A sound is a form of energy which gives a sensation of hearing. The sound is produced due to the vibration of the body. Sound travels through a medium by means of waves set up in the medium. The following are the characteristics of sound;

• It is produced due to the vibration of the body.
• It needs a medium for propagation. It cannot travel through a vacuum.
• Its speed is different in a different medium. Its velocity is the highest in solids and slowest in gases.
• Sound travels from one place to another in the form of a longitudinal wave.
• Sound follow reflection and refraction phenomenon.

Relation between frequency and time period

By the definition of frequency,

∴ f vibrates are completed in one second.

∴ 1 vibration is completed in 1/f second.

But, time to complete one vibration is its time period (T)

∴ T = 1/f

Factors affecting velocity of sound in gases

Temperature: The velocity of sound is directly proportional to square root of the absolute temperature of the gas. Thus, higher the temperature, higher the velocity of sound.

∴ Velocity of sound ∝

Density: The velocity of sound in a gas is inversely proportional to the square root of the density of the gas.

∴ Velocity of sound ∝

Humidity: As the density of water vapour is less than that of dry air, the density of moist air is lesser than that of dry air. Sound travels faster in moist air than in dry air as the velocity of sound in a gas is inversely varies inversely to square root of the density of the gas.

The direction of wind: Direction of wind also affect the velocity of sound. The velocity of sound is higher in the direction of wind and slower in the opposite direction of the wind.