code CK171B. Most regulations demand the use of a suitable Calibrator, which is included with this kit.

Nothing Tonal?

If you don't need to assess the tonal content of spectrum of the noise then please see the standard Optimus Green Sound Level Meter, which has all the environmental parameters but no additional filters.

Environmental Noise Measurements

The Optimus Green sound level meter is capable of measuring the noise parameters required for most environmental noise surveys. It is ideal for both short term and longer term measurement when installed in a weatherproof outdoor kit.

The main noise measurement parameters are:

  • Periodic LAeq and Ln (e.g. L10, L90, etc.)
  • Maximum and minimum sound levels
  • Time history
  • 1/1 Octave and 1/3 octave band spectrum
  • Noise Rating and Noise Criterion
  • Dates and times
  • Voice tag recording of notes
  • Audio recording

Simultaneous Parameters in a Single Span

To keep things sensible, the meter displays just the main parameters (Leq, Ln, etc.) on its display. However, it simultaneously measures all installed parameters, so you can sure of missing nothing. These parameters can be viewed on the display or, more usefully, after download.

The 1/3 octave band spectrum is measured and stored at the same time as the broadband measurement.

Noise Measurements Stored

The acoustic parameters stored can be logically separated into two groups:

1. Periodic Summary

Whenever you press Start and then Stop, you get a summary of the noise. For environmental surveys, the Start/Stop process is usually run automatically, repeating every 15 minutes for example. The summary typically consists of the following parameters describing the noise in detail:

  • LAeq (average sound level)
  • Ln values, including the all important L90 (background noise)
  • Lmin and Lmax (minimum and maximum sound levels)
  • Overall 1/3 octave band spectrum
  • Date, time and running time

2. Time History

The meter continually stores a number of parameters, typically every second, but the rate can be between 10ms and 2 seconds. When downloaded to a computer, this gives a detailed and very useful graph of the noise levels over time. A time history of 1/3 octave band spectra is also stored.

1/3 Octave Band Filters

This model of Optimus Green sound level meter is fitted with real-time 1/3 octave band filters. It is also fitted with 1/1 octave band filters and all these features apply to those too. 1/3 octave band filters are more common for environmental noise so these notes concentrate on that. The meter measures both 1/1/ octave and 1/3 at the same time, so both measurements are always available.

Summary Measurement

After a measurement is complete the overall spectrum is available to display or download to a computer. This shows the level in each of the bands over the whole measurement period.

Time History

As well as an overall summary, the meter stores a time history of the 1/3 octave band spectra. Using the software you can plot 3D charts and recalculate the summary spectrum over selected periods of the measurement.

Audio Recording

The audio recording feature is included with the Optimus Green sound level meter. If you choose to enable it the meter make a recording of the audio during the measurement. It's uses are:

  • Play back on the computer so you can identify the noise source
  • Further analysis of the noise using the Noise Tools software

The audio is stored along with the measurement, making playback and analysis more convenient. Depending upon the way you want to use the recording there are three levels of recording quality:

  • Standard Quality - acceptable quality for listening to
  • High Quality - for listening and post processing
  • Studio Quality - for high accuracy analysis

Audio recording can be started manually by pressing a key or it can be triggered automatically based on the level and duration of noise events.

VoiceTag™ - Audio Notes

The quickest way is to take notes about a measurement is to make a brief recording just before making a measurement. The VoiceTag stays with the measurement when it is transferred to the computer. The VoiceTag feature is included with all versions of the Optimus Green sound level meter.

Before starting a measurement, the meter will ask if you want to record a "VoiceTag". The meter will record any speech or the noise in question (to help you identify it later) for up to 30 seconds. This audio is transferred to the software automatically along with the measurement.

You can skip this stage if you don't need a voice tag, or the option can be disabled altogether.

When viewing the measurement on a computer the Play Voice Tag button lets you listen to the recording on the computer's speakers.

Environmental Noise Measurement

The Green version of the Optimus Sound Level Meter is ideal for almost any type of noise measurement, but it has been optimised for Environmental Noise Surveys. It provides all the parameters and features that are usually needed, and of course it meets the very demanding acoustic standard IEC 61672 to Class 1.

  • For environmental and community noise assessments
  • Ideal for BS4142, PPG24 and related regulations
  • Noise in mixed industrial and residential areas
  • Environmental noise surveys around factories

The following features are available with this meter, all designed to make the acoustic measurement process quicker, easier and more accurate:

  • Class 1 to IEC 61672, Type 1 to IEC 60651 and IEC 60804
  • Measurement of Leq, Ln (L90, etc) and many other parameters
  • Automatic, repeating measurements for longer term assessments

Calibration Check

calibration check
Calibration Check

Most regulations and measurement standards state that the meter's calibration should be checked before making measurements.

