Speed of Sound

Speed of sound

Introduction to Speed of sound

What is the speed of sound in air?

What do you mean by speed of sound?

Sound waves are a series of oscillations of air particles
(compressions & rarefactions). Speed refers to how fast the
oscillations are transferred from one particle to another.

Introduction to Speed of sound

Concorde

Racing car

Speed of sound in air is 330 m/s, which is slower than
Concorde but about four times faster than a racing car.

What do you mean by speed of sound?

Sound is slow

Why thunder is heard after we see lightning?

Sound is much slower than light. Speed of
sound is 330 m/s and speed of light is 3 x 108
m/s. This means, in 3 seconds sound can
travel 1 km approximately but in 1 second
light can travel 3 x 105 km (300,000 km)!
So, we hear lightning after we see it.

Characteristics of Speed of sound

warmer air- faster sound

colder air- slower sound

So, what basic idea we get from this?

Characteristics of Speed of sound

warmer air- faster sound

colder air- slower sound

Speed of sound
depends on the
temperature of
the air.

1. Speed of
sound depends
on the
temperature of
the air.
(hot air-faster
cold air- slower).

Characteristics of Speed of sound

2. The speed of
sound does not
depend on the
pressure of the
air.

Speed of sound is not altered by the
variations in different levels of
atmosphere.

Characteristics of Speed of sound

Sound waves can
travel through walls,
windows, doors,
ceilings, etc.,

Sound waves can
travel through
liquids. We can hear
when swimming
underwater.

Most sound waves
reaching our ear
have travelled
through air.

Solid
liquid
gas

Characteristics of Speed of sound

3. The speed of
sound is different
through different
materials.

1. Speed of
sound depends
on the
temperature of
the air.
(hot air-faster
cold air- slower).

2. The speed of
sound does not
depend on the
pressure of the
air.

Measuring the Speed of sound

The speed of sound can be measured as shown below.

Sound is made by
hitting a metal block
with a hammer.

When the control unit receives a
pulse of sound from microphone A,
it starts the clock.

When it receives a
pulse of sound from
microphone B, it
stops the clock.

Measuring the Speed of sound

If B is 1.00 metre away from the source of
sound than A, and the clock records a time of
3.0 milliseconds (0.003 s):
speed of sound = distance travelled/ time taken
= 1.00 m
0.003 s
330 m/s

Echoes

Echoes are reflection of sound waves. Hard surfaces such as walls
reflect sound waves. We can hear an echo short time after the
original sound.

Sound has to travel to the wall and back
again. The time it takes is the echo
time.

speed of sound = distance travelled
time taken
= 2 x distance to wall
echo time

Applications of sound reflection (echoes)

If the speed of sound is known, and the echo time is measured
accurately, the distance to the wall can be calculated. This
principle is used in several devices. Examples:

A surveyor can use this to measure the
distance between two walls. It works like
an echo-sounder.

This measures the depth of water under a
boat. It sends pulses of sound waves
towards the sea-bed and measures the
echo time. The longer the time, the
deeper the water.

Multiple Choice

Sound does not travel in space because

• Space is too far away.
• There is no matter in space.
• Space is the final frontier
• Space has planets.

Multiple Choice

Sound moves in a _________.

• Transverse wave
• Longitudinal wave

Multiple Choice

Which state of matter do sounds travel fastest in?

• Solid

• Liquid

• Gas

• Plasma

Multiple Choice

Why does sound travel faster in solids than in liquids or gases.

• They are harder.

• The particles are closer together.

• Solids have more energy.

• Gases fill their container.

Multiple Choice

Why does sound travel faster in solids than in liquids or gases.

• They are harder.

• Solids are more dense.

• Solids have more energy.

• Gases fill their container.

Multiple Choice

Roughly what is the speed of sound in air?

• The speed of light.

• About 10 m/s

• About 340 m/s

• About 1 500 m/s

Multiple Choice

Roughly what is the speed of sound in water?

• About 350 m/s

• About 1 500 m/s

• About 5000 m/s

• About 1800 m/s

Multiple Choice

Roughly what is the speed of sound in steel?

• About 350 m/s

• About 1 500 m/s

• About 5000 m/s

• About 1800 m/s

Multiple Choice

Roughly what is the speed of sound in rubber?

• About 50 m/s

• About 1 500 m/s

• About 5000 m/s

• About 1800 m/s

Multiple Choice

Calculate the speed of sound if a sound wave travels 680 m in 2 seconds.

• 1360 m/s

• 340 m/s

• The speed of sound is always the same

• 250 m/s

Multiple Choice

A sound wave travels through water at a speed of 1500m/s for 3.0 seconds. What distance does it travel?

• 750m

• 4 500m

• 428.57m

• 365m

Multiple Choice

Which state of matter do sounds travel fastest in?

• Solid

• Liquid

• Gas

• Plasma

Multiple Choice

Why does sound travel faster in solids than in liquids or gases.

• They are harder.

• The particles are closer together.

• Solids have more energy.

• Gases fill their container.

Multiple Choice

Why does sound travel faster in solids than in liquids or gases.

• They are harder.

• Solids are more dense.

• Solids have more energy.

• Gases fill their container.

Multiple Choice

Calculate the speed of sound if a sound wave travels 680 m in 2 seconds.

• 1360 m/s

• 340 m/s

• The speed of sound is always the same

• 250 m/s

Multiple Choice

Calculate the speed of sound if a sound wave travels 1020 m in 3 seconds.

• 3060

• 365 m/s

• 340 m/s

• 250 m/s

Multiple Choice

A sound wave travels through water at a speed of 1500m/s for 2 seconds. How far does it travel?

• 750m

• 340m

• 3000m

• 300 000 000 m/s

Multiple Choice

A sound wave travels through water at a speed of 1500m/s for 3.5 seconds. What distance does it travel?

• 750m

• 4 500m

• 428.57m

• 365m

Multiple Choice

A sound wave travels through air. It travels 3 400m at a speed of 340 m/s. How long does it take to get there?

• 102000 seconds

• 666 seconds

• 4.25 seconds

• 10 seconds

Multiple Choice

A sound wave travels through air. It travels 1 700m at a speed of 340 m/s. How long does it take to get there?

• 578 000 seconds

• 666 seconds

• 4.25 seconds

• 5 seconds

Multiple Choice

The speed of sound at 20 degrees celcius is:

• 331 m/s
• 365 m/s
• 621 m/s
• 343 m/s

Multiple Choice

A teacher tries to work out the speed of sound. She bangs two bits of wood together. She hears an echo from a wall. The wall is 25m away. How far has the sound travelled?

• 340 m

• 25 m

• 50 m

• 12.5 m

Multiple Choice

A teacher bangs two bits of wood together. She hears an echo from a wall 0.14 seconds later. The wall is 25m away. What is the rough speed of sound, ACCORDING TO THESE RESULTS?

• Roughly 340 m/s

• Roughly 360 m/s

• Roughly 375 m/s

• Roughly 330 m/s