Watch
Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made.
Favorite
Favoriting this resource allows you to save it in the “My Resources” tab of your account. There, you can easily access this resource later when you’re ready to customize it or assign it to your students.
Intensity
Sound Intensity is the power per unit area carried by a wave. Power is the rate that energy is transferred by a wave.
Learning Objectives

Identify SI and common technical units for sound intensity

Calculate sound intensity from power
Key Points

Sound intensity can be found from the following equation:
$I=\frac{{{\Delta}p}^2}{2\rho{v_w}}$ Δ p  change in pressure, or amplitude ρ  density of the material the sound is traveling through v_{w}  speed of observed sound. 
The larger your sound wave oscillation, the more intense your sound will be.

Although the units for sound intensity are technically watts per meter squared, it is much more common for it to be referred to as decibels, dB.
Terms

decibel
A common measure of sound intensity that is one tenth of a bel on the logarithmic intensity scale. It is defined as dB = 10 * log10(P 1/P 2), where P1 and P2 are the relative powers of the sound.

amplitude
The maximum absolute value of some quantity that varies.
Examples

Use the following information to calculate (1) the sound intensity and (2) the decibel level. p = 0.656 Pav_{w}= 331 m/s^{2}, at 0 degrees Celsius. (Air pressure at 0C is 1.29 kg/m^{3})1.
$I=\frac{{\Delta}p{^2}}{2\rho{v_w}}\\ I=\frac{{{0.656 Pa}^2}}{2*1.29{\frac {kg}{m^3}}*331{\frac ms}}\\ I=5.04*10^{4} \frac W{m^2}$ 2. Now we want to convert this intensity into decibel level:$\beta = 10 log_{10}\frac {5.04*10^{4}}{1*10^(12)}\\ \beta = 10 log_{10}5.04*10^8\\ \beta = 10*8.70dB\\ \beta = 87dB$
Full Text
Overview of Intensity
Sound Intensity is the power per unit area carried by a wave . Power is the rate that energy is transferred by a wave.
The equation used to calculate this intensity, I, is:
Sound Intensity
Sound intensity can be found from the following equation:
Although the units for sound intensity are technically watts per meter squared, it is much more common for it to be referred to as decibels, dB.
A decibel is a ratio of the observed amplitude, or intensity level to a reference, which is 0 dB.
The equation for this is:
For a reference point on intensity levels, below are a list of a few different intensities:
Assign just this concept or entire chapters to your class for free.
Key Term Reference
 Pressure
 Appears in this related concepts: SI Units of Pressure, Physics and Engineering: Fluid Pressure and Force, and Surface Tension and Capillary Action
 SI units
 Appears in this related concepts: Time, Length, and Problem Solving
 atom
 Appears in this related concepts: John Dalton and Atomic Theory, Atomic Theory of Matter, and Overview of Atomic Structure
 eardrum
 Appears in this related concept: Human Perception of Sound
 energy
 Appears in this related concepts: Surface Tension, Introduction to Work and Energy, and The Role of Energy and Metabolism
 equation
 Appears in this related concepts: A General Approach, Equations and Inequalities, and Equations and Their Solutions
 normal
 Appears in this related concepts: Vectors in the Plane, Arc Length and Curvature, and Normal Forces
 power
 Appears in this related concepts: Weber's View of Stratification, Authority, and Power
 watt
 Appears in this related concepts: Energy Usage, What is Power?, and Convection
 wave
 Appears in this related concepts: Waves, Properties of Waves and Light, and Other Forms of Energy
Sources
Boundless vets and curates highquality, openly licensed content from around the Internet. This particular resource used the following sources:
Cite This Source
Source: Boundless. “Intensity.” Boundless Physics. Boundless, 03 Jul. 2014. Retrieved 20 May. 2015 from https://www.boundless.com/physics/textbooks/boundlessphysicstextbook/sound16/soundintensityandlevel129/intensity4586077/