Fit the Calibrator over the microphone as shown on the right, switch it on and press the Calibrate button. The meter will automatically make any adjustments.

Calibration details are stored in the meter so that you can either make note or download them to a computer if you have the data logging option.

Manual Measurements

Press the Start key, shown on the right to begin the measurement process. If you have the data logging option fitted then the meter will ask if you want to make a Voice Tag recording.

The meter will start measuring the LAeq and other parameters that are needed for environmental noise surveys.

When you are happy that you have measured for long enough simply press the Stop key.

Recording Audio

The meter can record the audio - so you can listen to the actual sound later. Audio recordings can be started manually or when a trigger level is exceeded.

To start a recording manually press the Audio button during a measurement.

The Audio Recording can be set to start automatically when a certain level is exceeded. For example, you can set it to make a recording when the level exceeds 65dB(A). You can even set it to trigger when the trigger level is exceeded in just one band to detect tonal noise. Adjustable smoothing factors are available to avoid triggering on very short term noise.

Automatic, Repeating Measurements

For many environmental noise surveys, you need periodic (usually 5 minute, 15 minute or 1 hour) measurements showing values such as the Leq and the L90.

To make this type of measurement, use the Menu key to set the meter to make repeating measurements of the required duration. The meter will now run for the specified period. It will then stop, store the results and start again automatically.

It is better to mount the meter on a tripod for this type of measurement. A tripod mount is included on the back of the meter. It can be fitted to a standard camera tripod, or we can provide you with a suitable one.

For Data Logging Meters

The meters on this page include the NoiseTools software - there is no extra charge for this. You can download the software to evaluate it before making a purchase.

NoiseTools Software

The NoiseTools software runs on a Windows PC. It is compatible with all recent versions of Windows, from Windows 7 onwards.

  • Downloads measurements from the Optimus Sound Level Meter
  • Produce noise reports, including custom noise at work reports
  • Print or export reports for sharing
  • Listen to Voice Tags
  • Hearing protection selection reports
  • Link measurements to projects, people and places
  • Free, lifetime updates
  • Licence free with no installation restrictions

More information about NoiseTools

Optimus Green Options

The Optimus Green is already optimised for environmental noise surveys and so is adequate for most surveys without any additions.

The following decisions do need to be made

  • Class 1 or Class 2? - The most popular for environmental work is Class 1.
  • Calibrator - Most regulations state that you should have a calibrator.
  • Noise Measurement Kit - These include meter, calibrator and a carrying case.

Sound Level Calibrator

The most important of the accessories is the Calibrator. Most regulations state that you should use one to check the function of the meter before making any measurements.

Class 1 or Class 2?

A Class 1 sound level meter is a little more accurate than a Class 2 model. It is also more expensive. For most environmental noise measurements we recommend the use of a Class 1 meter, which gives better performance at higher frequencies and certainly looks better when presenting the results for legal purposes.

If you want a bit more information then please visit our FAQ page about Class / Type.

Noise Measurement Kit

The Noise Measurement Kits, order codes beginning CK..., include a sound level meter, calibrator of the correct class, software, carrying case and download cable. As a calibrator is generally needed for environmental noise, the Noise Measurement Kit is the most common way to buy the Optimus Green.

Weatherproof Outdoor Kit

The Optimus Outdoor Noise Measurement Kit is ideal when you need to leave the meter unattended in poor weather conditions. The sound level meter itself is not weatherproof and will be damaged by rainfall.

The Outdoor Kit includes a weatherproof carrying case, outdoor microphone system and a battery pack to offer at least seven days of measurement. An optional extra battery pack will give up to fourteen days of noise measurement.

Outdoor Microphone

If you need to measure outdoors but can mount the sound level meter indoors, or in a weatherproof enclosure with power, then the MK172 Outdoor Mic option adds this ability to this model sound level meter. It comes with a 10m microphone extension cable and can be mounted on a tripod or mast.

High Noise Levels - To 170 dB

With the standard microphone fitted, the Optimus will measure up to 140 dB (143 dB Peak). While this is adequate for almost all applications, there are occasions when it is necessary to go higher. Measuring gunshot and even extreme car sound systems can need more than the usual 140 dB limit.

With the MV200EH High Level Noise Mic System the Optimus Green can measure up to 170 dB.

