November 27

• Bell work – What is your spirit animal? • Prepare a new Notes Page: Chapter 16

Section 1

Chapter 16 Section 1 Sound is a Wave

Sound is a mechanical wave

• It transfers energy through matter

1. Can you think of a solid material sound travels

through?

2. Can you think of a liquid sound travels through?

3. Can you think of a gas sound travels through?

Sound is a mechanical wave

• Sound makes particles of matter vibrate

Animation courtesy of Dr. Dan Russell, Grad. Prog. Acoustics, Penn State http://www.acs.psu.edu/drussell/Demos/waves/wavemotion.html

http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-as-a-Longitudinal-Wave

Humans make sound by vibrating Vocal Chords

Humans detect sound when tiny organs in the ear

sense vibrations

By Chittka L, Brockmann [CC BY 2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia Commons

http://www.physicsclassroom.com/mmedia/waves/edl.cfm

Sound is a longitudinal wave

• Particles vibrate in the same direction the sound

wave travels

By Pluke (Own work) [CC0], via Wikimedia Commons

Sound is a longitudinal

wave

• Sounds waves are

patterns of

compressions and

the spaces between

http://www.smackmypitchup.com/smpu/?sec=content&id=72&topid=123

http://www.physicsclassroom.com/Physics-Interactives/Waves-and-Sound/Simple-Wave-Simulator/Simple-Wave-Simulator-Interactive

a vibrating drum is a good example of how these

high vs low pressure patterns are formed

https://res.cloudinary.com/dk-find-out/image/upload/q_80,w_1920,f_auto/How-sounds-are-created-1_su6wfh.jpg

Sound cannot travel without a medium (no sound in

a vacuum or in outer space)

3 minute video about sound in outer space https://www.youtube.com/watch?v=MqF3pPU1Z4U

Famous experiment by Boyle back in

the 1600’s showed there could be no

sound in a vacuum

The Speed of Sound

• Slower than light

https://upload.wikimedia.org/wikipedia/commons/b/bc/KenGriffeyJr2009ST.JPG

The Speed of Sound

• Is not always the same

The Speed of Sound

• Depends on material and temperature

The Speed of Sound – varies with materials

• Faster through liquids than gasses

• Even faster in certain solids

The Speed of Sound – varies with materials

• Faster through liquids than gasses

• Even faster in certain solids

Why? - Sound vibrations travel more easily when

particles are close together!

Medium State Speed of

Sound

Air (20o C ) Gas 769 mi/h

Water (20o C ) Liquid 3130 mi/h

Steel (20o C ) Solid 11,200 mi/h

The Speed of Sound –

varies with temperature

• Faster at higher

temperatures

https://www.nde-ed.org/EducationResources/HighSchool/Sound/tempandspeed.htm

Medium State Speed of

Sound

Air 0 C 741 mi/h

Air 100 C 864 mi/h 17% faster

The Speed of Sound – varies with temperature

• Faster at higher temperatures

Why? – Higher Temperature means more particle

movement

Complete the Vocabulary Worksheet for Chapter 16 Section 1