# What is Intensity?

Intensity:

The rate of flow of sound energy through unit area placed normal to the direction of propagation of sound is called intensity. Intensity of a sound determines its loudness.

Characteristics of intensity are:

• Amplitude: Intensity is directly proportional to the square of the amplitude of the wave. If I be the intensity and A be the amplitude,

then I∝A2.

• Frequency: Intensity varies directly as the square of the frequency of the sound If I be the intensity and f be the frequency,

then I∝f2.

• Distance of the source from the receiver: Intensity decreases with increases the If I be the intensity and r be the distance of the source from the receiver.

then I∝1/r2

• Density of the medium: Intensity is directly proportional to the density of the medium.

i.e. I∝ρ; where ρ is the density of the medium.

• Size of the source: Greater is the size of the source, greater will be the intensity of sound emitted from it.

Unit of Intensity:

Unit of Energy = Joule (J)
Unit of Area = m²
Unit of Time = second (s)

So, Unit of Intensity (I) = J/m²s = watt/m² = wm-2