2. Sound is a form of energy
• Sound is a form of energy that makes us hear.
• List out the sounds that you hear
• At home
• At school
• At music concert
• At factories
• Human voice
7. Human voice- every person has unique voice
Lata Mangeshkar
A. R. Rehman
Mohamad Rafi
8. Observation about sound
• Each sound is special to the object which produces it.
• Eg. Ticking of clock
• Click of electric switch
• Whirr- sound of rotation of fan
• Buzzing of bees
• Buzzing of mosquitos
• Rustling of leaves
• Every sound has unique ‘quality’ which distinguishes it from other sounds
• Sound helps to communicate to each other
9. Sound is produced by vibrating objects
By vibrating string:
Take a rubber band. Put it around the longer side of a pencil box. Insert two
pencils between the box and the stretched rubber. Now, pluck the rubber
band somewhere in the middle. You will hear sound and the band vibrates.
The to and fro or back and forth motion of an object is termed as vibration.
When a tightly stretched band is plucked, it vibrates and produces sound.
When it stops vibrating, it does not produce any sound.
10. Take a hollow coconut shell and make a musical
instrument Ektara. You can also make it with the
help of an earthen pot. Play this instrument and
identify its vibrating part.
11. A sitar belongs to the musical instrument family call LUTE. Lute family has all
the plucked string instruments (Plucking is a way of pulling and releasing the
string in a particular way to make it vibrate or to stop at a particular pitch. This
can be done with either a plectrum or a finger.) The instruments in this family
are sitar, bass guitar, banjo, mandolin etc).This instrument is mostly used in
Hindustani classical music ( There are two forms of classical Music : Hindustani
and Carnatic).
Guitar
Veena
12. Vibrating Air column
The air inside the pipes of a wind instrument vibrates. The
result is longitudinal standing waves in the air column inside
the pipe. The ends, whether open or closed, create nodes or
antinodes in these standing waves. On a string, the reason for
nodes at the ends of standing wave on a string is obvious.
13. By vibrating plates
Try it out:
Ring a bicycle bell and cover it by putting your palm on it,
the vibrations stop immediately.
Why do you think this happens?
Cymbals in an orchestra
14. Vibration of stretched membrane
Membrane musical instruments
A thin membrane fixed tightly over a hollow wooden drum vibrates and produces sound. We have to
strike the stretched membrane of the instrument with our hands or with sticks to make it vibrate and
produce sound.
For example: Mridangam, tabla , Dholak ,drums ,Dhapli.
15. • The human being produce the sound by using the voice box called
‘larynx’.
• It is situated in our throat at the top of the wind pipe(trachea).
• The voice box contains two ligaments known as vocal cords.
Sound is produced when our vocal cords
vibrate
16. • When we are not talking, the muscles of vocal cord are relaxed due to
which the vocal cords are separated and loose. The air from the lung
passes through them without producing a sound.
• When we talk the muscles of vocal cords contract and stretch, the vocal
cord become tight and thin. The air passes through this narrow slit
between them which will make vocal cord vibrate. These vibrating vocal
cords produces sound.
• The vocal cords of a man are 20mm long
• The vocal cord of women are 15mm long
• Due to the shorter vocal cords the frequency (pitch)of woman’s voice is
more than that of man.
• Small children have very short vocal cord due to which the frequency of
their voice is very high.
17. Activity to demonstrate the working of the
vocal cords
1. Take two rubber strips of same size.
2. Hold the two ends of the rubber strips in your hand and
stretch them tight.
3. Keep the stretched rubber strip in front of your mouth
and blow air through the thin gap between them.
4. When the air rushes through the thin gap, rubber strips
starts vibrating and produces the sound.
5. Vocal cord produce sound in a similar way.
18. Conclusion:
Sound can be produced by following method
• By vibrating string
• By vibrating air column
• By vibrating membrane
• By vibrating plates
19.
20. Q & A
• How is sound produced?
• What should an object do to produce sound?
• How does the sound making objects differs from the one that is
silent?
• What is the length of the vocal cord in a man?
• Out of man and woman who has shorter vocal cords
And who produces sound of higher pitch ?
Name the part which vibrates to produce sound in the
a) Drum b) Sitar c) Flute
