2. THE NATURE OF SOUND
WAVES
Sound is a form of energy propagated as waves that make our eardrums
vibrate.
Sound waves are longitudinal waves which is required a medium for its
propagation.
Sounds are produces by vibrations such as the vibrations of the coneshaped diaphragm of loudspeaker, guitar strings, column of air in a musical
instrument a tuning fork
Sound waves cannot travel in a vacuum because there is no
medium(particles) through which the sound energy can be propagated.
3. How is sound produced by a vibrating
objects?
When a tuning fork vibrates, layers of air vibrate and the
sound energy is propagated through the air around it in the form
of waves.
• When the tuning fork moves forwards, the air is compressed.
• When the tuning fork moves backwards, the air layers are
pulled apart and cause a rarefaction.
• Therefore, a series of compression and rarefactions will
produce sound.
4. Why does sound waves is a
longitudinal waves?
The air particles vibrate backward and forward in the direction
parallel to the direction of propagation of the sound wave.
• Wavelength of sound, λ = the distance between two
successive regions of compression or two successive regions of
rarefaction.
6. LOUDNESS & AMPLITUDE OF
SOUND
The loudness of a sound is considered to be
high or otherwise depending on the hearing
ability of a person.
Loudness is influenced by the amplitude of
the sound wave.
7. PITCH & FREQUENCY OF
SOUND
The pitch of a sound or a musical note is an indication of
how high or low the sound is.
The pitch of a sound is determined by its frequency :
a high pitch corresponds to a high frequency.
8.
9. A P P L I C AT I O N S O F S O U N D WAV E S
Cleaning with Ultrasonic Waves
- Dentist use ultrasonic waves to removes plaque
from teeth
Locating an object under water
- SONAR is a system used to detect underwater
objects or to determine the
depth of the water by
mean of an echo.
- Ultrasound signal is sent out from a transmitter.
- Its echo from the seabed is detected by a receiver
which is connected to an
electrical recording circuit.
- The time interval, t between the sending and
receiving of the ultrasound
signal after
reflection from the seabed is measured.
10. Disintegration of kidney stones
- sound waves of high energy are directed at the kidney
stones to destroy them in the cavity of the kidney.
A bat can navigate in darkness
When ultrasonic waves emitted by the bat hit an
object, they are reflected back and received by the
bat.
The time between the emission of the sound waves
and reception of the reflected waves enables the bat
to estimate the position of the object accurately.
This enables the bat to adjust its direction to avoid
knocking at the object.
12. EXAMPLE
1. a student is standing at a distance of 45 m
from a wall. He gives loud clap and the echo
is heard after 0.3 s, calculate the speed of
sound in air.
13. An ultrasonic wave is used to determine the depth of a
seabed. A pulse of ultrasound is generated and travels
to the seabed and reflected by it. The time taken by
a pulse of ultrasonic wave to travel to and fro the
seabed is 0.28 s. It the speed of sound in the water
is 1 500 ms-1, calculate the depth of the seabed.
