Unit 2 Lesson 2 Interactions of Sound Waves

Crest Trough Unit 2 Lesson 2 Interactions of Sound Waves

Unit 2Lesson 2 Interactions of Sound Waves Some Like It Hot 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 2Lesson 2 Interactions of Sound Waves 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 2Lesson 2 Interactions of Sound Waves 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 2Lesson 2 Interactions of Sound Waves Hello? Hello? Hello? 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 2Lesson 2 Interactions of Sound Waves 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 2Lesson 2 Interactions of Sound Waves How do sound and matter interact? • How will sound waves travel differently in each room?

Unit 2Lesson 2 Interactions of Sound Waves What is an echo? • An echo is a reflected sound wave. • The strength of the echo depends on the reflecting surface. • Echoes can be reduced using soft materials that absorb the sound waves. • Echoes can also be reduced using rough surfaces that scatter the sound waves.

Unit 2Lesson 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.

Unit 2Lesson 2 Interactions of Sound Waves What is an echo? • How do bats use echolocation?

Unit 2Lesson 2 Interactions of Sound Waves Boom! How do sound waves interact with each other? • Interferencehappens when two or more waves overlap and combine to form one wave. • In music, beats happen when two sound waves with nearly equal frequencies interfere. • Since the frequencies are not quite equal, they form a repeating pattern of constructive and destructive interference that sounds loud and soft.

Unit 2Lesson 2 Interactions of Sound Waves How do sound waves interact with each other? • When constructive interference occurs, waves overlap and combine to form a wave with a larger amplitude, or height. • Constructive waves can cause • very loud sounds, such as • sonic booms.

Unit 2Lesson 2 Interactions of Sound Waves How do sound waves interact with each other? • In destructive interference, waves combine to form a wave with a smaller amplitude. • The sound will be softer because • the amplitude is decreased. • Noise cancelling headphones use • destructive interference.

Unit 2Lesson 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.

Unit 2Lesson 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.

Unit 2Lesson 2 Interactions of Sound Waves How does interference cause sonic booms? • How does this jet create a sonic boom?

Unit 2Lesson 2 Interactions of Sound Waves Good Vibrations What is resonance? • Resonancehappens when a sound wave matches the natural frequency of an object and causes the object to vibrate. • If a sound wave in the room forces air in a seashell to vibrate at its natural frequency, resonance occurs. • This resonance results in a big vibration that sounds like the ocean when you hear it.

Unit 2Lesson 2 Interactions of Sound Waves Where can resonance occur? • All objects have a frequency, or set of frequencies, at which they vibrate. • These are called natural frequencies, or resonantfrequencies. • Resonance will happen whenever an object vibrating at or near the natural frequency of a second object causes the second object to vibrate as well.

Unit 2Lesson 2 Interactions of Sound Waves Where can resonance occur? • Resonance is important for making music. • Vibrations make a sound that gets louder when it forms a standing wave inside the instrument. • A standing waveis a pattern of vibration that looks like the wave is standing still. • Resonance occurs when standing waves are formed.

Unit 2Lesson 2 Interactions of Sound Waves Where can resonance occur? • Resonance can even occur in buildings, towers, and bridges. • Simple activities such as marching can create resonance to cause a bridge to sway or collapse. • Engineers plan their designs to prevent resonance that could collapse a structure. • Overlapping plates cause friction to keep resonance from becoming destructive.

Unit 2 Lesson 3 Sound Technology

Unit 2Lesson 3 Sound Technology Hello Hello Hello How are echoes used? • Echolocationis the use of echoes to find food and other objects. • Animals produce ultrasound, which are sound waves that have frequencies greater than 20,000 Hz, for echolocation. The frequencies of these ultrasonic waves are too high for humans to hear. • The time it takes for ultrasound to bounce off an object and return to the animal tells the animal how far away the object is.

Unit 2Lesson 3 Sound Technology How are echoes used? • Though people cannot send out or hear ultrasound, people can still use echolocation in various technologies. • Sonaris a system that uses echoes to determine the locations of objects or to communicate. • Sonar is used to map out ocean floors, find fish, avoid icebergs, and help visually impaired people navigate on land.

Unit 2Lesson 3 Sound Technology How are echoes used? • How is sonar used to map the ocean floor?

Unit 2Lesson 3 Sound Technology How are echoes used? • Ultrasound procedures use high-frequency sounds to produce images of the inside of a person’s body. • Ultrasound that has a frequency of 1 million to 10 million hertz can pass into a person’s body. • Ultrasounds do not harm human cells, like x-rays do.

Unit 2Lesson 3 Sound Technology How are echoes used? • The sound waves reflect when they meet internal organs. • The reflected waves create an image of whatever organ they bounce off of. • Ultrasounds are used to check how a fetus is growing in a mother’s body.

Unit 2Lesson 3 Sound Technology How do telephones transmit sound? • Sound waves lose energy over time. • Phones change sound waves into other types of signals that can be sent over long distances. • These signals are then changed back into sound waves that can be heard.

Unit 2Lesson 3 Sound Technology How do telephones transmit sound? • All telephones change sound into electrical signals. • Cordless phones change the electrical signal into radio waves that travel through air at the speed of light. • The base picks up the radio waves and changes them back into electrical signals that are sent through wires. • A computer sends these signals to the other phone, where they are changed back into sound waves.

Unit 2Lesson 3 Sound Technology Hello, Operator • People used to have to call telephone operators, who plugged wires into a switchboard to connect one phone to another. • The invention of the rotary dial made it possible for people to call a number directly, replacing telephone operators. • Cell phones use radio waves to send signals to phone towers. The towers transfer the signals to phone cables.

Unit 2Lesson 3 Sound Technology Groovy How is sound recorded and played back? • Sound is recorded to preserve sound information, such as interviews and music. • Thomas Edison invented the phonograph, which could record and play back sound. • Information in sound was recorded in the grooves of records. Now it is stored on CDs or in computer files.

Unit 2Lesson 3 Sound Technology How is sound recorded and played back? • A compact disc, or CD, is made of hard plastic. • The information in sound waves is stored by pressing microscopic pits into the plastic. • Light from a laser reflects off the shiny surface as the CD rotates. • The detector changes the pattern into an electrical signal, which is then changed back into sound waves.

Unit 2Lesson 3 Sound Technology How is sound recorded and played back? • Sound is also recorded as a digital file in a computer. • Digital files, such as MP3 files, store large amounts of information. • More sound files can be stored in a computer or an MP3 player than on a CD.

Unit 2Lesson 3 Sound Technology How is sound recorded and played back? • First, the original sound gets changed into an electrical signal. • Then, it is stored as a digital file on a hard drive. The digital file is a series of 1s and 0s. • Software reads the files and produces electrical signals that are sent to speakers. • The speakers change the signal back into sound waves.

Unit 2 Lesson 2 Interactions of Sound Waves