Communication
Topic 8: Sound
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis
DOT Point(s)
 explain why sound is a useful and versatile form of
communication
 explain that sound is produced by vibrating objects and that the
frequency of the sound is the same as the frequency of the
vibration of the source of the sound
Introduction
Sound is another very
important form of
communication to humans.
Sound is a form of energy that
requires a medium for
propagation. In this section, we
are going to explore how sound
is used in communication.
o5.com
Introduction
‘If a tree falls in the forest and there
is no one there to hear it, will there
be a sound?’
Eighteenth century thinkers
pondered over this question just as it
puzzles us today. We now consider
sound to be a combination of
physical vibrations causing
movement of molecules and a
physiological sensation recorded in
the animals brain. So if there’s no
animal to hear the tree fall, would
there be the noise???
forestry.about.com
Introduction
Sound is a form of energy that
requires a medium for
propagation. The material
through which the energy of a
sound wave travels is called the
medium. Media may be solid,
liquid or gas but must contain
particles that are able to be
dispersed and then return to
their original position (elastic).
mohinishshende.blogspot.com
Introduction
In 1660 Robert Boyle
performed a simple sound
investigation. He hung a ‘watch
with a good alarm’ from a
thread into a glass jar. He then
pumped the air from the jar
(creating a vacuum).
www.glogster.com
Introduction
‘We silently expected the time
when the alarm should begin to
ring… And were satisfied that
we hear the watch not at all.
Wherefore ordering some air to
be let in, we did by help of
attention, begin to hear the
alarm’ (Stevens and Warshofsky,
1980).
unitednuclear.com
Introduction
Boyle showed that sound does not travel in a vacuum. Sound
requires a medium for propagation and transmission. Sound
cannot be transmitted through a vacuum as there are no particles
to produce a wave.
commons.wikimedia.org
Sound
 Sound originates when something vibrates rapidly enough to
organise the movement of molecules, so as to send a
compression wave through a medium.
The wave can only travel through media which contain particles
that can be compressed (compression) and spread (rarefaction).
www.cartage.org.lb
Sound
 The particles move backwards and forwards in the same
direction as the flow of energy.
It is the energy that is transferred, not the molecules which make
up the medium. Waves can be measured in terms of their
frequency, wavelength and amplitude.
www.mediacollege.com
Sound
Frequency
The frequency of vibrations is the
number of waves which pass a
given point in one second. One
cycle per second is called hertz
(Hz). The frequency of the sound
is the same as the frequency of the
vibration of the source of the
sound
www.webtech.buffalo.edu
Sound
Pitch
Frequency determines the pitch of a sound. Higher-frequency
vibrations results in high-pitched sounds and, correspondingly,
low frequency vibrations give low pitched sounds.
www.ducksters.com
Sound
Wavelength
The wavelength of a sound wave is the distance between the
centres of two adjacent compressions or rarefactions. Low
frequency sounds have long wavelengths while high frequency
sounds have short wavelengths.
science.hq.nasa.gov
Sound
Amplitude
The amplitude of a sound wave is the maximum distance that a
particle moves away from its original position. The amplitude
determines the volume of the sound.
www.bbc.co.uk
Sound as Communication
 Sound bends around objects and
travels around corners. It travels
through all substances, solids,
liquids and gases.
Whatever habitat, an animal is
always surrounded by a sound
transmitting medium. An animals
reliance on sound, not only for
communication but also for
overlapping functions of navigation
and hunting, is therefore always
supported by its environment.
www.innertranquillity.com.au
Sound as Communication
 Animals do not have to be in
visual or direct contact to
communicate using sound.
When visual (sight), tactile
(touch) and olfactory (smell)
senses are impaired or absent,
sound can be used as the
primary method of
communication.
users.mcmedia.com.au
Sound as Communication
 A variety of sounds may be produced by varying the pitch,
loudness and tone.
 A complete message can be conveyed in a short space of time.
 Sound particularly low-frequency sound, will travel long
distances.
www.nature.com
Sound as Communication
Toothed whales use sound in a similar way to bats. They emit
sounds and then listen for the echo to come back to them. This
type of SONAR (SOund NAvigation Ranging) works well in
complete darkness. Its referred to as echolocation.
fantasticaanimal.blogspot.com
Activity
-Students to watch Bill Nye Sound Video