Sideway
output.to from Sideway
Draft for Information Only

Content

  Sound Power, W 
   Sound Power Level
   Sound Intensity, I
   Sound Intensity Level

Sound Power, W 

Sound power is another physical parameter of sound related to the rate of acoustic energy output  from a sound source. The unit of sound power is watt (W). Sound power is the total energy generation rate of a sound source, therefore the sound power of a sound source is not affected by the environment and remains a constant.

For example, a  higher power sound source always generated a high sound pressure than a lower power sound source at a given point of an environment. However, the sound pressure generated by a higher sound source may varies with location, time and environment. Some sound level measurement may even lower than that generated by the lower power sound source because teh acoustic pressure are highly depends on the surrounding environment.

So, Sound power is a measurement of the flow rate of acoustic energy and is independent from any point in space or time.

In general, the acoustic energy of a sound source passing through a small surface element as a given radius decreases as the distance increase. However, the integration of the energy of over the whole surface remains constant.

Although both sound pressure and sound power depends on the sound source. The reading of sound pressure also depends on the position of the receiver and are highly affected by the environment, such as shape and dimension of environment, interference with other sound sources etc. While the reading of sound power measures the sound source of an enclosed measuring surface and is not sensitive to the noise source outside the measuring surface. Therefore the sound pressure measurement can be used to measure the response of receiver and the sound power measurement can be used to identify the sound source of a noise. Besides, the measuring of sound pressure is much easier than the measuring of sound power.  

Sound Power Level

Similar to sound pressure, the range of sound power is also very wide, algorithmic scale is also defined. And a reference power of 10-12 is used. The sound power level is defined as:

image

where

LW is the sound pressure level
W is the sound power (W)
Wo is the reference sound power, 10-12watts (W)

The sound power of a sound source in term of sound power level is:

image

Sound Intensity, I

Sound intensity is defined as the sound power passing through a unit area.

image

where

I is sound intensity of source, W/m2
W is sound power of a source, W
A is surface area, m2

Sound intensity is not a property of sound source. But it is an important linkage between sound power and the measurable sound pressure.

For example, the average sound intensity of a free propagating plane wave can be expressed as the sound pressure as follows:

image.

where

I is sound intensity of source, W/m2
Prms is rms sound pressure
ρc is density of the medium
c is speed of sound in the medium

Sound Intensity Level

Similarly, the range of sound power is also very wide, algorithmic scale is also defined. And a reference intensity of 10-12 is used. The sound intensity level is defined as:

image.

where

LI is sound intensity level
I is sound intensity, W/m2
Io is the reference intensity, 10-12W/m2

With the reference intensity equals to 10-12W/m2, the sound intensity level, LI and the sound pressure level, Lp are numerically equal, that is LI=Lp.


©sideway

ID: 100900009 Last Updated: 9/7/2010 Revision: 0 Ref:

close

References

  1. Michael P. Norton; Denis G. Karczub,, 2003, Fundamentals of Noise and Vibration Analysis for Engieer
  2. G. Porges, 1977, Applied Acoustics
  3. Conrad J. Hemond, 1983, Engineering Acoustics & Noise Control
  4. F. Fahy, 2001, Foundations of Engineering Acoustics
close

Latest Updated LinksValid XHTML 1.0 Transitional Valid CSS!Nu Html Checker Firefox53 Chromena IExplorerna
IMAGE

Home 5

Business

Management

HBR 3

Information

Recreation

Hobbies 8

Culture

Chinese 1097

English 339

Reference 79

Computer

Hardware 249

Software

Application 213

Digitization 32

Latex 52

Manim 205

KB 1

Numeric 19

Programming

Web 289

Unicode 504

HTML 66

CSS 65

SVG 46

ASP.NET 270

OS 429

DeskTop 7

Python 72

Knowledge

Mathematics

Formulas 8

Algebra 84

Number Theory 206

Trigonometry 31

Geometry 34

Coordinate Geometry 2

Calculus 67

Complex Analysis 21

Engineering

Tables 8

Mechanical

Mechanics 1

Rigid Bodies

Statics 92

Dynamics 37

Fluid 5

Fluid Kinematics 5

Control

Process Control 1

Acoustics 19

FiniteElement 2

Natural Sciences

Matter 1

Electric 27

Biology 1

Geography 1


Copyright © 2000-2024 Sideway . All rights reserved Disclaimers last modified on 06 September 2019