Sound WavesSound Waves

Refresh: Types of WavesRefresh: Types of Waves

• Longitudinal or compression – vibrate Longitudinal or compression – vibrate parallel to velocity. ex. Soundparallel to velocity. ex. Sound

• Transverse – vibrations perpendicular Transverse – vibrations perpendicular to velocity. ex. Light and water to velocity. ex. Light and water waveswaves

Soundwave velocitySoundwave velocity

• Air (@ 20Air (@ 2000 C) – 343 m/s C) – 343 m/s

• Water – 1482 m/sWater – 1482 m/s

• Seawater – 1522 m/sSeawater – 1522 m/s

• Steel – 5960 m/s (trains)Steel – 5960 m/s (trains)

– 1 mile = 1600m1 mile = 1600m

Denser = Faster!Denser = Faster!

What type of relationship is

this?Directly

Proportional of course!

Reminder: Reminder: υυ=f=fλλ• The velocity of a wave determines The velocity of a wave determines

other properties as well… f and other properties as well… f and λλ..

• v = ?v = ?

• V determined by mediumV determined by medium

Visualizing Sound wavesVisualizing Sound waves

• Sound waves create rings that move Sound waves create rings that move away from the wave source.away from the wave source.

• Each ring has a Each ring has a λλ

from the next ringfrom the next ring

• λλ is equal to is equal to

all others if the source all others if the source

is stationary.is stationary.

Moving wave sourcesMoving wave sources

• When a wave source moves, the When a wave source moves, the wavelength and frequency becomes wavelength and frequency becomes distorted.distorted.

• λλ becomes a different length becomes a different length depending on the observer’s depending on the observer’s

position.position. υ

Moving wave sources #2Moving wave sources #2• The faster the wave source’s The faster the wave source’s

velocity, the more distorted the velocity, the more distorted the λλ..

Source moving at the speed of the wave

υ

Moving wave sources #3Moving wave sources #3

Low frequency observedHigh frequency observed

λ λ

Doppler Effect – apparent shift in frequency of a

wave caused by a moving wave source.υ

The “Sound Barrier”The “Sound Barrier”

• 11stst broken by Chuck Yeager (US Air broken by Chuck Yeager (US Air Force test pilot) in the Glamorous Force test pilot) in the Glamorous Glennis… a rocket plane named after Glennis… a rocket plane named after his wife.his wife.

The “Sound Barrier”The “Sound Barrier”

• Usually, a “cloud” Usually, a “cloud” forms as water vapor forms as water vapor condenses under the condenses under the extreme pressure.extreme pressure.

υ

• A sonic “BOOM” is an extreme example A sonic “BOOM” is an extreme example of Dopplerof Doppler

• The wave source moves faster than the The wave source moves faster than the wave of sound wave of sound

• A “cone” of compression results as the A “cone” of compression results as the air tries to get out of the way.air tries to get out of the way.

F-14 Tomcat and F-18 Hornet F-14 Tomcat and F-18 Hornet going Supersonic – MACH 1going Supersonic – MACH 1

Video of sonic BOOM!!!Video of sonic BOOM!!!

• 2006-6-5_Sonic_Boom.MPG2006-6-5_Sonic_Boom.MPG

• SupersonicF14_2.mpegSupersonicF14_2.mpeg

InterferenceInterference

• Destructive Destructive

• ConstructiveConstructive

+ =

+ =

Interference#2Interference#2

Resonance – “resound”Resonance – “resound”

•Just like constructive Just like constructive interference, resonance interference, resonance occurs when 2 vibrations occurs when 2 vibrations occur in phase, producing a occur in phase, producing a bigger vibration.bigger vibration.

• http://video.google.com/videosearch?sourchttp://video.google.com/videosearch?sourceid=navclient&hl=en-GB&rlz=1T4GZEZ_eeid=navclient&hl=en-GB&rlz=1T4GZEZ_en-GBUS304US304&q=Tacoma%20Narrowsn-GBUS304US304&q=Tacoma%20Narrows%20Bridge&um=1&ie=UTF-8&sa=N&tab=%20Bridge&um=1&ie=UTF-8&sa=N&tab=wv#wv#

Use of sound technologyUse of sound technology

•Thunder and lightning! 5 sec Thunder and lightning! 5 sec ~ 1 mile.~ 1 mile.

•Sonar – using the echo of a Sonar – using the echo of a soundwave to determine soundwave to determine distance and position of distance and position of objects.objects.

http://earthguide.ucsd.edu/images/aldhttp://earthguide.ucsd.edu/images/aldemo/swf/sonboat.htmlemo/swf/sonboat.html

Echolocation - batsEcholocation - bats

See: Ben Underwood

Refresh: Vibrations Refresh: Vibrations • A “vibration” can be compared to a A “vibration” can be compared to a

pendulum swinging back and forth as its pendulum swinging back and forth as its energy is transformed from KE to PE to KE.energy is transformed from KE to PE to KE.