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|Sound pressure p|
|Sound pressure level (SPL)|
|Particle velocity v|
|Particle velocity level (SVL)|
|(Sound velocity level)|
|Particle displacement ξ|
|Sound intensity I|
|Sound intensity level (SIL)|
|Sound power Pac|
|Sound power level (SWL)|
|Sound energy density E|
|Sound energy flux q|
|Acoustic impedance Z|
|Speed of sound c|
The measure of a ratio of two sound powers is
- P1, P0 are the sound powers.
The sound power level PWL, LW, or LPac of a source is expressed in decibels (dB) and is equal to 10 times the logarithm to the base 10 of the ratio of the sound power of the source to a reference sound power. It is thus a logarithmic measure.
The reference sound power in air is normally taken to be 10−12 watt = 0 dB SWL.
Sound power is neither room dependent nor distance dependent, like it is with sound pressure or sound intensity. Sound power belongs strictly to the sound source.
Table: Sound power and sound power level of some sound sources Edit
dB re 10−12 W
Rocket engine 1,000,000 W 180 dB Turbojet engine 10,000 W 160 dB Siren 1,000 W 150 dB Heavy truck engine or
loudspeaker rock concert
100 W 140 dB Machine gun 10 W 130 dB Jackhammer 1 W 120 dB Excavator, trumpet 0.3 W 115 dB Chain saw 0.1 W 110 dB Helicopter 0.01 W 100 dB Loud speech,
0.001 W 90 dB Usual talking,
10−5 W 70 dB Refrigerator 10−7 W 50 dB (Auditory threshold) 10−12 W 0 dB
Usable music sound (trumpet) and noise sound (excavator) both have the same sound power of 0.3 watts, but will be judged psychoacoustically to be different levels.
Sound power with plain sound wavesEdit
Between sound power and other important acoustic values there is the following relationship:
|c||m/s||speed of sound|
|ω = 2πf||rad/s||angular frequency|
|ρ||kg/m3||density of air|
|Z = c · ρ||N·s/m³||acoustic impedance|
|E||W·s/m³||sound energy density|
|Pac||W||sound power or acoustic power|
- Ohm's law as acoustic equivalent — calculations
- Relationships of acoustic quantities associated with a plane progressive acoustic sound wave — pdf
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