Measurement
Sound pressure can be measured directly using a microphone. Particle velocity can be measured directly using a particle velocity probe. It is also possible to measure the quantities indirectly using the opposite instrument. Sound intensity can be measured using different combinations:
- Microphone and particle velocity probe (p-u probe)
- Two microphones (p-p probe)
- Two particle velocity probes (u-u probe)
The sound pressure is measured in pascal, the particle velocity in meters per second and the sound intensity in watts. Often these quantities are measured as a level in decibels relative to a certain quantity.
The sound pressure level is given by
where
- is the root-mean square pressure in Pa
- is the reference value of 2*10-5 Pa
The particle velocity level is given by
where
- is the root-mean square particle velocity in m/s
- is the reference value of 5*10-8 m/s
The sound intensity level is given by
where
- is the root-mean square sound intensity in W
- is the reference value of 1*10-12 W
Read more about this topic: Acoustic Wave
Famous quotes containing the word measurement:
“That’s the great danger of sectarian opinions, they always accept the formulas of past events as useful for the measurement of future events and they never are, if you have high standards of accuracy.”
—John Dos Passos (1896–1970)