Cambridge Encyclopedia :: Cambridge Encyclopedia Vol. 71

sound intensity level

Symbol LI, units db (decibel); noise level relative to the faintest audible sound, which is rated as 0 db. It is related to sound intensity I, units W/m2, the power per unit area of the sound wave. LI = 10 log(I/Io), where Io is taken to be 10?12 W/m2, the sound intensity corresponding to 0 db. A whisper has a typical sound intensity level of 20 db; a conversation of 50 db; a busy street of 70 db; heavy machinery of 90 db; and jet aircraft of 120 db.

Sound measurements
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


Sound intensity level or acoustic intensity level is a logarithmic measure of the sound intensity in comparison to the reference level of 0 dB (decibels).

User Comments Add a comment…

The Sound - Speed of sound, Sound pressure, Sound pressure level, Measurement of sound [next] [back] sound film - History, Consequences