Unit 2 Lesson 1 Sound Waves and Hearing Copyright © Houghton Mifflin Harcourt Publishing Company

Listen Up! Copyright © Houghton Mifflin Harcourt Publishing Company What is sound? A vibration is the complete back and forth motion of an object. Beating a drum causes the drum skin to vibrate, which causes the air around it to vibrate. Unit 2 Lesson 1 Sound Waves and Hearing

Copyright © Houghton Mifflin Harcourt Publishing Company What are sound waves? A sound wave is a longitudinal wave that is caused by vibrations and that travels through a medium. In a longitudinal wave, the particles of a medium vibrate in the same direction that the wave travels. As the wave passes through a medium, its particles compress together and then spread out. Unit 2 Lesson 1 Sound Waves and Hearing

How do sound waves travel? Sound waves travel in all directions away from their source. They can only travel through a medium. All matter—solids, liquids, and gases—is composed of particles. The particles in matter make up the medium through which waves can travel. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 1 Sound Waves and Hearing

How do sound waves travel? The particles of a medium only vibrate back and forth along the path of the sound waves. Most sounds travel through air, but some travel through other materials, such as water, glass, and metal. In a vacuum (like space) there are no particles to vibrate, so no sound can be made. Sound must travel through a medium to be detected. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 1 Sound Waves and Hearing

Do You Hear That? Copyright © Houghton Mifflin Harcourt Publishing Company How do humans hear sound? Humans detect sounds with their ears, which act like funnels for sound waves. The ear directs sound vibrations from the environment to the three tiny bones in the middle ear. These bones carry vibrations from the eardrum to the oval window (3 tiny bones), which leads to the inner ear. Unit 2 Lesson 1 Sound Waves and Hearing

Copyright © Houghton Mifflin Harcourt Publishing Company How do humans hear sound? Vibrations travel through fluid to the cochlea, which has thousands of nerve cells. Each nerve cell has tiny surface hairs(cilia) that bend with the vibrations to send electrical signals to the brain, which interprets the signals as sound. Unit 2 Lesson 1 Sound Waves and Hearing

Copyright © Houghton Mifflin Harcourt Publishing Company How do humans hear sound? Describe how sound gets interpreted by the brain. Unit 2 Lesson 1 Sound Waves and Hearing

Can You Hear Me Now? Copyright © Houghton Mifflin Harcourt Publishing Company What determines pitch? Unit 2 Lesson 1 Sound Waves and Hearing Pitch is how high or low you think is a sound is. The pitch heard depends on the ear’s sensitivity to pitches over a wide range. Frequency is expressed in hertz (Hz). One hertz is one complete wavelength, or cycle, per second.

Copyright © Houghton Mifflin Harcourt Publishing Company What determines pitch? Unit 2 Lesson 1 Sound Waves and Hearing In a given medium, the higher the frequency of a wave, the shorter its wavelength and the higher its pitch. High-frequency waves have shorter wavelengths and produce high-pitched sounds. Low-frequency waves have longer wavelengths and produce low-pitched sounds.

What makes a sound loud? Loudness is a measure of how well a sound can be heard. The measure of how much energy a sound wave carries is the wave’s intensity, or amplitude. The amplitude of a sound wave is the maximum distance that the particles of a wave vibrate from their rest position. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 1 Sound Waves and Hearing

What makes a sound loud? The greater the amplitude, the louder the sound. The smaller the amplitude, the softer the sound. Amplifiers can increase loudness by receiving sound signals and increasing the wave’s amplitude. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 1 Sound Waves and Hearing

Turn That Down! Copyright © Houghton Mifflin Harcourt Publishing Company How is loudness measured? Unit 2 Lesson 1 Sound Waves and Hearing Loudness is a characteristic of sound that can be calculated from the intensity of a sound wave. The most common unit used to express loudness is the decibel (dB). One decibel is one tenth of a bel, the base unit. The bel is named after Alexander Graham Bell, who invented the telephone.

Copyright © Houghton Mifflin Harcourt Publishing Company How is loudness measured? Unit 2 Lesson 1 Sound Waves and Hearing The softest sounds most humans can hear are at a level of 0 dB. Sounds that are 120 dB or higher can be painful. Rock concerts usually measure about 115 dB.

Copyright © Houghton Mifflin Harcourt Publishing Company How is loudness measured? Unit 2 Lesson 1 Sound Waves and Hearing Amplifiers can increase loudness by receiving sound signals and increasing the wave’s amplitude.

