1. Communication Topic 8: Sound
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis

2. 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

3. 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

4. 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

5. 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

6. 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).

7. 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

8. 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

9. 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).

10. 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.

11. 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

12. 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.

13. 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

14. 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.

15. 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.

16. 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

17. 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.

18. 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

19. Activity
-Students to watch Bill Nye Sound Video