The Environmental Protection Agency - EPA - has adopted a system of four "sound descriptors"
- A-weighted sound level
- Sound Exposure Level - Ls
- Equivalent Sound Level - Leq
- Day-Night Sound Level - Ldn
to summarize how sound is heard and measured and to determine the impact of noise on health and welfare.
Day-Night Sound Level - Ldn
is the A-weighted equivalent sound level for a 24 hour period with an additional 10 dB imposed on the equivalent sound levels for night time hours of 10 pm (22) to 7 am (07).
Day-Night Sound Level can be expressed as
Ldn = 10 log (1 / 24 (15 (10Ld/10) + 9 (10((Ln + 10)/10))) (1)
Ldn = day-night sound level (dBA)
Ld = daytime equivalent sound level (dBA)
Ln = nighttime equivalent sound level (dBA)
Examples of typical outdoor Day-Night Average Sound at various locations:
|Apartment next to freeway||87|
|3/4 mile from runway at major airport||86|
|Downtown with construction activity||79|
|Old urban residential area||59|
|Agricultural crop land||44|
Example - Day-Night Sound Level
The equivalent daytime sound level is 70 dB and the equivalent nighttime sound level is 50 dB. The Day-Night sound level can be calculated as
Ldn = 10 log (1 / 24 (15 (10(70 dB)/10) + 9 (10((50 dB)+ 10)/10))
= 68.2 dB
Day-Night Sound Level Calculator
Use the calculator below to calculate EPA 24 hour Day-Night sound level.
Ld - daytime equivalent sound level (dB)
daytime hours (h)
Ln - nighttime equivalent sound level (dB)
nighttime hours (h)
Room acoustics and acoustic properties, decibel A, B and C, Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation.
Acceptable noise - dBA - level at typical common locations.
The noise level should not exceed certain values to protect public health and welfare.
Outdoor ambient sound pressure levels (dBA) in rural and urban business and industrial environments with or without limited traffic.
The phonetic alphabet used in international aircraft communications.
The propagation of outdoors sound vs. distance and attenuation.
The EPA Equivalent Sound Level - Leq - quantifies the noise environment to a single value of sound level for any desired duration.
The EPA Sound Exposure Level - Ls - describes the noise from a variable source.
OSHA maximum A-weighted sound pressure levels allowed per day.