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Optimus Green - Environmental Sound Level Meter

The Optimus Range
Overview Measurement Using It Software Options    

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.

  • Periodic LAeq and Ln (e.g. L10, L90, etc.)
  • Maximum and minimum sound levels
  • Time history (see below)
  • Dates and time
  • Real-time 1/3 octave band filters (option)
  • Voice tag recording
  • 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 be sure of missing nothing. These parameters can be viewed on the display or, more usefully, after download.

optimus sound level meter optimus yellow sound level meters optimus red sound level meter optimus green sound level meter optimus purple sound level meter
optimus range of sound level meters

Noise Measurements Stored

With 4GB of memory the Optimus has plenty of space to store thousands of measurements. 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)
  • Date, time and running time

Many other parameters are stored, but these are the more important ones.

2. Time History

On top of the summary data above, 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.

  noise profile time history
Time History Noise Profile

Although the Time History is not usually a requirement of the regulations, it is extremely useful when presenting a picture of the noise. It also offers the ability to zoom in on different times of day and recalculating the Leq for other time periods.

Real-Time Octave and 1/3 Octave Band Filters

All Optimus Green meters come fitted with real-time Octave Band Filters (1/3 octaves are available as an option). Octave Bands are ideal for basic analysis and are particularly useful for occupational noise assessments with hearing protector selection.

When assessing environmental noise with a tonal content, it is often necessary to make measurements in the 1/3 Octave Bands. The 1/3 Octave Band option provides real-time analysis from 6.3 Hz to 20 kHz.

Real-Time: The Optimus sound level meters have real-time filters, often called "parallel filters", so all bands are measured at the same time. This makes the meter much quicker and easier to use than one fitted with the older serial style filters.

Like the Time History store, the Octave or 1/3 Octave Band measurements are stored typically every second, giving a very detailed frequency analysis of the noise in question.

  1/3 Octave Band Leq  
  12.5Hz 20kHz  
  The Optimus Green stores
6.3Hz to 20kHz 1/3 Octaves

Voice Tag and Audio Recording

The quickest way to take notes about a measurement is to make a brief recording just before making a measurement. The Voice Tag stays with the measurement when it is transferred to the computer. With the Audio Recording feature, you can also choose to record the sound during measurement for playback on the computer or for more detailed analysis.

voice notes

The Voice Tag 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 "Voice Tag". 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.

audio playback

The Audio Record feature is included with all versions of the Optimus Green sound level meter. If you choose to enable it, the meter will make a recording of the audio during the measurement. Its 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 two levels of recording quality:

  • Standard Quality - a very good quality of recording for playback.
  • High Quality - an extremely high quality recording for playback and for further acoustic analysis.


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