2. OBJECTIVES:
• Explain the concepts of speed of sound
• Derive the formula for speed of sound
• Determine what are the factors that affects the speed of
sound
• Identify how speed of sound travels in different media
3. What is Sound?
Sound is a vibration or noise that passes through some
medium.
It travels by moving energy from one molecule to the next
and can be quickly heard as it enters a person’s ear.
For example, when an object vibrates, it passes energy to
the surrounding particles, causing them to vibrate as well.
4. What is Sound Wave?
Sound is a wave that travels as longitudinal waves through
air and liquid, but as both longitudinal and transverse waves
through solid. The intensity at which a sound wave
propagates is determined by the properties of the medium in
which it travels. Its speed is independent of the wave’s
characteristics or the force that produces it.
5. WHAT IS SPEED OF SOUND?
• The speed of sound is defined as the distance through
which a sound wave’s point, such as a compression or a
rarefaction, travels per unit of time. The speed of sound
remains the same for all frequencies in a given medium
under the same physical conditions.
• The dynamic propagation of sound waves is known as
the speed of sound.
6. • The term “speed of sound” refers to the velocity of
sound waves in an elastic medium. Hence, the
speed of sound defines how quickly it can propagate in
some medium. The speed depends on
the medium.
7. HOW TO CALCULATE SPEED OF
SOUND?
• Since the speed of sound is the distance travelled by the
sound wave in a given time, the speed of sound can be
determined by the following formula:
v = λ f
• Where v is the velocity, λ is the wavelength of the sound wave, and f is
the frequency.
• The relationship of the speed of sound, its frequency, and wavelength is
the same as for all waves. The wavelength of a sound is the distance
between adjacent compressions or rarefactions. The frequency is the
same as the source’s and is the number of waves that pass a point per
unit time.
8. FOR EXAMPLE:
Solved Example:
• How long does it take for a sound wave of frequency 2 kHz and
a wavelength of 35 cm to travel a distance of 1.5 km?
Solution:
We know that the speed of sound is given by the formula:
v = λ ν
Substituting the values in the equation, we get
v = 0.35 m × 2000 Hz = 700 m/s
The time taken by the sound wave to travel a distance of 1.5 km can
be calculated as follows:
Time = Distance Travelled/ Velocity
Substituting the values in the equation, we get
Time = 1500 m/ 700 m/s = 2.1 s
9. FACTORS THAT CAN AFFECT THE
SPEED OF SOUND
Density of the Medium
• When the medium is dense, the molecules in the
medium are closely packed, which means that the sound
travels faster. Therefore, the speed of sound increases
as the density of the medium increases.
Temperature of the Medium
• The speed of sound is directly proportional to the
temperature. Therefore, as the temperature increases,
the speed of sound increases.
10. SPEED OF SOUND IN AIR
• The speed of sound is an important parameter in many
fields of physics. The distance traveled per unit time by a
sound wave propagating through a medium is referred to
as the speed of sound.
• At 20 °C, the speed of sound in air is 343.2 m/s, which
corresponds to 1,236 km/h. At this rate sound will travel
one mile in around five seconds. Sound travels 4 times
faster in water (1,482 meters per second) and around 13
times faster through steel (4,512 meters per second).
11. SPEED OF SOUND IN
DIFFERENT MEDIA
• The speed of sound depends on the properties of the medium
through which it travels. The speed of sound decreases when
we go from a solid to a gaseous state. In any medium, as we
increase the temperature, the speed of sound increases.
• Since sound needs a medium for its propagation, it can travel
through different media like;
- Solid
- Liquid
- Gas
12. SPEED OF SOUND IN SOLID
• Solids are significantly denser than liquids or gases, and
this means that the molecules are closer to each other in
solids than in liquids and liquids than in gases. This
closeness due to density means that they can collide
very quickly. Effectively it takes less time for a molecule
of a solid to bump into its neighboring molecule. Due to
this advantage, the speed of sound in a solid is faster
than in a gas.
13. • The speed of sound in solid is 6000 meters per second,
while the speed of sound in steel is equal to 5100 meters
per second. Another interesting fact about the speed of
sound is that sound travels 35 times faster in diamonds
than in the air.
14. SPEED OF SOUND IN LIQUID
• A liquid’s density is higher than a gas’s density. As a
result, the distances between molecules in liquids are
greater than in solids but smaller than in gases. As a
result, the speed of sound in liquids is intermediate
between the speeds of sound in solids and gases.
15. Speed of Sound in Water:
The speed of sound in water exceeds that of air.
Alternatively, sound moves quicker in water than in air. In
water, the speed of sound is 1480 m/s. It’s also worth
noting that the speed of purified water will range from
1450 to 1498 m/s, while the speed of seawater ranges
from 1531 m/s while the temperature is between 20 °C
and 25 °C.
16. SPEED OF SOUND IN GAS
• When sound approaches a liquid or solid, the speed of
sound is independent of the density of the medium.
Since gases expand to fill a given vacuum, their density
is very uniform regardless of the type of gas. This is
obviously not the case for solids and liquids.
17. SPEED OF SOUND IN VACUUM
• Since there are no particles in a vacuum, the speed of
sound is zero metres per second. When there are ions
for the propagation of these sound waves, they fly
through a medium. Sound waves do not propagate in the
vacuum since it is an empty space.
18. In general, sound waves fly the fastest
through solids, then liquids, and finally gases. In
gases, the speed of sound is equal to the square
root of the absolute temperature (measured in
Kelvin), but it is unaffected by the frequency of
the sound wave, strain, or density of the medium.
However, none of the gases we encounter in
everyday life are ideal gases, and as a result,
their properties vary slightly.
