Outdoor Noise

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

Overview

Engineering reference data for Outdoor Noise 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 Day-Night sound level ( $L_{dn}$ ) is a 24-hour metric that accounts for the increased sensitivity to noise during nighttime hours. It applies a 10 dB penalty to sound levels measured between 10:00 PM and 7:00 AM.

The formula for calculating $L_{dn}$ is:

L_{dn} = 10 \log_{10} \left[ \frac{1}{24} \left( 15 \cdot 10^{L_d/10} + 9 \cdot 10^{(L_n + 10)/10} \right) ] \text{ (dB)}

Where:

$L_d$ is the equivalent sound level during daytime hours (7:00 AM to 10:00 PM).
$L_n$ is the equivalent sound level during nighttime hours (10:00 PM to 7:00 AM).