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Intensity
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Sound Intensity is the power per unit area carried by a wave. Power is the rate that energy is transferred by a wave.
Learning Objective

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.
Example
 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:
Sound Intensity
Graphs of the gauge pressures in two sound waves of different intensities. The more intense sound is produced by a source that has largeramplitude oscillations and has greater pressure maxima and minima. Because pressures are higher in the greaterintensity sound, it can exert larger forces on the objects it encounters
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:
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Key Term Reference
 Pressure
 Appears in these related concepts: SI Units of Pressure, Physics and Engineering: Fluid Pressure and Force, and Surface Tension and Capillary Action
 SI units
 Appears in these related concepts: Time, Length, and Problem Solving
 atom
 Appears in these related concepts: Overview of Atomic Structure, Description of the Hydrogen Atom, and Stable Isotopes
 eardrum
 Appears in this related concept: Human Perception of Sound
 energy
 Appears in these related concepts: Surface Tension, Energy Transportation, and Introduction to Work and Energy
 equation
 Appears in these related concepts: Equations and Inequalities, Graphs of Equations as Graphs of Solutions, and What is an Equation?
 normal
 Appears in these related concepts: Vectors in the Plane, Arc Length and Curvature, and Normal Forces
 power
 Appears in these related concepts: Force of Muscle Contraction, What is Power?, and Authority
 watt
 Appears in these related concepts: Energy Usage, Convection, and Isotherms
 wave
 Appears in these related concepts: Properties of Waves and Light, Waves, and Atomic Structure
Sources
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Cite This Source
Source: Boundless. “Intensity.” Boundless Physics Boundless, 26 May. 2016. Retrieved 22 Feb. 2017 from https://www.boundless.com/physics/textbooks/boundlessphysicstextbook/sound16/soundintensityandlevel129/intensity4586077/