Meaning of sound
The generation and propagation of a
Sound created from a vibrating string
Nature of sound
Sound properties and their perception
Amplitude and intensity
Speed of sound indifferent media
Behavior of sound
is a disturbance that is transported
through a medium via the mechanism
of particle-to- particle interaction.
is a wave that is created by vibrating
objects and propagated through a medium
from one location to another.
is a mechanical wave.
The vibrations of the object set particles
in the surrounding medium in vibration
motion, thus transporting energy through
the medium. For a sound wave traveling
through air, the vibrations of the particles
are best described as longitudinal.
Compressions are regions of high air pressure.
Rarefactions are regions of low air pressure.
The diagram below depicts a sound wave created by a tuning
fork and propagated through the air in an open tube.
1. There is a medium that carries the disturbance
from one location to another.
2. There is an original source of the wave,
vibrating object capable of disturbing the first
particle of the medium.
3. The sound wave is transported from one
location to another by means of
refers to “how often” the air particles vibrate.
The sensation of a frequency is commonly referred
to as the pitch of a sound.
A high pitch sound corresponds to a high frequency
sound wave and a low pitch sound corresponds
to a low frequency sound wave.
Any sound with a frequency below the audible
range of hearing(i.e., less than 20 Hz) is known as an
infrasound and any sound with a frequency above
the audible range of hearing (i.e., more than 20 000 Hz)
is known as an ultrasound.
( 50 Hz – 45 000 Hz )
( 45 Hz – 85 000 Hz )
( > 120 000 Hz )
( > 200 000 Hz )
( 5 Hz – 10 000 Hz )
( 20 Hz – 20 000 Hz )
The amount of energy that is transported past a given area of the
medium per unit of time is known as the intensity of the sound
The greater the amplitude of vibrations of the particles of the
medium, the greater the rate at which energy is transported
through it, and the more intense that the sound wave is.
Intensity is the energy/time/area; and since the energy/time ratio
is equivalent to the quantity power, intensity is simply the
Typical units for expressing the intensity of a sound wave are
The scale for measuring intensity is the decibel
The faintest sound that a human ear can detect is
known as the threshold of hearing.
While the intensity of a sound is a very objective
quantity that can be measured with sensitive
instrumentation, theloudness of a sound is more of a
subjective response that will vary with a number of
Despite the distinction between intensity and
loudness, it is safe to state that the more intense
sounds will be perceived to be the loudest sounds.
Speed of sound, (m/s)
1. Reflection of Sound
Reflection of sound waves off of surfaces can
lead to one of two phenomena - an echo or a
An echo is produced in an empty room.
A reverberation often occurs in a small room
with height, width, and length dimensions of
approximately 17 meters or less.
2. Refraction of Sound
Sound waves are known to refract when
traveling over water.
3. Diffraction of Sound Waves
Sound waves moving around corners or edges.
4. Interference of Sound Waves
refers to the rate at which the volume is heard to
be oscillating from high to low volume.
can be described as the effect produced by a
moving source of waves in which there is an apparent
upward shift in frequency for the observer and the
source are approaching and an apparent downward
shift in frequency when the observer and the source
On a hot summer day, a pesky little
mosquito produced its warning sound near your
ear. The sound is produced by the beating of its
wings at a rate of about 600 wing beats per
a. What is the frequency in Hertz of the sound
b. Assuming the sound wave moves with a
velocity of 350 m/s, what is the wavelength of
Check Your Understanding
Identify the following statements whether TRUE
1. A sound wave is a mechanical wave.
2. A sound wave is a means of transporting
energy without transporting matter.
3. Sound can travel through a vacuum.
4. A sound wave is a transverse wave.
5. To hear the sound of a tuning fork, the tines
of the fork must move air from the fork to
6. Intense sounds are usually perceived as loud
7. The speed of a sound wave depends upon its
frequency and its wavelength.
8. Sound waves would travel faster on a warm
day than a cool day.
9. A high pitched sound has a low wavelength.
10.Ultrasound waves are those sound waves
with frequencies less than 20 Hz.