2. PRODUCTIONOF SOUNDWAVES
Sound is a form of energy
which travels in the form of waves.
It produces hearing sensation in our ears. To
produce sound we are to make vibrations in a
body.
For example: Place a bowl upper side
down and strike it with spoon. The bowl start
vibrating produces particular sound that can
be heard.
3.
4.
5.
6. When prongs of tuning fork are made to
strike with a rubber pad then these begin to
vibrate and sound waves are produced which
spread all around.
Sound waves need a material medium
such as solids, liquids and gases for their
propagation. Most sound waves reaching our
ear have travelled through air. Sound can not
travel through a vacuum.
8. The vibrating body produces sound
waves. These waves are “longitudinal”
waves in nature. The molecules of medium
vibrate, due to sound waves along the
direction of propagation of sound waves.
These are also called compressional
waves.
Propagation of sound waves produced by
vibrating tuning fork.
9. When the right prong of tuning fork
moves from mean position ‘O’ to ‘B’ it exerts
some pressure on the adjacent layer of air
molecules and produces a compression.
A moment later, the prong begins to move
from ‘B’ to ‘A’.
The pressure in the adjacent layer
decreases and refraction is produced. This
rarefaction is transferred to the air layer
next to it and so on.
10. As the tuning fork moves back and forth
rapidly, a series of compression and rarefaction
are created in the air .
In this way sound waves propagates through
the air.
11. Pitch:- Pitch is the characteristic of sound by which
we can distinguish between a shrill and a grave
sound.
12.
13. The pitch of sound depends upon
the frequency of sound. Greater value of
frequency, larger is the value of pitch of
sound.
14. The frequency of ladies and children is
greater than that of men, so voice of ladies
and children is shrill and of high pitch.
Where as the sound of men is grave due to
low pitch.
The both pitch and frequency have same
unit that is hertz.
15.
16. Loudness is the characteristic of
sound by which loud and faint sounds
can be distinguished.
When we talk to our friends, our voice
is low, but when we address a public
gathering our voice is loud.
Loudness of a sound depends upon
following factors.
17. Amplitude of the vibrating body
The loudness of the sound varies
directly with the amplitude of the
vibrating body.
The sound produced by the sitar will
be loud if we pluck its wires more
violently.
Similarly, when we beat a drum
forcefully, the amplitude of its
membrane increases and we hear a
loud sound.
18. Area of the vibrating body
The loudness of the sound depends
upon the area of the vibrating body.
For example, sound produced by a
large drum is louder than that by
small one because of its large
vibrating area.
We can conclude that the loudness
increases with the area of the
vibrating body.
19. Distance from the vibrating body
Loudness of sound also depends
upon the distance of the vibrating
body from the listener. It is caused by
the decrease in amplitude due to
increase in distance.
Loudness also depends upon the
physical condition of the ears of the
listener.
20. LOUDNESS
Loudness is the characteristic of sound by
which loud and faint sounds can be
distinguished.
The magnitude of auditory sensation is
called loudness.
21.
22. Quality of sound
The characteristic of sound by which two
sounds of same intensity and of same
pitch can be distinguished is called quality
of sound.
We can easily distinguish between the
sound of flute and piano. It is due to
different quality of these two sounds.
We recognize the voice of relative/friend
over the cell phone by quality.
23.
24. Acoustic Protection
The technique or method used to absorbed
undesirable sounds by soft and porous surfaces is
called acoustic protection.
25. Noise barriers, made up of modular panels,
provide a more efficient sound block than
other sound reduction materials such as
concrete, metal or wood.
26.
27. Reflection of sound is more prominent
if the surface is rigid and smooth, and
less if the surface is soft and irregular.
Soft materials absorb large amount of
sound energy. By using such materials
in noisy places we can reduce the level
of noise pollution.
If the surface of classrooms are too
absorbent, the sound level may be low
for the audience.
28. Sometimes, when sound reflects from the
walls, ceiling and floor of a room, the
reflecting surfaces are too reflective and the
sound becomes garbled due to multiple
reflections.
29. noise is nuisance
We perceive sound as noise or music.
Unpleasant sound is called noise and pleasant
sound is called music.
30.
31. Noise is unwanted sound that can
greatly affect your quality of life and health if
continually exposed to it. It can also result
in headaches, sleep deprivation and stress,
among others. Everyone has a different
tolerance threshold when it comes to noise
but it is unrealistic to expect complete
silence.
32. There are many types of noise that we can
easily avoid or reduce:
home entertainment equipment and loud
music
parties
noise from the neighbors
noisy animals/ barking dogs
Do-It-Yourself work and domestic appliances
car and house alarms
noise from refrigerated units in shops
ventilation fans
local pubs and entertainment
33. The loud sound of radio television,
slamming of door, rumbling of truck,
road traffic and sound from neighbor
is a noise pollution that can be
reduced to some extent and some
measure should be taken in this
regard to save ourselves from this
pollution which is unpleasant
disagreeable and headache.
34. reflection of sound may produce echo
Hard surfaces such as walls will
reflect sound which we hear a short
time after the original sound is called
echo.
35. Echo can be used to calculate
the speed of sound let one is standing
at a distance of 100 m from a high
wall and clap two wooden block to
gather at a such rate that each clap
coincide with the echo of the one
before calculating the time for one
echo we can determine the velocity of
sound.
V = 2d/t
36. Audibility
The word “audibility” comes from the
word “audible” which means ‘can be heard’.
The range of frequencies which a listener can
hear is known as the range of audibility.
39. A normal human ear can hear a
sound only if its frequency lies
between 20Hz and 20,000Hz.
In other words, a human ear neither
hears a sound of frequency less than
20Hz nor a sound of frequency less
than 20,000 Hz. Different peoples
have different range of audibility.
40. use of ultrasound
Ultrasound is an
oscillating sound pressure wave with
a frequency greater than the upper
limit of the human hearing range.
Sound waves with frequency above
2000Hz are called ultrasonic waves
cannot be heard but can be detected
electronically and displaced on
cathode ray oscilloscope.
41.
42. Uses of ultrasound
They are used to detect objects.
They are used to measure distances.
They are used to Ultrasonic imaging.
They are used to veterinary medicine.
They are used to human medicine.
They are used to cleaning of chemicals.
They are used to mixing of chemicals.
They are used to accelerate chemical
processes.
They are used to monitor health and some
time to determine the position of unborn
baby.
43. Ultrasound can also be used in
ultrasonic drill to cut holes in hard
mated rails such as glass steel and
jeweler.
Ultrasound pluses are being used to
distinguish minor tumors and kindly
stones.
In medical ultrasound is preferred
over x- rays as it is less hazardous
due to its low energy.
