PTB Type Approval for the CR:171C optimus green sound level meterWe’re delighted to announce that the CR:171C Optimus Green Sound Level Meter has been granted Type Approval by the PTB in Germany.

In addition to these, we’ve recently received Type Approval to UNE-EN 61672 in Spain for the CR:161A, C:161B, CR:161C, CR:1710, CR:171A and CR:171B  instruments.

We’re also pleased to announce that the CR:161 series (CR:161A, CR:161B, CR:161C & CR:161D) now carry Type Approval in Serbia.

The CR:171C is currently the top of the optimus green range and includes all of the features of the other members of the optimus range as well as a set of new functions, including the ability to trigger audio recordings not just from level exceedences but from tonal noise and the rate of change of the noise.

This new approval adds to the existing PTB Type Approval for the Class 1 Optimus Sound Level Meters.

The following instruments now carry PTB Type Approval to IEC 61672 (DIN EN 61672):

  • CR:161A Class 1 Integrating Sound Level Meter
  • CR:161B Class 1 Data Logging Integrating Sound Level Meter
  • CR:161C Class 1 Data Logging Integrating Sound Level Meter with 1:1 Octave Band Filters
  • CR:1710 Class 1 Data Logging Environmental Sound Level Meter with Acoustic Fingerprint triggering
  • CR:171A Class 1 Data Logging Environmental Sound Level Meter with Acoustic Fingerprint triggering & 1:1 Octave Band Filters
  • CR:171B Class 1 Data Logging Environmental Sound Level Meter with Acoustic Fingerprint triggering with 1:1 & 1:3 Octave Band Filters
  • CR:171C  Class 1 Data Logging Environmental Sound Level Meter with Acoustic Fingerprint triggering, 1:1 & 1:3 Octave Band Filters, Extended Ln measurement and Tonal Noise Detection.

Find out more about the optimus green sound level meters. Continue reading »

Type Approval, or Pattern Approval, is a method where a recognised test laboratory, such as the PTB in Germany or LNE in France in the case of sound level meters, tests an instrument against a set of recognised and published standards to ensure that it meets the performance claims of the manufacturer.

The laboratory will test a number of samples of the product to check that they all meet the required standard. Once this has been completed and all of the samples have passed the tests, that particular model, or type, is approved and certified as meeting the claimed standards. Continue reading »


What is the Noise Doctor?

The Noise Doctor is a range of advice, products and support services put together by Cirrus Research, the experts in noise measurement instruments.

At Cirrus, we’re often asked questions such as:

“What is the best sound level meter for me to meet the Noise at Work Regulations?”,

“Why do I need to get my sound level meter calibrated?”

“Can I get training on using my sound level meter?”

The Noise Doctor is here to answer your questions and to help you find whatever you need.

Find out more about the Noise Doctor and ask your question on our website at or on our main website at

Follow the Noise Doctor on Twitter @TheNoiseDoc and see the Noise Doctor in action at the 2013 Safety & Health Expo, Stand F20.

Control of Noise at Work RegulationsWhat do the regulations require you to do?

The Control of Noise at Work Regulations 2005 require employers to prevent or reduce risks to health and safety from exposure to noise at work. Employees have duties under the Regulations too.

The Regulations require you as an employer to:

  • Assess the risks to your employees from noise at work
  • Take action to reduce the noise exposure that produces those risks
  • Provide your employees with hearing protection if you cannot reduce the noise exposure enough by using other methods
  • Make sure the legal limits on noise exposure are not exceeded
  • Provide your employees with information, instruction and training
  • Carry out health surveillance where there is a risk to health.

The Regulations do not apply to:

  • members of the public exposed to noise from their non-work activities, or making an informed choice to go to noisy places;
  • low-level noise that is a nuisance but causes no risk of hearing damage.

Employers in the music and entertainment sectors had until the 6th April 2008 to comply with the Noise Regulations 2005. They had to continue to comply with the Noise at Work Regulations 1989, which the 2005 Regulations replaced for all other workplaces. Continue reading »

676xnoisetoolsA new version of the NoiseTools software is now available for download.

