I made it for class lX physics chapter sound. I hope it may helpful for u . BY: AJAY lx RISY

2. 1.It’s a disturbance that travels through a medium.
2.Sound travels in a longitudinal wave with the molecules
of the medium close in a compression and farther away in a
rare reaction.
3.Sound wave can travel in gas, liquid and solid, but not in
outer space because there are no molecules for compression
or rarefaction to transmit waves

3. Sound waves are collected by the pinna and then are directed
through ear canal sound waves on striking the eardrum make it
vibrate exactly the same way as the given sound emitting object.
The bones in the middle ear start vibrating when
eardrum vibrates. It helps in magnifying the vibrations. When
the magnified vibrations reach the cochlea in the inner ear, the
fluid in it starts vibrating. These vibrations are picked up by
sensory receptors and are converted into electrical signals. These
electrical signals then travel to the brain which interprets sound.

4. • Human beings can hear sound frequencies between 20 Hz
and 2000 Hz.
• Sound whose frequency is less than 20 Hz is called
infrasonic sound
• Sound whose frequency is more than 2000 Hz is called
ultrasonic sound

5. • Ultrasonic sound is used to clean objects like electronic
Components, used to detect cracks
• in metal blocks, used in ultra sound scanners for getting
images of internal organs of the
• human body used to break small stones formed in the
kidneys into fine grains

6. To produce pleasant sounds, a number of musical instruments
have been developed. Some instruments produce sound due to the
vibration of membranes, some due to the vibration of strings, and
some others produce sound due to the vibration of an air column.
The to and fro or back and forth motion of an object is called
vibration. The sitar, veena , violin, guitar and ektara are some
stringed instruments. The table , cymbals, ghatam, kartal and
manjira are some instruments that work on the vibration of a
membrane, and instruments like the flute and the trumpet
produce sound due to the vibration of an air column present in
them.

7. • In longitudinal waves, particles of the medium vibrate
parallel to the direction of propagation of the
waves.Wavelength (l) is the distance between two
consecutive compressions or two consecutive rarefactions
in longitudinal waves. Time period (T) is the time interval
between two consecutive compressions or two consecutive
rarefactions in longitudinal waves.

8. • In transverse waves, particles of the medium vibrate
perpendicular to the direction of propagation of waves .
Wavelength (l) is the distance between two consecutive crests or
two consecutive troughs in transverse waves. Time period (T) is
the interval between two successive compressions or two
successive rarefactions in longitudinal waves. Time period (T) is
the interval between two successive crests or two successive
troughs in transverse waves.

10. • 1. The particles of medium vibrate in the same
direction.
2. They are possible in all kinds of media.
3. They consists of regions of compression and
rarefaction.
4. They cannot be polarised.
5. Sound waves in air is an example of longitudinal
waves.

11. • 1. The particles move at right angles to the direction of
wave propagation.
2. They are possible only in solids.
3. They consists of crests and troughs.
4. They can be polarised.
5. Vibrations in a string is an example of transverse waves.

12. Sound Waves Light Waves
1. Longitudinal waves travel with a speed of 330 m s-1
2.Require a medium to propagate.
3. Sounds waves are produced by oscillating particles of
medium.
1. Transversal waves travel with a speed of 3 x 108 m s-1
2.Do not require a medium to propagate.
3. Light waves are produced by oscillating charged particles of
medium

13. • Music is a pleasant sound, whereas noise is un
pleasant to hear. The waveform of musical sound
is periodic and regular whereas the waveform of
of noise is irregular and sudden.
The frequencies that make up a musical sound are
in the ratio of small whole numbers whereas this
is not the case for noise.

14. • Loudness the property by virtue of which a loud sound can be distinguished from a
faint one, both having the same pitch and quantity.
LOUDNESS IS :
i) directly proportional to square of amplitude.
ii) inversely proportional to square of distance.
iii) directly proportional to surface area of vibrating body.
iv) directly proportional to the density of medium.
v) more the resonant bodies nearby , more will be the loudness.

