Audio Engineering

44 Chapter 2

2.6 Acoustic Intensity Level ( LI), Acoustic Power Level ( LW ), and

Acoustic Pressure Level ( LP )

2.6.1 Acoustic Intensity Level, L I

The acoustic intensity Ia (the acoustic power per unit of area—usually in W/m^2 or
W/cm^2 ) is found by

L

x

L

I

I











10

10

10 10

10

120

2

12 2

2

12 2

log

log.

W/m

W/m

W/m

W/m

dB. (2.23)

Table 2.3 : Equivalents of Pressure Levels

LP



20 1

0 00002

93 98

2

log. 2

.

N/m

N/m

dB

Older values of a similar nature are:

1 microbar  1/1,000,000 of atmospheric pressure

 7 4 d B

therefore

1 P a  10 dyn/cm^2

Other interesting fi gures:

Atmospheric pressure fully modulated LP  194 dB

1 lb/ft^2 LP  1 2 7. 6 d B

1 lb/in^2 LP  170.8 dB

50 lb of TNT measured at 10 ft LP  200 dB

12-inch cannon, 12 ft in front of and below muzzle LP

 220  d B

Courtesy of GenRad Handbook.