This new version brings a number of new features and updates along with additional language options.

NoiseTools is compatible with the following:

  • Optimus Sound Level Meters
  • doseBadge Noise Dosimeter
  • Trojan Noise Nuisance Recorder
  • CR:260A Sound Level Meters
  • CR:800C Sound Level Meters

NoiseTools is also fully compatible with Windows 7 and Windows 8 and can be updated free of charge from the Cirrus website or through the auto-update features within NoiseTools itself.

The new version of NoiseTools is v1.4.5.

A Sound Level Meter with Calibrator

Sound Level Meter with CalibratorEach time you use your sound level meter, it should be calibrated using an acoustic calibrator. This can help you ensure that your instrument is measuring correctly and that you are complying with the requirements of any standards, regulations or guidelines that you are working to.

Most noise standards, regulations and guidelines require that your sound level meter is calibrated before it is used. If you don’t follow these requirements, any measurements that you make could be questioned and called into doubt. Continue reading »

optimus green sound level meter

With the recent snow that has hit the UK, Cirrus Research customers have raised a few questions about how wet weather and low temperatures could affect their noise measurements.

There are two situations surrounding the effects adverse weather has on noise measurements that can be looked at in more detail.  The first is based on if you are using a handheld sound level meter in low temperatures and the second is if you are using an outdoor measurement kit,  leaving your equipment outside in adverse weather conditions. Continue reading »

Please note that Acoustic Editor for Windows has been superseded by the NoiseTools program and the Noise-Hub software platform.

Please contact Cirrus Research plc if you would like more information about these current programs and the instruments that they support.

The NoiseTools software that is now provided, free of charge, with the optimus sound level meters, the doseBadge noise dosimeter as well as the CR:260A and CR:800C sound level meters, provides all of the functionality of the Acoustic Editor software in a single program.

The Cirrus noise monitors such as the CR:245 and CR:243 instruments are now supplied with the Noise-Hub platform which replaces Corvus and Acoustic Editor. Continue reading »

We’ve had a question that has been asked through our Blog form (the Do you have a questions box on the right) and the question is:

“How we can calculate average for a large data (e.g.24 hours data records of per second each) after downloading multiple files from the meter.

Simple averaging can be produced will not represent the level of energy of a record. For example, 45, 46, 48, 43, 78, 79, 71, 33, 55 levels, the simple arithmetic average would be 55.3.

But the energy level of noise for 78, 79 and 71 is high compared to other values so how can we calculate the average now?“.

This is an interesting question and one that we get asked quite frequently.

There are some applications where you would use a simple linear average to calculate a value from noise measurements but these are few and often very specific. Continue reading »

As we move into 2013, we’re looking forward to another busy year at Cirrus.

Throughout the year we’ll be presenting our sound level meters, noise dosimeters and environmental noise monitoring equipment at a number of trade shows and exhibitions and below is a list of those that we’re currently attending as an exhibitor.

If you’re planning on visiting any of these, let us know and we’d be pleased to see you.

IOSH 2013, February 26th 2013, Excel, London, UK

Safety & Health Expo, May 14th 2013, NEC, Birmingham, UK

AIHce , May 18th 2013, Montreal, Canada

ASSE 2013, June 24th 2013, Las Vegas, USA

Internoise 2013, September 15th 2013, Innsbruck, Austria

NSC Congress & Expo, September 30th 2013, Chicago, USA

These exhibitions are an ideal opportunity to meet with our sales team and to find out what’s new at Cirrus.

We’d also recommend that you subscribe to our blog as we’re about to start a new series of posts covering the most common noise terminology and parameters.

We’ve had a number of requests from both existing customers and visitors to our blog where they’ve asked us to explain what a particular term means or what a parameter on their instrument shows.

Over the next few months we’ll be covering the most common of these so if you’ve got any questions let us know and we can add it to the list! You can use the “Do you have a question” form on the right.

If you’d like to stay in touch with updates and news from Cirrus, just sign up for our newsletter using the form on the right side of this page, call us on 0845 230 2434 or email

From all of us at Cirrus, we would like to wish you a prosperous and successful 2013.

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