Grade 7 Science Third Quarter Module 3

1. SOUND
Mrs. Solita M. De Leon

2. How does sound propagate?

3. Activity 1
My own sounding box
In this activity, you should be able to construct a
sounding box to
1. demonstrate how sound is produced; and
2. identify factors that affect the pitch and
loudness of the sound produced.

4. Procedure
1.Cut and design your shoe box as shown in the
figure below.

5. 2. Put the rubber bands around the box. Make
sure that the rubber bands are almost equally
spaced and that the rubber bands are
arranged according to increasing thickness
from the lower end to the other end of the
box.
3. Use your finger to pluck each rubber band.
Listen to the sound produced.

6. Q1. What physical signs did you observe when
you plucked each band. Did you hear any
sound? What produced the sound?
Q2. How different are the sounds produced by
each band with different thickness?

7. 4. This time use the fingers of one hand to
stretch one of the elastics. Pluck the
elastic with the fingers of the other hand and
observe.
Q3. Are there changes in the note when you
plucked the stretched band?

8. 5. Repeat step 4 with the other elastic bands.
Q4. Arrange the elastics in sequence from the
highest note to the lowest note produced.

9. Sound
• is a form of energy produced & transmitted
by vibrating matter

10. How is sound produced?
• Sounds are caused by vibrations.
• Vibrations are considered as a disturbance
that travels through a medium.
• This vibratory motion causes energy to
transfer to our ears and is interpreted by our
brain.

11. Vibration
- Very fast, repeated backward and forward
movement of particles of matter
- For example, the vibration of the tuning fork creates pure
sound.
- The hammer hits the nail and the particles vibrate making
noise.

12. Sound . . .
• Sound waves are examples of longitudinal
waves.
• They are also known as mechanical waves
since sound waves need medium in order to
propagate.

13. Waves transport energy without
moving matter
Watch the 3 red dots
You will see them
vibrate, but not move
with the wave to the
end.
All the particles are
vibrating but stay
fixed

14. `
• As air molecules collide with those nearby,
they cause other air molecules to move back
and forth.
• In this way, energy is transferred from one
place to another.

15. The Speed of Sound

16. Sound waves and the
States of Matter

17. The Speed of Sound
• Sound waves can travel through other
materials besides air.
• As a sound wave travels through a material,
the particles in the material collide with each
other.
• In a solid, molecules are closer together than
in liquids or gases, so collisions between
molecules occur more rapidly than in liquids
or gases.

18. Sound also travels faster in liquids than in
gases because molecules are still more tightly
packed. In fresh water, sound waves travel 4
times faster than in air!
Speed of Sound

19. Speed of Sound

20. Factors Affecting Speed of Sound
(1) Atmospheric pressure
(2) relative humidity
(3) atmospheric temperature.
• High atmospheric pressure, relative humidity
and atmospheric temperature lead to faster
moving sound.

21. Why sound travels faster in hot
air?
• The temperature of the material that sound
waves are traveling through also affects the
speed of sound.
• As a substance heats up, its molecules move
faster, so they collide more frequently.
• The more frequent the collisions are, the faster
the speed of sound is in the material.

22. Check Your Understanding
1. Which of the following objects will produce
sound?
a. soft objects
b. radio stations
c. vibrating objects
d. objects under pressure

23. Check Your Understanding
2. A sound wave is a _____________.
a. longitudinal wave
b. transverse wave
c. standing wave
d. shock wave

24. Check Your Understanding
3. Which of the following is not capable of
transmitting sound?
a. air
b. water
c. steel
d. a vacuum

25. Check Your Understanding
4. Which of the following would most likely
transmit sound best?
a. Steel in cabinet
b. Water in the ocean
c. Air in your classroom
d. Water in a swimming pool

26. Check Your Understanding
5. In which of the following does sound travel
fastest?
a. gases
b. liquids
c. solids
d. air

27. Sound cannot travel in a vacuum.
• Remember that sound is a mechanical wave
which needs medium in order to propagate.
• If no matter exists, there will be no sound.
• In the outer space, sound would not be
transmitted.

28. Properties and characteristics of
sound

31. Properties and characteristics of
sound
• Strum each guitar string without holding the
frets. (String #0 is the lower most string while
string #6 is the uppermost string.

33. Pitch
• The highness or lowness of sound is known as
the pitch of a sound.

34. 1. Which string vibrates fastest when
strummed?
String #0
2. Which string vibrates slowest when
strummed?
String No. 6
3. Which string has the highest frequency?
String No. 0

35. • Which string has the highest pitch?
String No. 0
• Which has the lowest frequency?
String No. 6
• Which string has the lowest pitch?
String No. 6
• How would you relate pitch and frequency?
The higher the frequency, the higher the
pitch.

