Sound Waves Photos, sounds, and clipart were obtained from Microsoft’s Office products, unless noted on the slide.

This is Alexander Graham Bell’s sketch of how a telephone works. This sketch came from the Library of Congress “American Memory Project.” www.memory.loc.gov We have requested permission to use several other historical photos. As soon as permissions are granted, I will post them. Loretta 

9/26 p. 24 Sound Waves Intro IQ: a. Waves P and Q have the same __________, but wave P has twice the __________ of wave Q. b. Waves Q and R have the same __________, but wave R has twice the __________ of wave Q. c. Wave __________ shows a steady frequency but changing amplitude. d. Wave __________ shows steady amplitude but a changing frequency.  

9/22 p. 24 Sound Waves Notes IQ: White half sheet

OQ: True or False? Wave frequency and energy are NOT related.

Sound Waves In order for sound to be produced, something (the source) must vibrate. Sound travels in longitudinal or compressional waves. Seeing sound waves 3.9 The student will recognize that sound is a form of energy. [P8C2]

Parts of the longitudinal wave: Compression = Area where the particles are pressed together. Rarefaction = Area where the particles are spread apart. A wavelength is one whole compression and one whole rarefaction. Copy the diagram onto your left page.

Sound wave diagram: (Copy)

How many waves are in the above wave train? What is the wavelength? What is the frequency?

Sound needs a source and a medium

Sound can only travel through a medium A medium can be solid, liquid, or gas. Sound waves travel through all of these. 3.3 The student will describe how waves move at different speeds in different materials. [P8C2]

Sound Waves Speed of sound depends on the density (how close the particles) of the medium. Higher density = higher speed Sound travels fastest in solids, followed by liquids, and slowest in air and gases. Vid 3.3 The student will describe how waves move at different speeds in different materials. [P8C2] In dry air, sound travels at about 340 m/s. In steel, sound travels at about 5960 m/s. In water, sound travels at about 1482 ms/s. Students may need to understand that some media, such as a desktop, contain solids and a lot of air.

Speed of Sound In air = 340 m/s Water = 1480 m/s wood = 3850 m/s steel = 5200 m/s (fastest) Speed of sound increases as the temp. of a medium increases even though density decreases.

Sound travels through a medium. Sound Waves Sound travels through a medium. Sound waves cannot travel without a medium, so no sounds in space. Think: How could you hear a spaceship landing on the moon? 3.3 The student will describe how waves move at different speeds in different materials. [P8C2]

Sound waves are often represented as sine waves: A crest corresponds to a compression and a trough corresponds to a rarefaction in the sound wave.

Waves transfer energy without transferring matter. Frequency= waves/time

The energy moves the eardrum which moves small bones inside your ear. How do you hear sounds? Sound waves enter ear. The energy moves the eardrum which moves small bones inside your ear. The auditory nerve sends a message to your brain. Sound video 3.2 The student will describe how wavelike disturbances spread uniformly away from the source. [P8C2] 3.4 The student will differentiate among reflection, refraction, and absorption of waves. [P8C2]

How do you hear sounds This diagram came from www.nasa.gov 3.2 The student will describe how wavelike disturbances spread uniformly away from the source. [P8C2] 3.4 The student will differentiate among reflection, refraction, and absorption of waves. [P8C2] Help students understand that the sound waves are mechanical energy. Click on arrows to make them move. This diagram came from www.nasa.gov

Amplitude= loudness or volume Amplitude is the distance the particles of a medium move from their rest position. Wave amplitude determines the volume (loud or soft). Sound study jams

A low amplitude wave has a soft volume. A high amplitude wave has a loud volume. 3.1 The student will investigate wavelength, frequency, amplitude, and velocity as properties of waves. [P8C1, P8C2] Amplitude

Loudness of Sound in Decibels Loudness (dbs) Hearing Damage Average Home 40-50 Loud Music 90-100 After long exposure Rock Concert 115-120 Progressive Jet Engine 120-170 Pain Sound Graphing

Sound Frequency Frequency is how many waves go past a point in a given amount of time. Which wave has a higher frequency? Waves More waves are going past here Waves 3.1 The student will investigate wavelength, frequency, amplitude, and velocity as properties of waves. [P8C1, P8C2] than here.

In sound waves, frequency determines the pitch (high or low). Vid Frequency = pitch In sound waves, frequency determines the pitch (high or low). Vid Guitar sound waves

A low frequency is a low pitch. A high frequency is a high pitch. Waves A low frequency is a low pitch. Waves 3.1 The student will investigate wavelength, frequency, amplitude, and velocity as properties of waves. [P8C1, P8C2] Humans can hear 20hz to 20,000hz

Sound study jams.

