Reflection of Sound - Sound, CBSE Class 9 Science Video Lecture

reflection of sound sound is a part of
our everyday sensory experience so how
is sound produced propagated and
detected a good model is the stethoscope
used to listen to the sounds of heart
and lungs but how are these sounds heard
to understand this we need to know what
reflection of sound is when sound
travels through a medium it strikes the
surface of another medium and bounces
back to the original medium this
phenomenon is called the reflection of
sound which obeys the laws of reflection
the first law states that the angle of
incidence is equal to the angle of
reflection we can provide this by
placing two tubes at certain angles on a
wooden board if a clock is placed near
the end of one of the tubes we can hear
the sound waves through the second tube
by adjusting it to get the sound at its
maximum we can see that the angle of
incidence is equal to the angle of
reflection the second law states that
the incident wave the reflected wave and
the normal at the point of incidence all
lie in the same plane sound waves also
suffer reflection from large obstacles
if we stand at a distance from a high
wall and clap our hands we can hear the
same clapping sound off to the dying out
of the original sound this is called an
echo
therefore for an echo to be heard the
time interval between two sounds must be
0.1 seconds as sound travels at the
speed of 340 meters per second layer the
distance traveled by sound in 0.1
seconds is 34 meters therefore to hear
an echo we need to stand at least 17
meters away from the wall now what
happens if there are four enclosed walls
that are less than 17 meters away what
we experience here is a reverberation
that is due to multiple reflections of
sound from the walls roof and floor
which follow so closely behind the
original sound that the original sound
appears to be prolonged even when the
source of the sound stops we can thus
see that reparation is the multiple
reflections of sound waves
whereas echo is the single reflection of
sound waves however excessive
reverberation makes the sound indistinct
which can be as set back in auditoriums
this can be reduced by using sound
absorbing materials like ceilings made
of soft and textured materials and
flooring made of acoustic tiles certain
technologies make use of the multiple
reflections of sound to name a few we
have megaphones hearing aids sound
boards stethoscopes and the curved
ceiling of concert halls
now back to our stethoscope the
stethoscope picks up multiple
reflections of sound from the patient's
body
this causes the flat surface of the
diaphragm to vibrate each wave bounces
or reflects off the inside walls of the
rubber tube in this way each wave in
succession reaches the ear tips on the
ends of the device and finally to the
listeners ear drums and the doctor
interprets the sound he hears things to
remember the property of sound to bounce
back from the surface on which it falls
is known as the reflection of sound echo
is hard only the minimum distance
between the source of sound and the
obstacle is 17 meters reverberation is
multiple reflections of sound after the
original sound is produced the first law
of reflection states that the angle of
incidence is equal to the angle of
reflection the second law states that
the incident wave the reflected wave and
the normal at the point of incidence all
lie in the same plane
you