Noise Criteria

Reference data and engineering information about noise criteria for acoustics applications.

Overview

Engineering reference data for Noise Criteria in acoustics.

Key Formulas

Speed of Sound

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

Speed of sound in an ideal gas.

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

The dB(A) scale, or A-weighted sound pressure level ( $L_A$ ), is a single-number rating that approximates the relative loudness perceived by the human ear. It is derived by applying a specific frequency-weighting curve (the A-weighting network) to the measured sound spectrum, which attenuates low and very high frequencies to reflect human hearing sensitivity.

This makes dB(A) a practical and widely used metric for assessing environmental and industrial noise. It is commonly specified in noise ordinances and equipment ratings, but it does not provide the same frequency-specific detail as spectrum-based criteria like NC or NR.

References

Original Source