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