NR - the Noise Rating Curve
The Noise Rating (NR) Curve used to determine acceptable indoor environments for hearing preservation, speech communication and annoyance.
The Noise Rating - NR - curves were first published in ISO Recommendation ISO/R 1996-1971 and is used to determine acceptable indoor environment for hearing preservation, speech communication and annoyance.
The noise rating graphs for different sound pressure levels are plotted at acceptable sound pressure levels at different frequencies. Acceptable sound pressure level vary with the room and the use of it. Different curves are obtained for each type of use. Each curve is obtained by a NR number.
Note! Noise Rating - NR - is commonly used in Europe. The Noise Criterion - NC - is more common in USA.
Recommended Noise Rating - NR - Levels
The Noise Rating level should not exceed the values listed below:
|NR 25||Concert halls, broadcasting and recording studios, churches|
|NR 30||Private dwellings, hospitals, theaters, cinemas, conference rooms|
|NR 35||Libraries, museums, court rooms, schools, hospitals operating theaters and wards, flats, hotels, executive offices|
|NR 40||Halls, corridors, cloakrooms, restaurants, night clubs, offices, shops|
|NR 45||Department stores, supermarkets, canteens, general offices|
|NR 50||Typing pools, offices with business machines|
|NR 60||Light engineering works|
|NR 70||Foundries, heavy engineering works|
Noise Rating Curves
|Maximum Sound Pressure Level (dB)|
- NR -
|Octave band mid-frequency (Hz)|
NR - Noise Rating Diagram
Download and print Noise Rating - NR - Chart
Related Mobile Apps from The Engineering ToolBox
- free apps for offline use on mobile devices.
Example - Estimating NR - Noise Rating
The sound pressure levels for different NR frequencies are measured to
- 31.5 Hz : 40 dB
- 62.5 Hz : 40 dB
- 125 Hz : 50 dB
- 250 Hz : 55 dB
- 500 Hz : 60 dB
- 1000 Hz : 50 dB
- 2000 Hz : 55 dB
- 4000 Hz : 45 dB
- 8000 Hz : 45 dB
The Noise Rating - NR - can be estimated as indicated in the spreadsheet diagram below to approximately
NR = 58 dB
Open the NR - Noise Rating example in your browser!
You can save and modify your own copy of the example above if you are signed into your Google Account.
Room acoustics and acoustic properties, decibel A, B and C, Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation.
• Noise and Attenuation
Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems.
NC - the Noise Criterion
Noise Criterion - NC - level is a standard uesd to describe the relative loudness of a space within a range of frequencies.
Noise Criterion (NC) - Free Online Calculator
Calculate Noise Criterion (NC) from octave band pressure levels.
Noise Criterion vs. Noise Rating and dB(A)
Comparing Noise Criterion (NC, NCB, RNC) to Noise Rating (NR) and dB(A).
Noise generated by Road Traffic
Estimate noise level generated by traffic.
Noise Rating (NR) - Free Online Calculator
An online Noise Rating (NR) calculator.
PNC - the Preferred Noise Criterion
A noise measurement system for continuous or ambient noise in indoor environments.
Preferred Noise Criterion (PNC) - Calculator
An online Preferred Noise Criterion (PNC) calculator.
Sound - Frequency, Wavelength and Octave
An introduction to the nature of sound with frequencies, wave-lengths and octaves.
Sound - Hearing Threshold vs. Age
Shift in hearing threshold for men and women vs. age.
Sound Intensity, Power and Pressure Levels
Introduction to decibel, sound power, intensity and pressure.
Sound Pressure is the force of sound on a surface perpendicular to the propagation of sound.
Ventilation Systems - Acoustic Calculation Procedure
Acoustic noise calculation procedure HVAC systems.