Copyright © Houghton Mifflin Harcourt Publishing Company How loud is too loud? Unit 2 Lesson 1 Sound Waves and Hearing Short exposures to sounds that are loud enough to be painful can cause hearing loss. Even loud sounds that are not painful can damage your hearing if exposed to them for long periods of time. Loud sounds can damage the hairs on the nerve cells in the cochlea. Once damaged, these hairs do not grow back.

Copyright © Houghton Mifflin Harcourt Publishing Company How loud is too loud? Unit 2 Lesson 1 Sound Waves and Hearing Using earplugs to block loud sounds, lowering the volume when using earbuds, and moving away from a loud speaker are all ways to protect yourself from hearing loss. Doubling the distance between yourself and a loud sound can reduce the sound’s intensity by as much as one-fourth of what it was.

What is the Doppler effect? The Doppler effect is a change in the observed frequency when the sound source, the observer, or both are moving. When you and the source of sound are moving closer together, the sound waves are closer together. The sound has a higher frequency and higher pitch. When you and the source are moving away from each other, the waves are farther apart. The sound has a lower frequency and lower pitch. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 1 Sound Waves and Hearing

What is the Doppler effect? Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 1 Sound Waves and Hearing How are the frequencies changing in these two pictures?

Some Like It Hot Copyright © Houghton Mifflin Harcourt Publishing Company What affects the speed of sound? There are two main factors that affect the speed of sound: the type of medium the sound travels through, and the temperature of the medium. If we know these factors, we can predict the speed of sound. Unit 2 Lesson 2 Interactions of Sound Waves

Copyright © Houghton Mifflin Harcourt Publishing Company What affects the speed of sound? The speed of sound depends on the type of matter, or medium, through which sound travels. The state of matter also affects sound waves. Sound travels fastest through solids, slower through liquids, and slowest through gases. The more packed together the particles are, the faster the wave will travel. Unit 2 Lesson 2 Interactions of Sound Waves

Copyright © Houghton Mifflin Harcourt Publishing Company What affects the speed of sound? The speed of sound depends on the temperature of a medium. Sound travels faster at higher temperatures than at lower ones. Particles in a material move more quickly at higher temperatures and transfer energy faster. Sound moves faster at higher temperatures and slower at cooler temperatures. Unit 2 Lesson 2 Interactions of Sound Waves

Hello? Hello? Hello? Copyright © Houghton Mifflin Harcourt Publishing Company How do sound and matter interact? Sound waves do not travel easily through all matter. Sound may bounce away from some surfaces. Sound may be absorbed by other sources or transmitted through a barrier Reflection is the bouncing back of a wave when it hits a barrier. Sound waves reflect best off smooth, hard surfaces. Unit 2 Lesson 2 Interactions of Sound Waves

Copyright © Houghton Mifflin Harcourt Publishing Company How do sound and matter interact? Some matter absorbs sound waves better than other matter. A rough wall will absorb sound better than a smooth wall will. Soft materials, such as rugs and drapes, will absorb sound better than hard surfaces will. Unit 2 Lesson 2 Interactions of Sound Waves

Copyright © Houghton Mifflin Harcourt Publishing Company How do sound and matter interact? How will sound waves travel differently in each room? Echo? Unit 2 Lesson 2 Interactions of Sound Waves

What is an echo? Some animals—such as dolphins, bats, and beluga whales—use echoes to hunt for food and find objects in their path. The use of reflected sound to find objects is called echolocation. People use a type of echolocation called sonar (sound navigation and ranging). Sonar is electronic echolocation used to locate objects underwater. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 2 Interactions of Sound Waves

What is an echo? How do bats use echolocation? Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 2 Interactions of Sound Waves

How does interference cause sonic booms? Jet planes moving faster than the speed of sound can produce a very loud sound called a sonic boom. This sound can rattle and even break windows. When a jet travels very fast, it catches up to its own sound. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 2 Interactions of Sound Waves

How does interference cause sonic booms? The waves pile up as a result of constructive interference. This interference forms a high pressure area called a sound barrier. If a jet travels fast enough, it breaks through the barrier and forms a single shock wave that is heard as a loud boom. The jet must travel at supersonic speeds, or speeds faster than the speed of sound. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 2 Interactions of Sound Waves

How does interference cause sonic booms? How does this jet create a sonic boom? Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 2 Interactions of Sound Waves

Good Vibrations Copyright © Houghton Mifflin Harcourt Publishing Company What is resonance? Resonance happens when a sound wave matches the natural frequency of an object and causes the object to vibrate. Seashells singer breaking glass videovideo Bridge videovideo Unit 2 Lesson 2 Interactions of Sound Waves