Speed of sound:

Speed of sound:

Speed of sound is different in different mediums. In a medium, the speed of sound basically depends upon elasticity and density of medium.

Speed of sound is maximum in solids and minimum in gases.

When sound enters from one medium to another medium, its speed and wavelength changes but frequency remains unchanged.

In a medium, the speed of sound is independent of frequency.

Effect of pressure on speed of sound: The speed of sound is independent of pressure i.e. speed remains unchanged by the increase or decrease of pressure.

Speed of sound in different mediums 

Medium	Speed of sound (In  m/s)
Carbondioxide	260
Air (0˚C)	332
Air (20˚C)	343
Steam (at 100˚C)	405
Helium	965
Alcohal	1213
Hydrogen	1269
Mercury	1450
Water (20˚C)	1482
Sea water	1533
Copper	3560
Iron	5130
Glass	5640
Granite	6000
Aluminum	6420

Effect of temperature on speed of sound:

the speed of sound increases with the increase of temperature of the medium. The speed of sound in air increases by 0.61 m/s when the temperature is increased by 1˚C.

Effect of humidity on speed of sound: The speed of sound is more in humid air than in dry air because the density of humid air is less than the density of dry air.

Characteristics of sound waves: Sound waves have the following three characteristics:

       Intensity: Intensity of sound at any point space is defined as amount of energy passing normally per unit area held around that point per unit time. SI Unit of Intensity is watt/ m².

Intensity of sound at a point is,

(i)                  Inversely proportional to the square of the distance of point from the source.

(ii)                Directly proportional to square of amplitude of vibration, square of frequency and density of the medium.

Due to intensity, a sound appears loud or faint to the ear. Actually, the sensation of a sound perceived in ear is measured by another term called loudness which depends on intensity of sound and sensitiveness of the ear. Unit of loudness is bel. A practical unit of loudness is decibel (dB) which of equal to 1/ 10^th of bel. Another unit of loudness is phon.

2       Pitch:  Pitch is that characteristic of sound which distinguishes a sharp (or shrill) sound from a grave (dull or flat) sound. Pitch depends upon frequency. Higher the frequency, higher will be pitch and shriller will be the sound. Lower the frequency, lower will be the pitch and grave will be the sound.

3       Quality: Quality is that characteristic of sound which enables us to distinguish between sounds produced by two sources having the same intensity and pitch. The quality depends upon number, frequency and relative intensities of overtones.