The Sound Unit

Sound energy needs a medium to travel through.

Solids, liquids, and gases conduct sound.

Sound will not travel in a vacuum, a space with no

matter.

Sound is a form of energy that travels in waves.

All sounds are created by vibrations.

Vibrations cause a movement of air molecules called a sound

wave.

Sound waves travel as longitudinal waves with areas of compression (tightly packed air molecules)

and areas of rarefaction (air molecules spread apart).

compression rarefaction

The crests of these waves are areas of high density, called compressions. The troughs are called rarefactions.

Sometimes sound waves are shown as a transverse wave. Light and heat are actually transverse waves, not sound. We use the transverse wave because it is easy to study. crest

trough

amplitude

wavelength

Wavelength - the distance between two waves Crest - the top of a wave

Trough - the bottom of a wave

Amplitude - the height of a wave, a measurement of the amount of energy the wave is carrying. (loudness)

C

T

W A

Frequency - Vibrations or waves / second, measured in hertz

Pitch - How high or how low a sound is

transverse

longitudinal

transverse

longitudinal

A B

D C

Compare Waves 1. Which wave has a low frequency and low

amplitude?, high frequency, high amplitude?

2. Which wave has a steady amplitude but changing frequency?, steady frequency but changing amplitude?

Liquids transmit sound faster than gases. Sound travels 4-5 times faster in

water than in air.

Sound travels 15 times faster

through steel than air. Why??

760 miles/hour

1mile in 5 seconds

The Speed of Sound

Air @ 70 degrees F 340 m/s

Air @ 30 degrees F 300 m/s

H2O 1500 m/s

Brick 3700 m/s

Steel 5200 m/s

SPEED OF LIGHT

300,000,000 Meters /second (remember sound? 340 meter/sec.)

Light can travel 7 times around the world in 1 second. WOW!

This is about 180,000 miles per second.

neeerrrrrrooooooooooooooooooommmm

Doppler Effect - The apparent change in the pitch of a sound created by a moving object.

Breaking the Sound Barrier

An aircraft traveling at close to the speed of sound catches up to its own sound waves. These waves form a wall of compressed air called the sound barrier.

A sonic boom is created by any craft that travels faster than the speed of sound. The loud crack is created by super compressed air.

Human Hearing Range 20 – 20,000 Hz Infrasound is any sound below our hearing range

Ultrasound is any sound above our hearing range

http://www.phys.unsw.edu.au/jw/hearing.html

http://www.ltscotland.org.uk/5to14/resources/science/oscilloscope.asp

ULTRASOUND High frequency waves are used to show images inside patients.

This could be your first baby photo.

Today’s ultrasound is high definition.

Ultrasound is used for:

•  Diagnosis of an injury.

• Treatment for pulled ligaments and muscles.

More uses for Ultrasound:

Illness or pregnancy of a Horse

Research about Turtles

Animals benefit too - it’s painless.

Echo - A reflected sound wave.

Echolocation - Animals that use reflected sound waves to search for prey or to find their location.

Echolocation:

In the air

and water.

Sonar -Sound Navigation and Ranging Electronically produced ultrasonic

waves are sent out and reflected off of objects below. The reflected waves provide an image of underwater objects.

Work slide

SONAR - used to locate sunken ships

FISH FINDERS AND ECHO SOUNDERS

different shapes and sizes

Resonance – Vibrations traveling through a material match that materials natural frequency.

Decibel level of common sounds

Decibel – The unit used to measure sound loudness.

Noise – any unpleasant or unwanted sound, usually with an irregular wave pattern.

A

B

Engineered Solutions to Controlling Noise Pollution:

Acoustics

How do we hear these vibrations called sound?

Outer Ear-Pinna

The Ear

Outer Ear

Pinna - Collects sounds waves and funnels them inward.

Auditory Canal - Lined with tiny hairs, the auditory canal filters out unwanted particles. Ear wax helps with this process. Also, the canal provides a passageway for sound to take.

Middle Ear Ear Drum (tympanic membrane) - As sound waves hit the ear drum they are turned back into vibrations.

Healthy

Infected

Perforated

Tubes

3 Bones (Malleus Incus Stapes) - These bones pass vibrations from the

eardrum to the inner ear.

Inner Ear Cochlea - This snail shaped organ is filled with fluid and lined with hair. It turns vibrations into electrical messages.

Neurobiology of the Cochlea

http://www.blackwellpublishing.com/matthews/ear.html

http://www.hhmi.org/biointeractive/media/cochlea-lg.mov

Semicircular Canals – the fluid inside of these organs moves and sends messages to your brain to help you keep your balance.

Work slide

Relative loudness of common sounds