Page 140 - Science Class 08

HUMAN VOICE why woman have thinner voices. Children have

Human voice is generated in the sound-box even shorter vocal cords. So, their voices are
located inside the throat across the wind-pipe even shriller.
(larynx) through which we inhale and exhale ANIMAL SOUND
air. This box has two loose flaps called vocal Animals like the dog, cat, cow, etc. too have
cords. The cords lie across the larynx such that vocal cords in their throats, but birds have no
they leave a narrow passage between them for vocal cords. They produce sounds by means of
the breath (air) to pass. special organs that are there in their throats.

These organs are rings made of so car lage.
They help them to produce their various cries.
These rings are called syrinx.

Some birds have their voice boxes divided into
two parts. So, they can prooduce two notes at a
me. Bees create a buzzing sound by means of
their fast moving wings. Frogs have vocal cords
that enable them to croak. But, they can inflate
Vocal cords
their throats to amplify their croaks to make
them long and coarse. A snake uses its breath
When the lungs exhale the breath, it passes to create a hissing noise.

through the narrow passage between the vocal
cords and they vibrate to produce a sound.
When these cords are taut and thin, the sound
produced by them is of high frequency. But,
when they are loose and thick, the sound has a
low frequency.

The vocal cords are about 20 mm long in every
male and 15 mm long in every female. That is

Compression : Narrowing down of the sound-carrying layer of the air
Rarefaction : Relaxing of the sound-carrying compressed layer of the air
Obstacle : Any hurdle that comes in the way of travelling sound-waves

Sound-wave : The set of one compression and one rarefaction of sound-carrying vibrations
Reflection : Change in the direction of sound-waves after hitting at an obstacle

Let's R
Let's R
Let's Revise evise Let's Revise evise evise Let's Revise evise
Let's R
Let's R
i Sound travels through compressed and relaxed layers of the air.
i Sound-waves enter the ear and cause the ear-drum to vibrate.

140 Science-8