This presentation is for students of class 8th and 9th

2. Sound is a sensation or feeling
that we hear. We produce
sounds by doing something. The
motion of materials or objects
causes vibrations. A sound
originates in the vibration of an
object, which makes the air or
another substance around the
object vibrate. The vibration of
the air moves outward in all
directions in the form of a wave
In a drum sound is produced
when its membrane vibrates

4. The human voice is produced in the
larynx, which is a part of the throat.
There are two small pieces of tissue
that stretch across the larynx with a
small opening between them, these
tissues are our vocal cords. As we
speak, muscles in our larynx tighten
the vocal cords making this small
opening become narrower. When air
from our lungs passes through the
tightened cords a vibration is
produced. This vibration produces
vocal sounds. The tighter the vocal
cords, the more rapidly the vocal
cords vibrate and the higher the
sounds that are produced. This is
what causes the human voices to
have different pitches.6

5. Animals also produce sounds. Almost all
mammals, birds, and frogs have vocal
cords or similar structures, which allow
them to produce sounds in a similar way
to humans. However, many other animals
produce distinctly different sounds. For
example, bees buzz as they fly because of
the rapid movement of their wings. Their
wings make the air vibrate producing a
buzzing sound. A cricket produces a
singing type sound as it scrapes parts of
its front wings together. Some types of
shellfish produce clicks by tapping their
claws together.7

6. Musical instruments produce many different sounds in various ways. There
are three categories of musical instruments, percussion, string, and wind
Some instruments need to be
struck by an object in order to
produce a sound, these are
called percussion instruments.
For example when the
membrane of a drum is hit the
membrane vibrates, producing
a sound, or when a bar of a
xylophone is struck, a sound is
produced. Each bar of a
xylophone produces a different
note when struck.

7. String instruments, such as a
harp or violin, produce
sounds when one or more of
their strings are
plucked, causing them to
vibrate. This vibration causes
parts of the body of the
instrument to vibrate, creating
sound waves in the air. The
pitch of a stringed instrument
depends upon the string's
thickness, its length, the
distance stretched, and the
number of times it vibrates.

8. Wind instruments, such
as a flute or trumpet
produce sound when a
column of air inside the
instrument vibrate. For
example, with a trumpet
it is the vibrating lips of
the player which makes
the air column vibrate

10. A sound wave is a transfer of energy as it
travels away from a vibrating source. Sound
waves are formed when a vibrating object
causes the surrounding medium to vibrate.
A medium is a material (solid, liquid or gas)
which a wave travels through. As sound
waves move through a medium the
particles vibrate forwards and backwards. A
sound's volume, how loud or soft it
is, depends on the sound wave. The more
energy put into making a sound or a sound
wave, the louder the volume will be. The
father a sound wave travels, the more it
spreads, this makes it more difficult for us to
hear a sound. So the nearer you are to a
sound the louder it sounds to us. A sound
wave enters the ear and is changed into
nerve signals, which are interpreted by the
brain.12

11. Sound is transmitted through
gases, plasma, and liquids as
longitudinal waves, also called
compression waves. Through
solids, however, it can be
transmitted as both longitudinal
waves and transverse waves.
Longitudinal sound waves are longitudinal
waves of alternating pressure waves
deviations from the equilibrium
pressure, causing local regions
of compression and
rarefaction, while transverse
waves (in solids) are waves of
alternating shear stress at right
angle to the direction of
propagation.
Transverse waves

12. The behavior of sound propagation is generally
affected by three things:
A relationship between density and pressure. This
relationship, affected by temperature, determines
the speed of sound within the medium.
The propagation is also affected by the motion of
the medium itself. For example, sound moving
through wind. Independent of the motion of sound
through the medium, if the medium is moving, the
sound is further transported.
The viscosity of the medium also affects the motion
of sound waves. It determines the rate at which
sound is attenuated. For many media, such as air
or water, attenuation due to viscosity is negligible.

13. Sound waves are often simplified to a description in
terms of sinusoidal plane waves, which are characterized
by these generic properties:
Frequency, or its inverse, the period
Wavelength
Wave number
Amplitude
Sound pressure
Sound intensity
Speed of sound
Direction

14. The perception of sound in
any organism is limited to a
certain range of frequencies.
For humans, hearing is
normally limited to
frequencies between about
20 Hz and 20,000 Hz (20
kHz)although these limits
are not definite. The upper
limit
Generally decreases with
age
Human hearing system

15. As a signal perceived by one of the
major senses, sound is used by many
species for detecting danger,
navigation, predation, and
communication. Earth's atmosphere,
water, and virtually any physical
phenomenon, such as fire, rain, wind,
surf, or earthquake, produces (and is
characterized by) its unique sounds.
Many species, such as frogs, birds,
marine and terrestrial mammals, have
also developed special organs to
produce sound. In some species, these
produce song and speech. Furthermore,
humans have developed culture and
technology (such as music, telephone
and radio) that allows them to generate,
record, transmit, and broadcast sound.
The scientific study of human sound
perception is known as
psychoacoustics.