OQ: What time of the day would sound travel the slowest? Why? Morning Mid-afternoon Evening Midnight Pitch vs. volume

Parts of the longitudinal wave: Compression = Area where the particles are pressed together. Rarefaction = Area where the particles are spread apart. A wavelength is one whole compression and one whole rarefaction.

Sound wave diagram: (Copy)

How many waves are in the above wave train? What is the wavelength? What is the frequency?

How does sound reach us?

9/27 p.26 Sound Wave Phenomena IQ: Draw transverse waves to represent each of the following sounds One that gets louder over time but stays at the same pitch. gets softer and higher pitched. Coolest things sound can do

Sound Wave Phenomena When a sound wave hits a new medium: 1. Some or all of it could be absorbed by soft materials. Absorbed sound energy turns into heat energy. Ex. 3.3 The student will describe how waves move at different speeds in different materials. [P8C2] 3.4 The student will differentiate among reflection, refraction, and absorption of waves. [P8C2] What happens when you yell into a pillow? Anechoic chamber

Sound Possibilities 2. Some or all of it could be reflected off of smooth surfaces. Called an echo. Reverberation: A bunch of echoes. 3.3 The student will describe how waves move at different speeds in different materials. [P8C2] 3.4 The student will differentiate among reflection, refraction, and absorption of waves. [P8C2]

Echolocation (Video) Used by bats, dolphins, and other animals to find prey in the dark or underwater. Bats send out high freq./pitch sounds which get reflected off of objects. Bats can tell the location, distance, size and shape of the objects from listening to the echo. 3.1 The student will investigate wavelength, frequency, amplitude, and velocity as properties of waves. [P8C1, P8C2] 3.2 The student will describe how wavelike disturbances spread uniformly away from the source. [P8C2] 3.4 The student will differentiate among reflection, refraction, and absorption of waves. [P8C2] Use the reading about echolocation in Chapter 3 of their textbook. Echolocation in dolphins: http://www.inkokomo.com/dolphin/echolocation.html All kinds of info about bats: http://www.batbox.org/ Echolocation in various marine animals: http://oceanlink.island.net/oinfo/acoustics/echolocate.html

Sound Possibilities 3. Some or all of it could be refracted or bent. Ex. when sound enters water from air. Video Due to changing density of mediums. 3.3 The student will describe how waves move at different speeds in different materials. [P8C2] 3.4 The student will differentiate among reflection, refraction, and absorption of waves. [P8C2]

4. Sound can diffract or bend around a corner or a barrier. Ex 4. Sound can diffract or bend around a corner or a barrier. Ex. we can hear sounds from down the hall and other classrooms.

Longer wavelengths diffract better and travel farther.

Think Which type of thunder can we hear from a distance? (Cracking or rolling) Why do you think that is?

OQ: Which of the phenomena mentioned below occurs less in this classroom vs. your English classroom? Why? Reflection Absorption Refraction Diffraction

9/28 p. 28 Doppler Effect IQ: Which sound phenomena are occurring in the picture below (look on previous page for answer choices) Coolest things sound can do

Doppler effect of sound

Due to the motion of either the sound source or the observer. Doppler Effect The pitch of an approaching siren is higher than one moving away from the listener because the waves in the front are closer together (higher frequency) than the ones in the back. Due to the motion of either the sound source or the observer.

Doppler effect (animation 1:01) Doppler effect (Big Bang theory) Change in frequency and pitch of a sound. Listen!

Hears high pitch Hears low pitch

Interesting fact On October 15, 1997 the British built "Thrust SSC" vehicle became the first land based vehicle to break the sound barrier. To be official it had to break the sound barrier twice within one hour. It did this, with an average top speed on the two runs of Mach 1.020. The runs took place in early in the day so that the temperature of the air (and the speed of sound) would be lower. As an interesting side note, this record was set one day after the 50th anniversary of the first supersonic flight made by Chuck Yeager on October 14, 1947 in the "Bell X-1."

Resonance A standing wave occurs when there is constructive and destructive interference between a wave and its reflection. A portion of a wave is at rest and another portion has a large amplitude because of constructive interference. http://physics.info/waves-standing/# A resonant frequency is a frequency at which an object vibrates at maximum amplitude and forms a standing wave.

Resonance Resonance: When an object is vibrating at the same frequency as the resonant/natural frequency of another object, the second object starts to vibrate. Ex. Shaking windows when an airplane flies overhead, when a car shakes from the sound of a stereo. http://home.messiah.edu/~barrett/mpg/mpg.html