Sound

Warm-Up What do waves carry? What are the two different types of waves? What are the different types of wave behavior?

Josh was in the room he shared with his two brothers Josh was in the room he shared with his two brothers. His brothers were in the other room watching TV, and Tony had taken advantage of this opportunity to crank up his favorite song on his iHome. He worked on his science homework as he bobbed his head to the music. Then his mom stuck her head in the door. “Josh!” she said. “Turn off that noise!” Josh was offended. “It’s not noise, Mom, it’s music,” he said. “That racket?” said Josh’s mom. “What’s musical about that?” Josh wasn’t sure what to say. “Um, lots of things,” he said. “Well,” his mom said, “the day you can prove to me that that cacophony is music, I’ll let you play it all you want. Until then, turn it off.” My mom, Josh thought, has underestimated this artist – AND me. I’ll prove to her that this is music, and then she won’t be able to say anything to me about it. Josh is fooling around on his friend Chris’s computer, downloading MP3s, when he notices that there is an oscilloscope on Chris’s music player. As music plays on Chris’s computer, the sound waves appear onscreen. “This is the perfect way to prove to my mom that this is music,” Josh thinks.

Inquiry Demo Domino Effect Which row will win? Why? What happened?

Remember… Mechanical waves require a medium A medium is matter that a wave can travel through Sound waves are an example of mechanical waves All waves have frequency, speed (velocity), amplitude, and wavelength

Characteristics of sound waves Sound waves are longitudinal waves Made up of areas of high pressure and areas of low pressure Sound cannot move in a vacuum Why not?

Characteristics of sound waves Velocity of a sound wave depends on temperature Wavelength of a sound wave is the distance between areas of maximum pressure

Sound wave interactions Reflected sound waves are called echoes The harder and smother the surface, the stronger the reflection Sound waves also diffract

Speed of Sound Depends on the medium’s… Elasticity: ability for a material to bounce back after being disturbed Temperature: the average kinetic energy of a substance Density: the amount of matter in a given space (mass/volume) Denser medium = more mass The waves travel the fastest in solids, and increasingly slower in liquids, and slowest through gases.

Interpret the graph and chart. When is sound traveling the fastest?

Breaking the Sound Barrier Sound travels slower at lower temperatures http://www.youtube.com/watch?v=ogtjBcIjrjc

Which substance do sound waves travel the fastest through? A pool of water A pool of jello An empty pool Explain why? What if we had 3 pools of water at 75 degrees Celsius, 32 degrees Celsius, and 100 degrees Celsius? Why?

Playing Instruments How do you play different notes? How do you know you are hearing different notes? What makes music, music and not just noise?

Frequency The frequency of the sound wave is the number of oscillations in pressure each second. Oscillations

You’re too Pitchy Pitch: how high or low a sound seems to a listener Depends on the frequency of the sound wave High frequency = high pitch Low frequency = low pitch Frequency is measured in units of Hertz Helium voices http://www.youtube.com/watch?v=d-XbjFn3aqE What is the difference in regards to frequency of the high and lower octaves of notes?

Playing Instruments Length effects frequency High wavelength = low frequency & note Low wavelength = high frequency & note https://www.youtube.com/watch?v=ymCa87hYIUE

Music Music is a combination or sequences of sounds that people enjoy listening to. Musical instruments make different sounds by plucking the strings. The shorter the string, the quicker it vibrates producing a high sound. The longer the string, the slower it vibrates producing a low sound.

Quick Check The instrument shown above is called a harp. Which string would you play if you wanted to play a high-pitched note? Why?

It all Started with a Big Bang https://www.youtube.com/watch?v=Tn35SB1 _NYI

Doppler Effect Change in frequency due to the relative motion of source and detector Changes because the motion of the source adds to the motion of the waves Frequency is higher when moving toward you, lower when moving away. How does a bat use the Doppler Effect to hunt?

Doppler Effect

Loudness Your perception of the amount of energy in a sound The amount depends on the energy used and the distance from the source of the sound Amplitude of the wave shows loudness Larger amplitude = louder sound

Loudness The greater the energy used the louder the sound Intensity: the amount of energy a sound wave carries per second Shorter distance = decreased intensity Loudness is measured in the unit Decibels (dB)

How does the ear work? Sound waves are sent. The outer ear “catches the sound waves”. The middle ear takes the sound waves and “vibrates” the eardrum. The inner ear sends the messages to the brain. Middle Ear Outer Ear Sound Waves Inner Ear The brain puts it together and hooray! You hear your favorite song on the radio.

How You Make Sounds We use our vocal cords to make sounds in our throat. When we speak, our vocal cords vibrate. Place your hand on your throat when you talk, and you can feel the vocal cords vibrate.

Audiologist An audiologist is a person who tests people’s hearing. They use special machines that make sounds. They also help people who do not hear well. Have you had your hearing tested?

Practice Answer the questions on 545 and 551 in your textbook.

Close A student is practicing her instrument. She does not want anyone to hear her so she wants to practice in a location that in which the sound waves will not travel quickly. She has found four rooms. They have walls with insulation of brick, warmer air pockets, cooler, air pockets, and a liquid gel like substance. Which room should she pick? She wants to hit the highest pitch possible. How should her sound waves look?

A student running by hears her playing because she left the door open A student running by hears her playing because she left the door open. It is increasingly loud as he nears and fades away as he passes by. What is happening to the sound waves and what is this process called?