In residential areas most noise comes from transportation, construction, industrial, and human and animal sources. Road traffic noise is the major source of noise.
The noise can be highly variable. It is common that Day-Night sound levels - Ldn - in different areas may vary a range of 50 dB. The outdoor level - Ldn - in a wilderness areas may occur as low as 30-40 dBA compared to 85-90 dBA in a urban areas. Most urban dwellers lives in areas of Ldn more than 48 dBA.
The table below indicates common outdoor sound pressure levels in rural and urban environments at the different octave bands.
|Conditions||Octave Band Center Frequency (Hz)|
|Rural, no nearby traffic of concern||42||37||32||27||22||18||14||12|
|Suburban, no nearby traffic of concern||47||42||37||32||27||23||19||17|
|Urban, no nearby traffic of concern||52||47||42||37||32||28||24||22|
|Business or commercial area||57||52||47||42||37||33||29||27|
|Business or commercial area||62||57||52||47||42||38||34||32|
|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|
Room acoustics and acoustic properties, decibel A, B and C, Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation.
Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems.
Logarithmic unit used to describe ratios of signal levels - like power or intensity - to a reference level.
Acceptable noise - dBA - level at typical common locations.
Estimate noise level generated by traffic.
The transmission of outdoor sound through and around barriers - the Fresnel Number.
The propagation of outdoors sound vs. distance and attenuation.
Background noise frequencies that interferes with speech.
The EPA A-weighted sound level day and night equivalent definition - Ldn - for a 24 hour period.
Sound power from sources like fans, jet engines, cars, humans and more.