3.4 Sound

Describe the production of sound by vibrating sources
Describe the longitudinal nature of sound waves
Sound energy is produced when an object vibrates. The sound waves travels through medium such as air, water, wood or metal, by vibrations particles. Sound is propagated by means of longitudinal waves.

Supplement
Describe compression and rarefaction
LONGITUDINAL WAVE: Wave where the oscillation is parallel to the direction in which the energy travels.
Long_wave.gif
Animation courtesy of Dr. Dan Russell, Kettering University
Compressions: The most dense part of a longitudinal wave.
Rarefactions: The least dense part of a longitudinal wave.

Transmission of sound from youtube.com Published on 20 Jun 2012 by Designmate Pvt. Ltd. - Official

Relate the loudness and pitch of sound waves to amplitude and frequency
For a wave:
  • the amplitude is the maximum height of the wave from its resting position – the greater the amplitude, the louder the sound
  • the wavelength is the distance between the crests (tops) of two waves next to each other (or any other two identical point on waves next to each other)
  • the frequency is the number of waves per second – the higher the frequency, the closer together the waves are and the higher the pitch

Loudness and pitch of sound waves from BBC Bitesize

State the order of magnitude of the speed of sound in air, liquids and solids
State typical values of the speed of sound in gases, liquids and solids
Speed of sound.JPG
Speed of sound in different material from vernonschools.org

In general, sound travels slowest in gases, faster in liquids, and fastest in solids.
Sound travels more than four times faster in water and more than seventeen times faster in steel than it does in air.


State the approximate range of audible frequencies for a healthy human ear is 20 Hz to 20,000 Hz.
Online Tone Generator from www.szynalski.com
Human audible range of frequencies 20Hz ~ 20,000Hz

Show an understanding of the term ultrasound
Ultrasound is sound wave that is above the range of human hearing.

High-frequency sound waves are used to picture organs and structures inside a body. Medical doctors use it to image the heart, blood vessels, kidneys, liver, and other organs. During pregnancy, doctors use ultrasound to view the fetus. Unlike x-rays, ultrasound does not expose you to radiation.

More information on general ultra sound imaging from www.radiologyinfo.org

Show an understanding that a medium is needed to transmit sound waves


Bell in a vacuum jar from youtube.com
Can you hear the Sun?

Describe an experiment to determine the speed of sound in air
Clap-echo method from BBC Bitesize
This method involves measuring the time taken for you to hear an echo from a sharp clap. You stand a long distance from a wall, clap, and listen for the echo. The distance travelled is twice the distance from you to the wall (because the sound has to travel to the wall and back).

Describe how the reflection of sound may produce an echo

When sound hits on a surface, it is partly reflected and partly absorbed. Wood, carpets, curtains, clothes absorb sound and walls of a room are good reflectors of sound. An example of the reflection of sound is echo. It is the bounce off of a sound wave as it hits a barrier. An application of sound reflection is echo sounding that is used by scientist to map the sea floor and to determine the depth of the ocean.
Echo sounding.JPG
Echo sounding from www.divediscover.whoi.edu