Question

i) Explain the factors affecting on the velocity of sound in gaseous medium.
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Answer 1

Answer:

The velocity of sound in a gas is inversely proportional to the square root of the density of the gas. When the humidity of air increases, the amount of water vapour present in it also increases and hence its density decreases, because the density of water vapour is less than that of dry air.

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Explaining

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

Effect of density

Consider two different gases at the same temperature and pressure with different densities. The velocity of sound in two gases are given by

v1 = γ1 P / ρ1 and v2 = γ2 P / ρ2

For gases having same value of γ,

v1 / v2 = root[ρ2/ ρ1 ]

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

Velocity of sound in various media

Medium Velocity (ms1)

Gases Air 0o C 331

Air 20o C 343

Helium 965

Hydrogen 1284

Liquids Water 0o C 1402

Water at 20o C 1482

Sea water 1522

Solids Aluminum 6420

Steel 5921

Granite 6000

Answer 2

Explanation:

EFFECT OF DENSITY ON SPEED OF SOUND - RESULT

v=ργP

v∝ρ1

Hence, speed of sound decreases with increase in the density of the medium.

EFFECT OF TEMPERATURE ON SPEED OF SOUND - RESULT

VT2=VT1+0.61(T2−T1)

where

VT2: speed of sound wave at temperature T2

VT1: speed of sound wave at temperature T1

Hence, speed of sound increases with increase in temperature.

EFFECT OF HUMIDITY ON SPEED OF SOUND - RESULT

Speed of sound increases in proportion to humidity in air. Humidity has a small but significant effect on speed of sound (causing it to increase by about 0.1%-0.6%), the reason being oxygen and nitrogen molecules of the air are replaced by lighter molecules of water.

The approximate speed of sound in dry (0% humidity) air, in meters per second, at temperatures near 00 C, can be calculated from:

 v=(331.3+0.606T) m/s

EFFECT OF DIRECTION OF WIND ON SPEED OF SOUND - RESULT

The speed of sound increases when the sound wave is moving in the direction of wind.

The speed of sound decreases when the sound wave is moving in the direction opposite to the direction of wind