Page 141 - Science Class 08

i The ear-drum sends its vibrations to the three interlocked tubes inside the middle ear.
i These tubes tend the vibrations to the inner ear through the oval window.

i The inner ear’s coiled tube amplifles the sound and sends it to cochlea that balances it.
i From the cochlea, the auditory nerves carry the sound to the brain.
i The brain identifies the sound and the person hears as well as understand it.

i Reflection of sound means its striking at an obstacle and then changing its direction.
i The reflected sound, if heard separately just after the original sound, is called an echo.
i Echoes help in calculating the ocean-depths.

i Noise is an unpleasant sound that results from irregular vibrations.
i Musical sounds are pleasant sounds that result from regular vibrations.
i Musical instruments are four types— stringed instruments, wind instruments, percussion
instruments and jerk instruments.

i Human beings and most animals have vocal cords in their throats that help them to make
their respective sounds.
i Birds have no vocal cords, but only cartilage rings.

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A. Tick (3) the correct op on.
1. Sound travels in the form of:
(a) currents (b) waves
(c) sudden leaps (d) air
2. The outer ear extends up to the:
(a) ear-drum (b) hammer

(c) oval window (d) none of these
3. The sound is changed into signals in the:
(a) s rrup (b) cochlea
(c) anvil (d) syrinx

4. The creatures without vocal cords are:
(a) rep les (b) birds
(c) insects (d) humans
B. Match the following columns.

Column I Column II
1. Coiled tube a. Sound-waves strike at it
2. Brain b. Hearer of a sound
3. Source c. Amplifies the sound
4. Detector d. Iden fies the sound
5. Ear-drum e. Origin of a sound

Science-8 141