Sound Energy

INTEGRATED SCIENCE
WEEK 3:

By:

BY MR. AHENKAN YEBOAH

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GHANA CHRISTIAN INT. HIGH SCHOOL

TOPIC: SOUND ENERGY
SUBTOPIC: SOUND ENERGY

By the end of this lesson learners must be able to:

explain the sources and nature of sound.

describe musical notes and distinguish musical notes from noise.

dentify the parts of the human ear and describe
their functions.

SOUND ENERGY

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SOUND ENERGY

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Sound energy is a form of energy that is associated with
vibration of matter.
Although sound is a form of energy, it is not measured
in joule like the other forms of energy.
This is because the amount of energy in a sound wave is
far smaller and cannot be transformed into other
energy forms.
Sound intensity is instead measured in decibels (dB).

HOW SOUND IS PRODUCED

Sound is produced when

materials vibrates.

Sound waves are created

by the movement of
particles in a medium

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The sources of sound are
categorized based on the mode of
production of a particular sound.
Hence the sources of sound are
categorized as:
1. stringed instruments
2. percussion instruments
3. wind instruments

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Percussion instruments
These are instruments
which produce sound as a
result of the vibration of
the skin or surface when
struck. Examples are
drums, xylophone, gong,
bell etc.

STRINGED INSTRUMENT

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WIND INSTRUMENT

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These are instruments which
vibrate the air around them

to produce sound.

Examples are flute, trumpet,
organ, accordion etc.

sosou

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1. MECHANICAL WAVE
Mechanical waves are
waves which need
material medium for
their transmission.

2. ELECTROMAGNETIC WAVE

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Mechanical waves

They are in two types –

• Transverse waves and

• Longitudinal waves (sound travel as longituninal

wave).

In both cases, only the energy of wave motion is
propagated through the medium; no portion of
the medium itself actually moves very far.

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Similarities between electromagnetic
waves and mechanical waves

1. They can both be polarised.

2. Both can be interfered and diffracted.

3. Both can be reflected and refracted.

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Terms Associated with Sound Waves

Frequency
Amplitude
Wavelength

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OR

Frequency is the number of cycles or
oscillations a sound wave makes per
second.

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Amplitude

Amplitude is the maximum displacement of vibrating or
distorted particle from it mean or equilibrium position.

ü It is the characteristic of sound waves that humans perceive

as volume.

ü The amplitude corresponds to the distance that air molecules

move back and forth as a sound wave passes through them.

ü As the amount of motion in the molecules is increased, they

strike the ear drum with progressively greater force.

This causes the ear to perceive a louder sound.

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Wavelength

It can also be defined as the distance
between any two refractions or
compressions.
The distance at which a sound can be
heard depends on its wavelength.
The wavelength of sound is the
average rate of flow of energy per
unit area perpendicular to the
direction of propagation.
Wavelength is measured in metre
(m).

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Velocity of a sound wave is the

product of frequency and
wavelength.

This is expressed

mathematically as:

velocity = frequency x wavelength
Or v = fג

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Speed of sound in gases

The speed of sound in dry, sea level air
at a temperature of 0 °C is 332 m/s.
The speed of sound in air varies under
different conditions.
If the temperature is increased,
for example, the speed of sound
increases; thus, at 20 °C, the speed of
sound is 344 m/s.
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Factors affecting the
velocity of sound in a gas
medium

1. Nature of the gas
2. The presence of gas
3. the temperature of the
gas

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Comparison of velocity of light and sound

Sound waves travel
slower than light, this
is the reason why if
you watch an action at
a distance, you see
that action before
hearing the
accompanying sound.

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INTEGRATED SCIENCE
WEEK 3:

By:

BY MR. AHENKAN YEBOAH

GHANA CHRISTIAN INT. HIGH SCHOOL

TOPIC: SOUND ENERGY
SUBTOPIC: SOUND ENERGY

By the end of this lesson learners must be able to:

describe musical notes and distinguish musical notes from noise.

dentify the parts of the human ear and describe
their functions.

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Factors affecting
loudness of sound
1. Amplitude
2. Energy of

vibration or
magnitude of
sound wave

3. Volume of air

vibrating

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The quality of a musical
note that distinguishes one
musical note from others of
the same pitch or loudness.
It is referred to as the colour
or texture of the note.

3. Quality or Timbre

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Reflection of sound waves

This is the
bouncing
back of a
sound wave
when it hits a
hard surface.

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Uses of echo

1. An echo can be used to estimate the distance
of an object, its size, shape and velocity, as well
as the velocity of sound itself.
2. It is used to determine the depth of sea bed.
3. It helps in oil and gas exploration.
4. Echoes are used to estimate the thickness of
polar icecap.

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The Doppler Effect

Doppler Effect is the apparent variation in frequency of any
emitted wave as the source of the wave approaches or moves away,
relative to an observer.

Ø Doppler Effect explains why, if a source of sound of a constant

pitch is moving towards an observer, the sound seems higher in
pitch, whereas if the source is moving away it seems lower.

Ø This change in pitch can be heard by an observer listening to

the whistle of an express train from a station platform or
another train.
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Applications of Doppler Effect

1. It is used in radar speed detector used by traffic police for
checking speed.
2. It is used to calculate the relative motion of the earth and
stars.
3. It is used to determine approaching or receding sounds.
4. It is used in weather forecasting
5. It helps bats find their way around when flying in the dark.

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