Speed of Sound (Velocity of Sound)

The velocity of sound refers to the speed at which sound waves travel through a medium, such as air, water, or solids. Sound is a form of energy that moves as vibrations, causing particles in the medium to compress and expand in a wave-like motion. The velocity of sound depends on factors like the medium's density, elasticity, and temperature.

• Sound travels faster in solids (e.g., iron) because particles are tightly packed and can transfer vibrations more efficiently.
• It travels slower in liquids and even slower in gases (e.g., air) due to the greater spacing between particles.

The velocity of sound can be explained using the following principles:

• The distance covered by a point on the wave (e.g., the point of highest or lowest density) in a unit of time is the velocity of the sound wave.
• In one time period (T), any point on the wave covers a distance equal to the wavelength (λ).

The velocity of sound is given by the formula:

Velocity=`"Distance"/"Time"`​

Substituting λ (wavelength) as the distance and $T$ (time period) as the time:

v=`"λ"/"T"`​

Since the reciprocal of the time period is the frequency (ν):

Frequency=`"1"/"T"`​

The velocity of sound can also be expressed as:

v=λν

where:

• $v$: Velocity of sound
• λ: Wavelength (distance between successive compressions or rarefactions)
• ν: Frequency (number of waves passing a point per second)

1. Find a long iron pipe, like those on a staircase or fence.

2. Stand at one end while your friend stands 20–25 feet away at the other end.

3. Ask your friend to tap the pipe with a stone. Listen carefully with your ear pressed against the pipe.

4. You hear two sounds:

• One through the pipe.
• Another through the air.

5. The sound through the pipe reaches you first.

6. Sound travels faster in solids (like iron) than in air. This is because particles in solids are packed closer together, making it easier for vibrations to move.

7. The speed of sound depends on the distance it travels in a certain time.  v = λν