The document covers the fundamental aspects of sound, including its nature, propagation, characteristics, and how it interacts with matter. Key topics discussed are the speed of sound, intensity and decibel measurements, and phenomena such as interference and the Doppler effect. The ear's functioning and the differences between decibels and hertz are also explained, emphasizing the significance of sound in both physical and perceptual contexts.

1. JAI HIND
Virendra Kumar Maurya
Assistant Professor
CAEHS COLLEGE, MEERUT
SOUND OF PHYSICS

2. Index
• Sound
• Nature and propagation of sound wave
• Characteristics of sound
• Speed of sound in a material medium
• Intensity of sound
• The decibel
• Interference of sound waves
• Beats
• Diffractions
• Wave theory
• Doppler ,s effect

3. sound
• Sound is a form of energy that can be heard
and travels in waves.
• When matter vibrates or moves back and forth
very quickly, a sound is made.
• Sound waves can travel through solids, liquids,
or gases.
• Example: When a school bell rings, parts
of the bell will vibrate creating sound.

4. Sound in human
• We use our vocal cords to make
sounds in our throat.
• When we speak, our vocal cords
vibrate.
• Place your hand on your throat
when you talk, and you can feel
the vocal cords vibrate.

5. How does the ear work?
Sound Waves
 Sound waves are sent.
 The outer ear “catches the sound waves”.
 The middle ear takes the sound waves and “vibrates”
the eardrum.
 The inner ear sends the messages to the brain.
Middle Ear
Inner Ear
 The brain puts it together you can understand the
sounds.
Outer Ear

8. Nature and propagation of sound wave
• Sound is a sequence of waves of pressure
which propagates through compressible
media such as air or water. (Sound can
propagate through solids as well, but there are
additional modes of propagation). During
their propagation, waves can be reflected,
refracted, or attentuated by the medium.

9. • The purpose of this experiment is to examine what effect
the characteristics of the medium have on sound. All media
have three properties which affect the behavior of sound
propagation:
 A relationship between density and pressure. This
relationship, affected by temperature, determines the
speed of sound within the medium.
 The motion of the medium itself, e.g., 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. This determines the rate at
which sound is attenuated. For many media, such as air or
water, attenuation due to viscosity is negligible.

10. Characteristics of sound waves
 Amplitude - The strength or level of sound pressure is
called amplitude.
 Wavelength - The physical gap between two consecutive
maxima of an acoustic source is called the wavelength
 Frequency - The number of periodicals compressing and
rarefaction cycles that occur a single second when the
beam is transmitted across the medium is called frequency.
 Speed - The rate during which waves move through a
medium is called sound speed.
 Timbre - The quality that allows sounds of identical
frequency to be distinguished is called timbre.(Timbre, also
known as tone color or tone quality)

11. Amplitude of sound

13. Frequency of sound

14. Speed of sound

16. Timbre of sound

17. Speed of sound

18. Intensity of sound
• Sound intensity, also known as acoustic
intensity, is defined as the power carried by
sound waves per unit area in a direction
perpendicular to that area. The SI unit of
intensity, which includes sound intensity, is
the watt per square meter (W/m2).

20. Decibel
Decibel is the unit of sound. Its symbol is 'dB'. We can
define decibel as.
Named after the inventor Alexander Graham Bell,
a decibel (dBA) is the unit used to express the intensity
of sound.
It is normally measured using the “A” scale, which
approximates the human ear’s response to a wide
range of frequencies.
A decibel is a logarithmic value to the base 10.
Readings are given as dB(A) or dBA. Therefore, if the
decibel value is increased by 10, the noise exposure
has doubled.

21. A normal conversation takes place at about 60
decibels.
A woodshop noise level is about 100 decibels,
and a chainsaw noise measures about 110
decibels.
 Prolonged exposure to noise above 85
decibels can cause hearing loss.

23. difference between decibels and hertz
• Decibels (dB) and hertz (Hz) are both units of measurement for
sound, but they measure different aspects of sound:
• Decibels
• Measure the loudness or intensity of sound. The more decibels a
sound has, the louder it is. The decibel scale is logarithmic and uses
the human hearing threshold of 20 µPa as a reference level.
• Hertz
• Measure the frequency of sound, or the number of vibrations per
second. A higher frequency corresponds to a higher-pitched
sound. Hertz are also used to measure the frequency of
electromagnetic radiation, such as the 60 hertz frequency of the US
household electrical supply. Hertz are also commonly used to
describe periodic waveforms and musical tones, as well as the clock
speeds of computers and other electronics.

24. 2ND CLASS

25. Interference of sound waves
When two or more sound waves from
different sources are present at the same
time, they interact with each other to produce
a new wave.
The new wave is the sum of all the different
waves. Wave interaction is called interference.

26. If the compressions and the rarefactions of the
two waves line up, they strengthen each other
and create a wave with a higher intensity. This
type of interference is known as constructive.

27. When the compressions and rarefactions are
out of phase, their interaction creates a wave
with a dampened or lower intensity. This
is destructive interference

28. Dead spots
• This place no sound at all can be heard. Dead
spots occur when the compressions of one
wave line up with the rarefactions from
another wave and cancel each other.

29. Beats
A wave not only travels in space, but it also
propagates through time, so if the two waves
can produce interference by overlapping in
space, they should also produce an
interference pattern when they overlap in
time; this phenomenon is called beats.

32. Diffraction
• the bending of waves around small* obstacles
and the spreading out of waves beyond small*
openings.
• the spreading of waves around obstacles.
Diffraction takes place with sound; with
electromagnetic radiation, such as light, X-
rays, and gamma rays; and with very small
moving particles such as atoms, neutrons, and
electrons, which show wavelike properties.

33. Diffractions

34. WAVE THEORY
• In the late 17th century, scientists were embroiled in a
debate about the fundamental nature of light –
whether it was a wave or a particle.
• Sir Isaac Newton strongly advocated the particle nature
of light.
• But, the Dutch physicist Christiaan Huygens believed
that light was made up of waves vibrating up and down
perpendicular to the direction of the wave propagation
and therefore formulated a way of visualizing wave
propagation.
• This became known as ‘Huygens’ Principle‘.

35. • The wave theory of light proposed by Christian
Huygens has stood the test of time, and today,
it is considered the backbones of optics. Here,
in the article, let us discuss the wave theory of
light in detail.

36. • Historical Context
• Christiaan Huygens: Proposed the wave theory of
light in the 17th century, suggesting that light
behaves as a wave.
• Thomas Young: Demonstrated the wave nature
of light through his double-slit experiment in the
early 19th century.
• Augustin-Jean Fresnel: Developed a
mathematical basis for wave optics, explaining
diffraction and interference.

37. DOPPLER’S EFFECT
• The Doppler effect (also Doppler shift) is the change in
the frequency of a wave in relation to an observer who
is moving relative to the source of the wave.
• The Doppler effect is named after the
physicist Christian Doppler, who described the
phenomenon in 1842.
• A classic illustration of Doppler shift is the pitch shift
that occurs when a car approaches and moves away
from an observer while sounding its horn. The received
frequency is higher during approach, the same as it
passes by, and lower during the recession than the
emitted frequency.

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12. SLIDESHARE
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