Page 91 - Genius Kidz Prudence Learning Sc-8

Stapes
out, water particles vibrate around us and (attached to
these particles produce sound. Speed of oval window) Semicircular
Canals
sound in water is about 1450 m/sec. Malleus Incus Vestibular
Nerve

Cochlear
Nerve
Cochlea
External
Auditory Canal Tympanic
Cavity
Tympanic Eustachian Tube
Membrane Round
Window

Diagram of an ear

Respiration in water (ii) Middle ear : It is also called as ear drum.
(c) Sound propagation through solids : Sound Sound generates vibrations in the ear
movement is maximum in the case of solids drum.
because of close vicinity of the particles. (iii) Inner ear : Vibrations of the ear drum are
For example, I think each of us must have transmitted on to the hair like projections
experienced that when we put our head on of nerve cells of inner ear.
the table we hear the sound in it. It is
Nerve cell vibrations generate electrical
nothing but the vibrating particles of the
signals perceived by brain that, in turn,
solid that generate sound. generate sound.

(d) Sound propagation through vacuum : SOUND LOUDNESS
Vacuum is the space or region without
Heavier sound is the louder one.
medium or air. Sound doesn't propagate

through vacuum. If there is vacuum Loudness = (Amplitude of vibration) 2
between source of sound and sound That means, larger the amplitude, heavier the
detector then sound does not travel in it or sound will be.
it cannot be heard. Smaller the amplitude, softer and gentle the
How we hear : Ear can detect the sound sound will be. Loudness is proportional to the

produced by any source that is within the square of the amplitude. This mean that if the
audible frequency range (i.e. the frequency amplitude is doubled, the loudness increases
that we can hear). Though we can hear sound by four times.
in the range of 20-20,000 Hz we can produce Heavier sound can be heard over longer
sound with in a range of only 60 - 13,000 Hz. distance.

The parts of human ear are the following. NOISE
(i) Outer ear : It is of conical shape. It consists Any unwanted on unpleasing sound is termed
of ear canal that can transmit the incoming as noise. The noise if too loud can even cause
sound to the ear drum or middle ear.

On one square inch of human skin there are 20 million microscopic creatures.

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