36. 1.1. Lengthening of the stringLengthening of the string
– The shorter the length of theThe shorter the length of the
string, the higher the magnitudestring, the higher the magnitude
of the pitch.of the pitch.
1.1. Thickness of stringThickness of string
– As the diameter of a stringAs the diameter of a string
decreases the pitch of the sounddecreases the pitch of the sound
wave increaseswave increases
What are the different factorsWhat are the different factors
affecting the pitch of a sound?affecting the pitch of a sound?

37. How is frequency andHow is frequency and
pitch related?pitch related?
The greater the frequency ofThe greater the frequency of
sound wave, the higher thesound wave, the higher the
pitch of sound wavepitch of sound wave
produced.produced.

38. Characteristics of soundCharacteristics of sound
wave:wave:
1.1. LoudnessLoudness
• Loudness of soundLoudness of sound
largely depends on thelargely depends on the
intensity of sound.intensity of sound.
• The greater theThe greater the
amplitude, the louderamplitude, the louder
the sound producedthe sound produced

39. 2. Pitch and frequency.2. Pitch and frequency.
•Pitch refers to the highnessPitch refers to the highness
or lowness of soundor lowness of sound
•The pitch sound depends onThe pitch sound depends on
the frequencythe frequency
•The greater the frequency,The greater the frequency,
the higher the pitch ofthe higher the pitch of
soundsound

40. 3. Intensity3. Intensity
• The measure of theThe measure of the
energy per unit timeenergy per unit time
transmitted through atransmitted through a
unit area by the soundunit area by the sound
wave.wave.
• Intensity levels areIntensity levels are
expressed in decibelsexpressed in decibels
(dB)(dB)

41. The Human Ear

42. Major Parts of the Ear
1. the outer ear
2. the middle ear and
3. the inner ear

43. Parts of the ear
• The outer ear called the pinna collects
the sound waves and focuses them into
the ear canal.
• This canal transmits the sound waves to
the eardrum.

44. Parts of the ear
• The ear canal is the eardrum membrane
or the tympanum.
• It separates the outer and the middle
ears physically.

45. Parts of the ear
• Air vibrations set the eardrum membrane in
motion that causes the three smallest bones
(hammer, anvil and stirrup) to move.
• These three bones convert the small-
amplitude vibration of the eardrum into large
amplitude oscillations.
• These oscillations are transferred to the inner
ear through the oval window.

46. Parts of the ear
• Behind the oval window is a snail-shell shaped
liquid –filled organ called the cochlea.
• The large-amplitude oscillations create waves
that travel in liquid.
• These sounds are converted into electrical
impulses, which are sent to the brain by the
auditory nerve.
• The brain, interprets these signals as words,
music or noise.

47. • Audio frequency rangeAudio frequency range
- Frequency rangingFrequency ranging 20 Hz to 20 000 Hz20 Hz to 20 000 Hz
- Sounds thatSounds that human earhuman ear can hear is ancan hear is an
example.example.
• INFRASONICSINFRASONICS
• -Frequency below-Frequency below 20 Hz.20 Hz.
• ULTRASONICSULTRASONICS
• -Frequency above 20 000 Hz-Frequency above 20 000 Hz

48. Ultrasonic and Infrasonic
Frequencies
• Vibrational frequencies beyond 20 000
Hz is called ultrasonic frequencies
• extremely low frequencies are known as
infrasonic frequencies.

49. • Our ear cannot detect ultrasonic or
infrasonic waves.
• Some animals like dogs can hear sounds
as high as 50 000 Hz
Ultrasonic and Infrasonic Frequencies

50. Ultrasonic and Infrasonic Frequencies
• Bats can detect sounds as high as
100 000 Hz.

51. Applications of Sound Waves
• We can see images of your baby brother or
sister when the OBGyne asks your mommy or
nanay to undergo ultrasound.

52. Applications of Sound Waves
• It has also been found that ultrasonic waves
can be used as rodent and insect
exterminators.

53. Check Your Understanding
1. Which of the following best describes a high
frequency sound? It has _____________.
a. low pitch
b. high pitch
c. low energy
d. A and C

54. Check Your Understanding
2. Compared to a thin string of the same length
and tightness a thick string produces sounds
of ____________.
a. the same pitch
b. lower pitch
c. higher pitch
d. lower then higher pitch

55. Check Your Understanding
3. The unit for sound intensity is the
a. Deciibel
b. Seconds
c. Hertz
d. meters

56. Check Your Understanding
4. The part of the ear where sound is converted
to electrical energy and sent to the brain
a. Tympanum
b. Ear canal
c. Cochlea
d. anvil

57. Check Your Understanding
5. Which of the following frequencies can be
heard by the human ear?
a. 35,000 Hz
b. 30,000 Hz
c. 18,000 Hz
d. 45,000 Hz

58. The End