Sound amplification or loudness is measured in decibels (dB). The threshold of human hearing is approximately 6 dB at 1000 Hz and increases with decreasing frequency. (approximately 25 dB at 63Hz)
Noise is any unwanted sound. Noise may be continuous or intermittent based on the source.
Noise measurements are taken in the audible sound spectrum and defined as center octave bands consisting of:
|Jet Engine||160||Hearing Damage|
|Threshold of Pain||140|
|Threshold of Feeling||120|
|OSHA Limit||90||8 Hour Exposure|
A decibel (dB) level is measured in each octave band at a known distance, the decibel levels are combined logarithmically on an energy basis to give an overall level. The decibel level is typically measured in sound pressure level – (SPL), or sound power level – (PWL).
Sound Power Level (PWL) is a measure of total acoustic power or potential, similar to the watt rating of a light bulb.Sound Pressure Level (SPL) is a measure of the actual acoustic effect due to distance and other mitigating factors. Sound Pressure (SPL) is what we hear, caused by Sound Power (PWL) emitted from the source.