StandardsIEC 61672-1:2013 Class 1 or Class 2
IEC 61672-1:2002 Class 1 or Class 2 Group XIEC
IEC 60651:2001 Type 1 I or Type 2 I
IEC 60804:2000 Type 1 or Type 2
IEC 61252:1993 Personal Sound Exposure Meters
ANSI S1.4 -1983 (R2006), ANSI S1.43 - 1997 (R2007)
ANSI S1.25:1991
1/1 and 1/3 Octave Band Filters to IEC 61260 & ANSI S1.11-2004
Measurement Range20dB to 140dB RMS Single Range
Noise Floor<18dB(A) Class 1, <21dB(A) Class 2
Frequency WeightingsRMS & Peak : A, C, & Z Measured Simultaneously
Frequency Bands10 x Octave Bands (31.5Hz to 16kHz)
36 x 1/3 Octave Bands (6.3Hz to 20kHz)
Time WeightingsFast, Slow & Impulse Measured Simultaneously
Memory8GB with 32GB factory fit option
Time History10ms, 62.5ms, 125ms, 250ms, 1/2 sec, 1 sec, 2 sec
VoiceTag AudioUp to 30 seconds of audio notes with each measurement
BluetoothBLE compatible with Android and iOS devices.
Mobile applications available from Google Play and the App Store
Audio RecordingOff, Manual, Threshold Triggered, Advanced Trigger
Studio Quality - 96kHz/32bit WAV format
High quality - 48kHz/24bit WAV format
Standard quality - 16kHz/16bit WAV format
Pre-Trigger function
Integrator Quick settingsEU, OSHA HC & OSHA NC, OSHA HC & ACGIH, MSHA HC & MSHA EC
Ln Statistical Values14 independent statistical Ln values calculated from 1/16th LAF
7 preset to L1.0, L5.0, L10.0, L50.0, L90.0, L95.0 & L99.0
Measurement controlManual, 1 min, 5 min, 10 min, 15 min,30 mins, 1 hour, Lden
Automatic Synchronisation & Repeat
Pause & Back Erase with user selectable duration
DimensionsSize: 283mm x 65mm x 30mm
Weight: 300gms/10oz
PowerBattery: 4 x AA Alkaline
Typically 12 hours with Alkaline AA
Typically 20 hours with Lithium AA Non-Rechargeable
ConnectionsUSB Type B to PC
AC & DC Output via ZL:174 (2 x Phono, 1m)
Multi-pin IO for external power via ZL:171 cable (2.1mm socket)
External Power: 5v-15v via MultiIO socket via ZL:171 cable (2.1mm socket)
CaseMaterial: High Impact ABS-PC with soft touch back & keypad
Tripod Mount1/4" Whitworth socket
EnvironmentalTemperature: Operating -10°C to +50°C, Storage -20°C to +60°C
Humidity: Up to 95% RH Non Condensing
ElectromagneticIEC 61672-1:2002 & IEC 61672-2:2003
IEC 61672-1:2013 & IEC 61672-2:2013
Except where modified by EN 61000-6-1:2007 & EN 61000-6-1:2007
Language optionsEnglish, French, German, Spanish.
Displayed FunctionsLXY, LXYMax, LXYMin, LXeq, LCPeak, LAPeak, LZPeak, LCeq-LAeq, LXE, LAIeq
Graph of Short LAeq, LCPeak
Integrators 2 & 3: TWA, Dose%, Est Dose%
Real-Time 1:1 Octave Bands (Graphical & Numeric)
Real-Time 1:3 Octave Bands (Graphical & Numeric)
Leq LF (20Hz to 200Hz)
Measurement Run Time
14 Statistical Ln values
Stored FunctionsLXYMax & Time History of LXYMax
LAeq, LCeq, LZeq, LCPeak, LZPeak, LAPeak, LAIeq
Time History of LAeq, LCeq, LZeq, LCPeak, LZPeak, LAPeak, LAIeq
Integrators 2 & 3: Lavg , TWA. %Dose
Time History of Lavg
1/1 and 1/3 Octave Bands:Overall Leq & Leq Time History for each band
Ln Values: 14 independent statistical values
Audio recording during measurement
where x=A ,C ,Z; y= F, S, I

Product Reviews - Optimus Green - Environmental Noise Meter with 1/3 Octave Band Filters

Review count: 1. Average rating: 5.0

★★★★★ 5 star rating

Verified NoiseMeters customer, Mon Jul 19 2021

The CK171B kit is an excellent product for my Environmental and Occupational noise measurement requirements along with the support received from Mike Bullen and team from NoiseMeters Ltd.

Niall O'Connell CARA EHS LTD

Reply Mon Jul 19 2021
Hi Niall, thank you for your review and comments. Best regards Mike


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