Optimus Red - Sound Level Meter with NR and NC Calculation

Noise Rating

Commonly used in Europe, the noise rating value is generally used for assessing the indoor noise levels, often in connection with air conditioning units and similar indoor equipment. Some example applications along with typical NR levels are:

• NR 25 - Concert hall, studio, church
• NR 30 - Home, hospital, cinema
• NR 35 - Library, school, hotel, quiet office
• NR 40 - Corridor, cloakroom, restaurant, office
• NR 45 - Department store, supermarket, busy office
• NR 50 - Typing pool, office with business machines
• NR 60 - Light engineering works
• NR 70 - Heavy engineering works

Calculating Noise Rating

The sound level meter carries out all the calculations for you. NR calculations are carried out from the octave band measurement results. The octave band measurements are compared with the standard Noise Rating Curves. The NR value is the lowest NR curve that is not exceeded by any of the octave band measurements.

Noise Rating Example Calculation

The NR calculation process is better shown on a chart. This shows an example for explanation purposes, it is not a screen image from the Optimus sound level meter.

The blue bars show the octave band measurements. The red lines are the standard noise rating curves. This example would return a noise rating value of 85 dB.

Noise Criterion

Commonly used in the US, the noise criterion value is for assessing the indoor noise levels, often in connection with air conditioning units and similar indoor equipment. Some example applications along with typical NC levels are:

• NC 25 to 30 - Private home, quite office, school
• NC 30 to 35 - Courtroom, hospital
• NC 35 to 40 - Corridor, lobby, open-plan offices, library
• NC 40 to 45 - Service & support areas, busy office, restaurant
• NC 45 to 65 - Factory, sports center

Calculating Noise Criterion

The sound level meter carries out all the calculations for you. NC calculations are carried out from the octave band measurement results. The octave band measurements are compared with the standard Noise Criterion Curves. The NC value is the lowest NC curve that is not exceeded by any of the octave band measurements.

Noise Criterion Example Calculation

The NC calculation process is better shown on a chart. This shows an example for explanation purposes, it is not a screen image from the Optimus sound level meter.

The blue bars show the octave band measurements. The red lines are the standard noise criterion curves. This example would return a noise criterion value of 62 dB.

For Data Logging Meters

This meter and the noise measurement kits 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 Red
• Produce noise reports, including NR/NC reports
• Print or export reports for sharing
• Listen to Voice Tags
• Hearing protection selection reports
• Select suitable hearing protectors
• Link measurements to projects, people and places
• Free, lifetime updates
• Licence free with no installation restrictions

More information about NoiseTools

Optimus Red Options

There are not too many options for this version of the Optimus Red sound level meter as most are included. It includes all the parameters that you need for occupational noise measurements in line with the regulations and directives. It also has real-time octave band filters fitted and comes with data logging and the NoiseTools software.

The main options are:

• Class 1 or Class 2? - Most occupational noise regulations say Class 2 is adequate.
• Calibrator - The noise at work 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. The regulations state that you should use one to check the function of the meter before and after 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. If you are using the meter exclusively for occupational noise measurements then the regulations are quite clear: Class 2 is adequate. For this reason we recommend the Class 2 model.

However, if you need to make other noise measurements, such as noise emitting from your factory into the local environment, then it might be wise to go for a Class 1 meter. In these instances the local authority (Environmental Health Officer for example) will usually expect measurements made with a Class 1 meter.

Noise Measurement Kit

The Noise Measurement Kits, order codes CK162D and CK161D, include a sound level meter (with octave bands and NR/NC calculations), calibrator of the correct class, software, carrying case and download cable.