15. • Intensity of sound is the amount of sound energy
incident per unit time per unit area . Intensity is a
measurable quantity whereas loudness is sensation.
L = K log I , Where
L = Loudness
I = Intensity
K = Constant
• Intensity is proportional to (i) square of
amplitude (ii) square of frequency (iii) density of

16. • The characteristic of sound by which an acute or shrill note can be
distinguished from a flat or grave note is called Pitch. The frquency of note
produced by a string in stringed instruments can be changed by changing the
place of plucking or by increasing the tension on the string or by using the
string of less or more thickness.
Pitch of sound depends on:
(i) frequency (ii) relative motion between sourse and listner. Pitch is sensation
only.

17. • Quality or Timbre of a sound is that characteristic which
distinguishes the two sounds of same pitch and loudness
but emitted by two different instruments. It depends on
waveform. The waveform of a sound from an instrument
depends on the presence of subsidiary vibrations along with
the principal vibration and the relative amplitudes of various
subsidiary vibrations in relation to principal vibration.

18. • The direction in which the sound wave is incident and the direction, in
which it is reflected, make equal angles with the normal to the reflecting
surface, at the point of incidence.
The incident sound wave, the reflected wave and the normal at the point
of incidence are in the same plane.
Sound waves need polished or rough surfaced obstacles to get
reflected. The incident sound wave, the reflected sound wave and the
normal, all lie in the same plane.

19. • An echo is the repetition of sound that results as a reflection
from a surface. Multiple reflection of sound is the successive
reflection of sound from various reflecting surfaces. We cannot
hear an echo unless the reflecting surface is beyond a specified
distance from the source of the sound. The sensation of sound
persists for 0.1 second. The minimum distance required to hear
an echo is 17.2 metres.

20. • The persistence of sound in big enclosures like auditoriums is the
result of repeated reflections of sound and is called reverberation.
Reverberation can be minimized by using sound absorbent
materials like cardboard, thick curtains and fibre. The process of
multiple reflection of sound is applied in:
• Stethoscope
• Megaphones
• Horns
• Trumpets

21. • The outer ear. is called pinna. It collects the sound from the surroundings.
The collected sound passes through the auditory canal, there is a thin
membrane called eardrum. When a compression of the medium reaches the
eardrum, the pressure on the outside of the membrane increases and forces
the eardrum inward. Similarly, the eardrum moves outward where a
rarefaction reaches it. In this way eardrum vibrates.

22. • A sonar which stands for Sound Navigation and
Ranging is technique used for determining the depth
and also locating underwater objects such as reefs,
submarines etc.
In this method, to find the depth of ocean, a strong
ultrasonic wave is sent from the ship towards the
bottom of the ocean. This ultrasonic is received back
after it is reflected from the bottom of the sea

23. • Echo is the reflection of a sound or some other wave off a surface. Reverberation is
the sound or the pattern created by the superposition of such echoes.
• An echo can be heard only when the distance between the source of sound and the
reflecting body is at least 17 m. A reverberation can occur when sound wave is
reflected by a nearby wall also.
• An echo is usually clear and can be clearly distinguished. A reverb is not a clear replica
of the original sound sample.
• Echo can be used to determine the distance of a reflecting object such as a large
building or a mountain, if the ambient temperature is known. Reverberation cannot
be utilized for distance measurement applications.
• An echo can be heard both in open and closed spaces. Reverberation is usually
experienced in closed spaces with multiple reflecting objects.

25. Sound waves are often characterized by four basic qualities,
though many more are related:
Frequency, Amplitude, Wave shape and Phase*
Some sound waves are periodic, in that the change from
equilibrium (average atmospheric pressure) to maximum
compression to maximum rarefaction back to equilibrium is
repetitive. The 'round trip' back to the starting point just described
is called a cycle. Periodic motion is classically demonstrated by
the up and down motion of a dropped weight (mass) attached to a
spring or by observing the motion of a pendulum. The amount of
time a single cycle takes is called a period.

27. • The wavelength of a wave is the distance between a
point on one wave and the same point on the next
wave. It is often easiest to measure this from the
crest of one wave to the crest of the next wave, but
it doesn't matter where as long as it is the same
point in each wave.