Nr Noise Rating

Overview

Engineering reference data for Nr Noise Rating in acoustics.

Key Formulas

Speed of Sound

$c = \sqrt{\gamma R T}$

Speed of sound in an ideal gas.

Sound Level

$L = 10 \log_{10}(I/I_0)$

Decibel level.

Wavelength

$\lambda = c / f$

Wavelength = speed / frequency.

Variables

Symbol	Description	Unit
$c$	Speed of sound	m/s
$L$	Sound level	dB
$\lambda$	Wavelength	m
$f$	Frequency	Hz

Recommended NR Levels

Noise Rating Curves

The NR curves define the maximum allowable sound pressure levels across nine octave-band center frequencies for each Noise Rating level.

References

• Original Source