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Featured Content

Celebrate the 40th Anniversary of the Institute of Acoustics

Celebrate the 40th Anniversary of the Institute of Acoustics

Cirrus Research is proud to be a Key Sponsor of the Institute of Acoustics, the UK’s professional body for those working in acoustics, noise and vibration and this week we’re celebrating the 40th Anniversary of the Institute at the annual conference at the NEC, Birmingham. Cirrus has been involved with the Institute of Acoustics, or IOA, Read More »
Noise level measured with 1:3 Octave Band Filters

What are Octave and Third Octave Band Filters on a Sound Level Meter?

When more detailed information about a complex sound is needed, the frequency range of 20Hz to 20kHz can be split into sections or bands. This is done electronically within a sound level meter.

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blurred man with optimus

What’s the Difference Between a Class 1 and Class 2 Sound Level Meter?

We’ve covered the differences between Class and Type in sound level meter standards in a previous post and so in this post we’ll cover the differences between a Class 1 and a Class 2 sound level meter.

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Product Updates


NoiseTools is now compatible with Windows 8.

A new version of the NoiseTools software is available that is compatible with the new Windows 8 operating system.
Version 1.4.4 of NoiseTools can be downloaded from the Cirrus website or updated from within NoiseTools itself.

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PTB Type Approval for the optimus sound level meters

We are delighted to announce that the optimus red and optimus green sound level meters have been Type Approved by the PTB in Germany!

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Tonal noise analysis with the optimus green sound level meters

Often the sound energy from a noise source will be spread over a wide band of frequencies. Sometimes a noise source will emit noise that is concentrated in a narrow part of the spectrum or contains a high proportion of energy at a single frequency (a “pure tone”).  This is referred to as tonal noise.

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