Page

**2**

Pressure squared:

ρc ≈ 400

I = p2 /ρc ρ = density

c = speed of sound

We define sound pressure level:

Lp = 20 log p/p0 p0 = 2 x 10-5 Pa (or N/m2)

(or SPL)

Slide 11

TYPICAL SOUND LEVELS

Slide 12

MULTIPLE SOURCES

Example:Two uncorrelated sources of 80 dB each will produce a sound level of 83dB

(Not 160 dB)

Slide 13

What we really want to add are mean-square

average pressures (average values of p2)

This is equivalent to adding intensities

Example: 3 sources of 50 dB each

Lp = 10 log [(P12+P22+P32)/P02] = 10 log (I1 + I2 + I3)/ I0)

= 10 log I1/I0 + 10 log 3 = 50 + 4.8 = 54.8 dB

Slide 14

Sound pressure level is measured with a sound level meter (SLM)

Sound intensity level is more difficult to measure, and it requires

more than one microphone

In a free field, however, LI LP

≈

Slide 15

Slide 16

Slide 17

Slide 18

Slide 19

Slide 20

Slide 21

Slide 22

Slide 23

Slide 24

Go to page:

1 2

1 2

- Acoustics of Concert Halls and Rooms
- The acoustic wave equation
- Sound pressure level
- Multiple sources
- Sound pressure and intensity

- The Effects of Radiation on Living Things
- Direct heat utilization of geothermal energy
- Newton’s Laws of Motion
- Newton’s law of universal gravitation
- Static and Kinetic Friction
- Space Radiation
- Thermal Energy

© 2010-2024 powerpoint presentations