Essential QuestionEssential Question

Why/how does the sound from a passing car Why/how does the sound from a passing car change?change?

http://www.kettering.edu/~drussell/Demos/doppler/doppler.html

http://www.kettering.edu/~drussell/Demos/doppler/doppler.html

Stationary Source and Stationary Observers

http://www.kettering.edu/~drussell/Demos/doppler/doppler.html

Stationary Source but Moving Observer

http://www.kettering.edu/~drussell/Demos/doppler/doppler.html

Moving Source but Stationary Observer

RaceRaceCarCar

Car Car PassingPassing

Doppler Effect

Moving Source but Stationary Observer

TrainTrainPassingPassing

DOPPLER (Δvelocity effect)

• A stationary sound source is emitting a 550 Hz buzz. You ride your bike toward the sound at 5 m/s… what do you hear?

DOPPLER (Δwavelength effect)

• You are standing on the side of the road as a police car approaches… it is traveling at 20 m/s and actually producing a 600 Hz siren… What do you hear?

http://kfty.com/weather/interactive/

Doppler RadarDoppler Radar

Another example of using the Doppler EffectAnother example of using the Doppler Effect

Sound…Sound…

Moving source causes a change in Moving source causes a change in frequency for stationary observers.frequency for stationary observers.

What else might the Doppler Effect affect?What else might the Doppler Effect affect?

http://www.kettering.edu/~drussell/Demos/doppler/doppler.html

Source Moving as fast as the waves it is making.

Object traveling FASTER thanObject traveling FASTER thanthe waves it is making.the waves it is making.

http://www.kettering.edu/~drussell/Demos/doppler/doppler.html

Source Moving FASTER than the waves it is making.

Source Moving FASTER than the waves it is making.

CrestCrestCrest Crest CrestCrest

+ Crest + Crest

Big fatty Big fatty CrestCrest

The Learning Channel – “Extreme Machines”

October 14 1947

Chuck Yeager – October 14, 1947Chuck Yeager – October 14, 1947

Source Moving FASTER than the waves it is making.

CrestCrestCrest Crest CrestCrest

+ Crest + Crest

Big fatty Big fatty CrestCrest

http://www.kettering.edu/~drussell/Demos/doppler/doppler.html

2193.16 miles per hour2193.16 miles per hour

http://www.mediacen.navy.mil/pubs/allhands/jan01/f14tomcat.jpg

http://www.ctrl-c.liu.se/ftp/images/AVIATION/MILITARY/USA/f14/f14-3.jpg

F-14F-14TomcatTomcat

dB – Decibels… better thought of as deci - BellsdB – Decibels… better thought of as deci - Bells

Loudness of SoundLoudness of SoundJet Engine at 30 m

Threshold of Pain,Siren, Loud Rock Concert

Lawn Mower

Vacuum Cleaner

Normal Conversation

Mosquito Buzzing

Whisper

Rustling Leaves,Normal Breathing

Threshold of hearing

140 dB

120 dB

100 dB

70 dB

50 dB

40 dB

20 dB

10 dB

0

0 dB to 10 dB0 dB to 10 dB

= 10 times louder= 10 times louder

= 10= 1011

10 dB to 20 dB10 dB to 20 dB = 10= 1011

= 10 times louder= 10 times louder

20 dB to 40 dB20 dB to 40 dB = 10*10 or 10= 10*10 or 1022

= 100 times louder= 100 times louder

40 dB to 70 dB40 dB to 70 dB = 10*10*10 or 10= 10*10*10 or 1033

= 1000 times louder= 1000 times louder

70 dB to 120 dB70 dB to 120 dB = 10= 1055

= 100,000 x louder= 100,000 x louder

15.2 dB to 48.4 dB15.2 dB to 48.4 dB

= 10= 103.323.32

= 2,089 x louder= 2,089 x louder

= 48.4 – 15.2 = 33.2= 48.4 – 15.2 = 33.2