**Sound Intensity Formula**

Sound intensity is defined as sound per unit area perpendicular to direction of sound waves represented by I. The SI unit of sound intensity is watt per square meter (W/m2). The standard text is the measurement of sound intensity of the noise in the air at the location of the listener as a sound energy quantity.

The sound intensity formula is given as,

Where,

**P **= sound power,

**A **= area

To measure Sound intensity level, you need to compare the given sound intensity with the standard intensity.

**Sound Intensity Level** **Formula** is given as,

Where **I** = sound intensity and

**I****o** = reference intensity

It is expressed in decibels **(dB)**.

**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:

Sound power P = 0.9 × 10-4 W,

Area A = 7m

Sound intensity formula is given by I = P / A

= 0.9×10−4 / 7

= 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,

Io = 10-12 Wm-2

IL= 10 log10 1×10−9 / 10−12

= 10 log10 103

= 3.