Outdoor Noise

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

outdoornoise

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).

Typical outdoor $L_{dn}$ ranges are:

Wilderness/Remote Areas: 30 - 40 dBA
Suburban/Residential Areas: 45 - 55 dBA
Urban Areas: 60 - 70 dBA
Busy Commercial/Industrial Corridors: 70 - 85+ dBA

Outdoor Sound Pressure Levels by Environment

The following table provides reference sound pressure levels across common octave band frequencies for various outdoor environments.

7 rows

Typical outdoor sound pressure levels (dB) at octave band center frequencies for various environmental conditions.
Condition	63(dB)	125(dB)	250(dB)	500(dB)	1000(dB)	2000(dB)	4000(dB)	8000(dB)
Night-time: Rural, no nearby traffic	42	37	32	27	22	18	14	12
Night-time: Suburban, no nearby traffic	47	42	37	32	27	23	19	17
Night-time: Urban, no nearby traffic	52	47	42	37	32	28	24	22
Night-time: Business or commercial area	57	52	47	42	37	33	29	27
Daytime: Business or commercial area	62	57	52	47	42	38	34	32
Daytime: Industrial or manufacturing area	67	62	57	52	47	43	39	37
Within 300 ft (91 m) of continuous heavy traffic	72	67	62	57	52	48	44	42