FORM 2 CHAPTER 10 SOUND WAVES

10.1 Characteristics of Sound Waves

1. Sound is a form of energy caused by vibration.
2. Sound produced by vibration objects.
3. The air particles surrounding the object vibrate when the

object vibrates.
4. This vibration causes the particles around it to vibrate and

produces a movement pattern as in diagram 10.1 and this is
known as sound waves.

CHAPTER 10: SOUND WAVES
1. Characteristics of sound waves:

a) cannot travels through vacuum
b) can be reflected
c) can be absorbed
d) can travels through solid, liquid and gases.

Sound requires a medium to propagate

Discussion
At first, the sound of the alarm is heard.
• The sound of alarm decreases as the air is removed

from the jar and no sound is heard when all the air
has been removed.

Answer:

Faiq. This is because Faiq’s string taut while Naqib’s
string slack. Slack string cannot transfer sound wave.



Transfer of sound

1. Wood and metal have hard and smooth surfaces that can reflect sound
better.

2. The towel has a soft and rough surfaces that can absorb sound better.

The Reflection of Sound

Hard,and smooth surfaces are good
sound reflectors.
Examples: mirror, marble tiles, and concrete
wall.

The absorption of Sound

Soft and Rough surfaces are good sound
absorbers.

Examples: the carpet, sponge, polystyrene, and
rubber, curtain.

Sound can be reflected and absorbed

Materials Observation
Wooden plank
The sound of the ticking of the clock can be
Metal sheet heard clearly.

towel The sound of the ticking of the clock can be
heard clearer

The sound of the ticking of the clock can be
heard softer.

10.2 Loudness and pitch of sound

Frequency and Amplitude of Sound

1. Sound varies in loudness and pitch.

2. Loudness of a sound depends on its amplitude.
The higher the amplitude of the sound waves, the
louder the sound can be heard.

10.2 Loudness and pitch of sound

Loudness Depends on Unit
Pitch amplitude meter, m

frequency hertz, hz

Amplitude Frequency

Meaning the maximum the complete
distance from the number of waves
equilibrium point. produced within a
second.

Loudness and pitch of sound

1.Loudness of sound is the strength of sound.
2.Its depends on amplitude, the larger the
amplitude, the stronger the loudness of sound.

3. Amplitude, A is the maximum distance from the equilibrium
point. Amplitude is measured in meter or centimeter unit.

4. Pitch of the sound depends on the frequency of the waves.
The higher the frequency of the sound waves, the higher the
pitch.

5. Frequency, f is the complete number of waves produced
within a second. Frequency is measured in Hertz, Hz unit.



6. Musical instruments that can produce notes with a
wide frequency range and pitch:

a) piano
b) guitar
c) violin
d) drum

The changes in frequency can be changed by
altering:

The thickness of the The thicker the string, the lower

string the pitch of the sound produced.

The tension of the The tension the string, the greater
string the pitch of the sound produced.

The length of the The shorter the string, the higher
string the pitch of the sound produced.



Doppler effect

1. The Doppler effect is the change in frequency
caused by the movement of the source of sound, the
observer, or both.
2. As the ambulance approaches the observer:

a) the frequency of the siren increases,
b) the pitch increases.
3. As the ambulance moves away the observer:
a) the frequency of the siren decreases,
b) the pitch decreases.

10.3 Phenomenon and application of reflection
of sound waves

• The echoes is the result of sound waves being
reflected back when they hit a hard surface.

• It often happens inside closed areas like enclosed hall,
an empty room, a cave and a tunnel.

3.Echoes can be used to determine the distance of a
depth and detect the location of an object.

4.Animal like the bat and the dolphin use ultrasound
to detect victims and estimate the distance.

5. The shipping and fishing industry use ultrasound
reflection to detect the depth of the sea and the
location of the fish.

Limitation of hearing

• A normal person hearing range is around 20 to
20 000 Hz (hertz).
• There is also a limit as to how far our ear is able to

hear sound from a distance.
• We also cannot hear very soft sound like our

heartbeats

• ULTRASOUND – A sound wave with a frequency
which is higher than the limit of hearing in human.
( more than 20 000Hz)

• INFRASOUND, - A sound waves with a frequency
below the lower limit of audibility (less than 20 Hz).

• Special devices (alat) are invented to help the
limitation of hearing :







• Old people cannot hear well ,
because as we aged, the eardrum
becomes less elastic and less
sensitive to sound waves.