Sound Intensity Formula

The Formula for sound intensity is expressed as

\(\begin{array}{l}I=\frac{P}{A}\end{array} \)

Where

P = sound power

A = area

In order to measure the sound intensity level, need to compare the given sound intensity value with standard intensity value.

The formula of Sound Intensity Level is expressed as

Where

I = sound intensity and

Io = reference intensity

The unit of sound intensity is expressed in decibels (dB)

Solved examples on Sound Intensity

Example 1

A person whistles with the power of 0.9 × 10^-4 W. Calculate the sound intensity at a distance of 7m.

Solution:

Given

P = 0.9 × 10^-4 W

A = 7m

Sound intensity formula is

I = P / A

I = 0.9×10⁻⁴ / 7

I = 1.28 x 10^-5 W/m²

Example 2

Determine the intensity level which is equivalent to an intensity 1 nW/m².

Solution:

Intensity Level formula is given by

IL = 10 log₁₀ I / I₀

Here

I = 1 nWm-2 = 1 × 10^-9 Wm^–2

I_o = 10^-12 Wm^-2

I_L= 10 log₁₀ (1×10⁻⁹) / 10⁻¹²

I_L = 10 log₁₀ 10³

I_L = 30.