2. Dolphins and other ocean-dwelling animals rely upon
sound waves to communicate with other animals and to
locate food and obstacles. The reason that they are able to
effectively use this method od communication is that
sound travels so much faster in water.
3. SPEED OF SOUND AND DENSITY
SOUND WAVES can travel through other materials besides air.
Speed of sound in a given medium depends on the density of the medium.
Sound is fastest in solid (because the molecules within are closed together), and
slowest in gases (because molecules within are far from each other.
For instance:
During the Japanese era, soldiers lie flat with their ears on the ground to listen
the footsteps of approaching enemies. (steps can be heard even from a distance)
Laying your head on top of the table while someone else taps it.
4. Medium
Speed of sound
(m/s)
Medium
Speed of sound
(m/s)
GASES SOLID
Carbon dioxide 260 Rubber 60
Air (20oC) 343 Lead 1322
Helium (0oC) 972 Concrete 3100
Hydrogen (0oC) 1290 Copper 3560
Oxygen (0oC 317 Iron 5000
LIQUID Aluminum 5100
Water (25oC) 1490 Pyrex 5640
Seawater (25oC) 1530 Steel 5790
5. SPEED AND ELASTICITY
ELASTICITY OF MATERIAL also affects the speed of the sound.
It refers to its tendency to maintain its shape and not deform when a force applied to it.
Rigid materials such as steel experiences smaller deformation when a force is
applied because rubber is more flexible.
Elastic materials vibrate at lower speeds (particles retun to its original position at
lower rates)
Sound travels very slowly in elastic materials than rigid materials.
Reason why rubber is best used as soundproofing.
Elastic properties of material have greater influence on the speed of sound than
density.
6. SPEED AND TEMPERATURE
Sounds travel faster in higher temperature.
If substance heats up, the molecules move faster, collision is more frequent.
More frequent the collisions, the faster the speed of sound in the material.
The speed of sound in an ideal gas v, for example, in a given temperature T in Kelvin
is given by:
v = v0
𝑻
𝑻 𝟎
Where v0 is the speed of sound at absolute temperature T0.
7. Speed of sound in air can be approximated using the equation:
V = 331 m/s + (0.606
𝒎/𝒔
𝒐 𝑪
) Tc
where Tc is the temperature of the air in oC.
