Chapter 15 Chapter 16 Waves and Sound

Sound Activities Lab Station #1: Drum with paper clips on the top. (This can be made with wrapping paper over a coffee can if you don't have a real drum available.) Students should tap on the drum and observe what happens to the paper clips. - Students should tap on the drum. What do you see? What do you hear?   Lab Station #2: Touch side of your throat and say ahh. - What do you feel as you say ahh? What do you hear? Lab Station #3: Rubber band strung between two pegs or nails. - Pluck the rubber band. What do you see? What do you hear? Lab Station #4: Tuning fork in water. - Gently strike the tuning fork on the pad and then place it in the water. Describe what you observe. What do you see? What do you hear? Lab Station #5: Strike the tuning fork(s) with the rubber mallet and bring it close to the ear. Do one fork at a time. Do NOT bang the forks with or on anything else. - What do you hear? What do you see? Lab Station #6: Steel yardstick or ruler on edge of a table. Hold one end of the ruler firmly against the top of the table. Snap the other end. What do you see? What do you hear? Lab Station #7: The Thunder Tube. Hold the Thunder tube steady and gently shake it. What do you hear? Explain why. Lab Station #8: The Sound Whistles. Hold the non flared end of the tube with one hand. With plenty of room swing tube around and around. What do you hear? Why?

What is a wave? A repeating disturbance /movement that transfers energy through matter or space.

Waves transfer energy not matter. Waves exist if they have energy to carry. Vibration is transferred from particle to particle ……..

Types of waves: Waves are classified according to how they move.

Types of Waves Mechanical waves Require a medium to carry the energy. ***Waves such as light, x-rays, and other forms of radiation do not require a medium*** - not mechanical.

A)Transverse Waves Matter in the wave moves up and down at a right angle to the direction of the wave

What are the parts of a wave? Transverse wave The crest is highest point The trough is lowest point. The rest position is called the node. The wavelength is the distance from one point on the wave to the next corresponding adjacent point. amplitude – height of wave Period 8 needs to start here on 3/18

It is directly related to the amount of energy in a wave.

B) Longitudinal Waves (Compression Waves) Matter in the wave moves back and forth parallel to the direction of the wave. Ex: Sound

Parts of a Compressional or Longitudinal wave The area squeezed together is the compression. The area spread out is the rarefaction. Wavelength : The distance from the center of one compression to the center of the next compression.

Amplitude = Density Which Spring has more energy?

Longitudinal or Transverse?

Example of a transverse wave:

What is wavelength? What is wave frequency? Wavelength measures distance. Use distance units What is wave frequency? Frequency measures the number of waves that pass through a point in one second. Unit for frequency - # waves per second (Hertz - Hz). One Hz = One wave per second.

1 cycle = 1 full wave to repeat itself

3 cycles 2 4 5 6 7 8 9 10 11 12 1 3 Time in seconds

from 0 to 12 seconds 2 4 5 6 7 8 9 10 11 12 1 3 Time in seconds

f=3 /12 s = ¼ Hz 2 4 5 6 7 8 9 10 11 12 1 3 Time in seconds

1 cycle in 4 seconds= ¼ Hz 2 4 5 6 7 8 9 10 11 12 1 3 Time in seconds

Wavelength and frequency are inversely related. What is the Frequency?? 12 Hz 6 Hz Wavelength and frequency are inversely related.

How is Wave Speed calculated? A wave moving through a medium travels at a certain speed. This is Wave Speed. How is Wave Speed calculated? Wavelength is represented by Greek letter lambda (λ) and frequency is represented by (f)

A wave has a wavelength of 15 cm and has a frequency of 10 waves/second. What is the speed of the wave? (λ) = 15 cm f = 10 waves/second V = ? V = .15m x 10 hz = 1.5 m/s The speed of a wave on a rope is 50cm/s and it’s wavelength is 10cm. What is it’s frequency? V = 50cm/s (λ) = 10 cm f = ? f = V / (λ) =5 Hz

Can you draw a wave?

DO NOW: Wave Velocity A wave at the ocean has a wavelength of 5 meters. The frequency of the wave is .75 kilohertz. What is the velocity of the wave? V= ? f = .75 kHz (λ) = 5 m V = (λ) x f .75kHz x 5m = (750 Hz x 5m) = 3,750m/s or 3.75 km/s

Slinky Lab- Teams of 3 – 1 timer, 2 wave makers Read lab procedure before doing anything!!!! It can be tricky!! Complete data table as presented.