16. Sound is a sequence of
waves of pressure that
propagates through
compressible media
such as air or water.
(Sound can propagate
through solids as well,
but there are additional
modes of propagation).
During propagation,
waves can be reflected,
refracted, or attenuated
by the medium.[2]

17. Wavelength: The distance between any point on a
wave and the equivalent point on the next phase.
Literally, the length of the wave.

18. Amplitude: The strength or power of a wave signal.
The "height" of a wave when viewed as a graph.
Higher amplitudes are interpreted as a higher
volume, hence the name "amplifier" for a device which
increases amplitude.

19. Frequency: The number of times the wavelength
occurs in one second. Measured in kilohertz (Khz), or
cycles per second. The faster the sound source
vibrates, the higher the frequency.
Higher frequencies are interpreted as a higher pitch. For
example, when you sing in a high-pitched voice you are
forcing your vocal chords to vibrate quickly.

20. Sound travels at 330 meters per second or 740 miles per hour.
Sound travels the fastest through solids and the slowest through
gases. The faster an object vibrates the higher the frequency, which
causes the pitch of the sound to be higher. The higher the frequency
sounds come from shorter wavelengths. A wavelength is one aspect
of a sound wave. A wavelength is the length of one cycle of sound.
The period of a sound wave is the time taken for one wavelength to
pass a certain point before a new wave begins to pass by. Longer
wavelengths have a lower pitch. The lowest tones that your ears can
hear are about 16 vibrations per second, or 16 Hz. Amplitude
specifies the sound's loudness. A low amplitude will produce a soft
sound and a higher amplitude will produce a louder sound.14

21. The speed of a sound wave refers
to how fast the disturbance or wave
is passed from particle to particle.
Since the speed of a wave is
defined as the distance which a
point on a wave travels per unit of
S = 330 meter/seconds
time, it is often expressed in units
S = (330 X 60 X 60 X 3.3)/5280
of meters/seconds (m/s). The
S= 330M/s X 3.3ft./M X 3600sec/hr
speed of any wave depends upon
X 1 mile/5280ft.
the properties of the medium
through which the wave is traveling.
The density of the medium will
affect the speed the wave will travel
at. A sound wave will travel faster in
a less dense material rather than in
a more dense material. The
equation for the speed of sound is
speed = distance/time.

22. DURATION
This is probably the quality
that is simplest to relate to a
measureable quantity: the
duration of a sound is the
time interval between its
beginning and end points.
Our hearing system is
capable of detecting and
distinguishing a very short
sound, even if it contains
only a few cycles of air
pressure oscillation.

23. LOUDNESS
Another attribute of sound
that is easily quantified is
loudness. It is related to
the amplitude of the
pressure oscillation in a
sound wave. Our
perception extends over
such a broad range of
amplitudes (with the
perceptible limits
depending on frequency)
that we use a logarithmic
scale.

24. Noise pollution is excessive, displeasing
human, animal or machine-created
environmental noise that disrupts the
activity or balance of human or animal life.
The word noise comes from the Latin
word nauseas, meaning seasickness.
The source of most outdoor noise
worldwide is mainly construction and
transportation systems, including motor
vehicle noise, aircraft noise and rail
noise.Poor urban planning may give rise
to noise pollution, since side-by-side
industrial and residential buildings can
result in noise pollution in the residential
area.

25. Noise health effects are both health and behavioral in
nature. The unwanted sound is called noise. This
unwanted sound can damage physiological and
psychological health. Noise pollution can cause annoyance
and aggression, hypertension, high stress
levels, tinnitus, hearing loss, sleep disturbances, and other
harmful effects. Furthermore, stress and hypertension are
the leading causes to health problems, whereas tinnitus
can lead to forgetfulness, severe depression and at times
panic attacks.
Chronic exposure to noise may cause noise-induced
hearing loss. Older males exposed to significant
occupational noise demonstrate significantly reduced
hearing sensitivity than their non-exposed peers, though
differences in hearing sensitivity decrease with time and
the two groups are indistinguishable by age 79. A
comparison of Maaban tribesmen, who were insignificantly
exposed to transportation or industrial noise, to a typical
U.S. population showed that chronic exposure to
moderately high levels of environmental noise contributes
to hearing loss.

26. High noise levels can
contribute to cardiovascular
effects and exposure to
moderately high levels during
a single eight hour period
causes a statistical rise in
blood pressure of five to ten
points and an increase in
stress and vasoconstriction
leading to the increased blood
pressure noted above as well
as to increased incidence of
coronary artery disease.
Noise pollution is also a cause
of annoyance. A 2005 study
by Spanish researchers found
that in urban areas
households are willing to pay
approximately four Euros per
decibel per year for noise

27. Technology to mitigate or remove noise can be
applied as follows:
There are a variety of strategies for mitigating
roadway noise including: use of noise
barriers, limitation of vehicle speeds, alteration
of roadway surface texture, limitation of heavy
vehicles, use of traffic controls that smooth
vehicle flow to reduce braking and
acceleration, and tire design. An important factor
in applying these strategies is a computer model
for roadway noise, that is capable of addressing
local topography, meteorology, traffic operations The sound tube designed to
and hypothetical mitigation. Costs of building-in reduce roadway noise
mitigation can be modest, provided these without distracting from the
solutions are sought in the planning stage of a area's aesthetics.
roadway project.