The value is 10-8 W/m2.
intensity level
intensity level
intensity level
If you think the threshold of pain is the sound intensity level of LI = 120 dB than you can convert that value to sound intensity I. Reference sound intensity Io = 10^−12 W/m² (Threshold of hearing). Reference sound intensity level LIo = 0 dB-SIL (Threshold of hearing level). Get sound intensity I when entering sound intensity level LI = 120 dB. Sound intensity I = Io×10^(LI/10) W/m² = 10^−12×10^(120/10) W/m² = 1 W/m².
Given: Sound intensity level LI1 = 40 dB and sound intensity level LI2 = 20 dB. Reference sound intensity Io = 10^−12 W/m² (Threshold of hearing) Reference sound intensity level LIo = 0 dB-SIL (Threshold of hearing level) Get sound intensity I1 when entering sound intensity level LI1 = 40 dB: Sound intensity I1 = Io×10^(LI/10) W/m² = 10^−12×10^(40/10) = 0.00000001 W/m² = 10^−8 W/m². Get sound intensity I2 when entering sound intensity level LI2 = 20 dB: Sound intensity I2 = Io×10^(LI/10) W/m² = 10^−12×10^(20/10) = 0.0000000001 W/m² = 10^−10 W/m². The sound intensity I1 = 10^−8 W/m² is 100 times more than the sound intensity I2 = 10^−10 W/m². The sound intensity level LI1 = 40 dB is 20 dB more than the sound intensity level LI2 = 20 dB.
The loudness has to do with the sound field quantity called sound pressure or sound pressure level (SPL). The sound intensity or acoustic intensity means the sound energy quantity.
That depends on the sound intesity level at the point of origen. Sound fall of with the square of the distance but the original intensity must be known.
Reference sound intensity Io = 10^−12 W/m² (Threshold of human hearing). Reference sound intensity level LIo = 0 dB-SIL (Threshold of human hearing intensity level). The sound intensity I is measured in watts per meter squared. The sound intensity LI level is measured in decibels (dB).
Given: Sound intensity level LI = 150 dB. Reference sound intensity Io = 10^−12 W/m² (Threshold of hearing) Reference sound intensity level LIo = 0 dB-SIL (Threshold of hearing level) Get sound intensity I when entering sound intensity level LI = 150 dB: I = Io×10^(LI/10) in W/m² = 10^−12×10^(150/10) = 1000 W/m².
You take a measuring microphone with a sound pressure level meter.
Sound power or sound intensity I is a sound energy quantity.Sound pressure p is a sound field quantity.Sound intensity is sound pressure squared. I = p².See related link.
Better think of the sound pressure, when you are listening. Sound pressure moves your ears and the diaphragm of the microphones. The sound intensity is very small. The level of 50 dB is equal to 0.0000001 W/m2 acoustic intensity. Scroll down to related links and look at "Conversion of sound units (levels)".