Section 15.3 – Interactions of Waves (5) REFLECTION When energy hits a surface through which it can not pass – it “bounces”. A sound wave reflection = “an Echo” Smooth hard surfaces reflect best. Rough soft surfaces reflect poorly. Energy can also be absorbed or transmitted.

2) Refraction When a wave enters a new medium at an angle, one side bends before the other. One side changes speed before the other.

Like light, sound can be… Reflected – sound reflections are called echoes. “Sounds Bounce” Refracted –why you might sound strange if you try talking underwater... “Sounds Bend”

3) Diffraction : When an object causes a wave to change direction and bend around it.

4) Wave Interference: When 2 waves collide “in phase”

When 2 waves collide “out of phase

Chapter 16 - What is Sound? Sound (compressional wave) travels through the air through a series of compressions and rarefactions.

Sound can travel through different media. We hear sound usually through air. 1) The denser the medium, the faster sound will travel. Why? 2)The higher the temperature, the faster sound travels. Why?

Speed of Sound Using the information given: Why do you think there is a difference? List all possibilities. Air 20oC 343 m/s 0oC 332 m/s Water Salt Fresh 1482 m/s 1500 m/s 1435 m/s Steel 5100 m/s

What is Sound Intensity? Sound Intensity = Energy of the sound wave. The greater the intensity the farther the sound will travel and the louder the sound will appear. “Loudness” is human perception of sound intensity. Unit for loudness is decibels.(dB)

Loudness in Decibels Normal Conversation – 60 Fire Alarm - ( No less than 70 – no greater than 120) Shot Gun Blast- 170

How is frequency related to pitch? Pitch of a sound wave is directly related to frequency. A high-pitched sound = high frequency A low-pitched sound = low frequency

What is the Doppler Effect? The Doppler Effect is the apparent change in frequency detected when the sound is moving relative to the person hearing the sound. http://www.youtube.com/watch?v=gzUhw1rRJtc

Doppler Effect Video-Excellent example of Doppler Effect with car horn (26 seconds )

Speed of Sound Lab How fast does Sound travel? Effect of Temperature? Wind? Calculate speed of sound

Period Temp (o C) Other Conditions (Wind, noise, etc..) Humidity Levels Average Class Speed 4 8 am 46 F 8 C Lawn mower Birds No wind 87% 277.68 m/s 2 10 am 54 F 16 C Wind 5mph Airplanes, Lawn mowers, trucks 64% 229.53 m/s 5 12 pm 65 F 19 C Wind 5 mph Airplane, lunch time kids 41% 227.91m/s 6 1 pm 68F 20 C Wind NW 9 mph Airplane, lawn mower, chain saw 30% 241.62 m/s 7 2 pm 72 F 22C Wind SSW 5 mph 32% 236.91 m/s http://www.youtube.com/watch?v=pjP7hmBfYdA

Human Range A healthy human ear can hear frequencies in the range of 20 Hz to 20,000 Hz. Humans cannot hear below 20 Hz. Sounds below 20 Hz - Infrasonic Sounds above 20,000 HZ- Ultrasonic

Hearing problems Our hearing range can be damaged by several things: Too much ear wax! Damage to the auditory nerve Illness or infections Old age (sort of like Mrs. Hyland)

Around 80% of deafness is due to damage to the cochlea cells. Deafness is one of the most common disabilities.

Ultrasonic Sounds above 20,000 Hz . Some animals can hear frequencies in this range - (humans cannot). Ex: Sonar, Medical uses

Sonar – A system that uses the reflection of underwater sound waves to detect objects. Can determine distance.

Clicking noises ECHOLOCATION: High Frequency sounds that are emitted by certain animals to locate prey. Sound waves bounce off and return to the animal (echoes) allowing the hunter to pinpoint location of prey. Ultrasonic cries http://www.youtube.com/watch?v=XUXh-X1iveU

Infrasonic sounds http://wn.com/infrasonic#/videos http://www.youtube.com/watch?v=pLBe8sOPO7Y http://wn.com/infrasonic#/videos http://www.youtube.com/watch?v=fwrbFj9r10Y

http://www.youtube.com/watch?v=gzUhw1rRJtc http://www.youtube.com/watch?v=WuaEFR3wGQE

Wave Reflection – Do Now Acoustics of room design: You need some reflections to “liven” the room. Too many reflections and the sound gets mushy. Think about a concert hall or auditorium and come up with some different sound treatments used. What are some examples?

Whale strandings – Why do they do it? A change in the behavior of dolphins has biologists concerned that use of low frequency sonar could be disorientating whales and dolphins. Using what you know about sound waves and sonar, explain what is happening to the animals.