Table of Contents • The Nature of Sound • Properties of Sound • Music • How You Hear Sound • Using Sound
- The Nature of Sound Sound Waves • Sound is a disturbance that travels through a medium as a longitudinal wave. As a gong vibrates, it creates sound waves that travel through the air.
- The Nature of Sound Interactions of Sound Waves • Sound waves reflect off objects, diffract through narrow openings and around barriers, and interfere with each other.
- The Nature of Sound The Speed of Sound • The speed of sound depends on the elasticity, density, and temperature of the medium the sound travels trough.
- The Nature of Sound Temperature and the Speed of Sound • The speed of sound in dry air changes as the temperature changes. The graph shows data for the speed of sound in air at temperatures from –10ºC to 20ºC.
The speed at –10ºC is325 m/s. Reading Graphs: What is the speed of sound in air at –10ºC? - The Nature of Sound Temperature and the Speed of Sound
The speed of sound increases as air temperature increases. Interpreting Data: Does the speed of sound increase or decrease as temperature increases? - The Nature of Sound Temperature and the Speed of Sound
At 30ºC, the speed of sound might be 349 m/s. Predicting: What might be the speed of sound at 30ºC? - The Nature of Sound Temperature and the Speed of Sound
- The Nature of Sound Elasticity • Elasticity is the ability of a material to bounce back after being disturbed. You can model elasticity by representing the particles in a medium as being held together by springs.
- The Nature of Sound Density • Density is how much mass there is in a give volume. The volumes of the cubes are the same, but the brass has more mass.
- The Nature of Sound Identifying Main Ideas • As you read the section “Interactions of Sound Waves,” write the main idea–the biggest or most important idea–in a graphic organizer like the one below. Then write three supporting details that further explain the main idea. Main Idea Sound waves interact with objects and with other sound waves. Detail Detail Detail Reflection occurs when sound waves strike a surface. Sound waves can diffract around corners and through openings. The interference of sound waves can be constructive or destructive.
- The Nature of Sound Links on Sound • Click the SciLinks button for links on sound.
- Properties of Sound Loudness • The loudness of different sounds is compared using a unit called the decibel (dB).
- Properties of Sound Pitch • The pitch of a sound that you hear depends on the frequency of the sound wave.
- Properties of Sound Changing Pitch • When you sing, you change pitch using your vocal cords. Your vocal cords are located in your voice box, or larynx.
- Properties of Sound The Doppler Effect • The change in frequency of a wave as its source moves in relation to an observer is called the Doppler effect. When a sound source moves, the frequency of the waves changes because the motion of the source adds to the motion of the waves.
- Properties of Sound The Doppler Effect • When the plane travels almost as fast as the speed of sound, the sound waves pile up in front of the plane. This pile up is the “sound barrier.”
- Properties of Sound Outlining Properties of Sound • An outline shows the relationship between main ideas and supporting ideas. As you read, make an outline about the properties of sound. Use the red headings for the main ideas and the blue headings for the supporting ideas. • Loudness • Energy of a Sound Source • Distance From a Sound Source • Measuring Loudness • Pitch • Pitch and Frequency • Changing Pitch • Doppler Effect • What Causes the Doppler Effect? • What Causes Shock Waves?
- Properties of Sound More on the Properties of Sound • Click the PHSchool.com button for an activityabout the properties of sound.
- Music Sound Quality • The sound quality of musical instruments results from blending a fundamental tone with its overtones. Resonance also plays a role in sound quality.
- Music Groups of Musical Instruments • There are three basic groups of musical instruments: stringed instruments, wind instruments, and percussion instruments.
- Music Previewing Visuals • When you preview, you look ahead at the material to be read. Preview Figure 15. Then write two questions that you have about the diagram in a graphic organizer like the one below. As you read, answer your questions. Musical Instruments Q. How is pitch changed in each type of instrument? A. By changing the frequency of the vibrations Q. How is the loudness changed in each type of instrument? A. By changing the energy of the vibrations
- How You Hear Sound The Human Ear • The outer ear funnels sound waves, the middle ear transmits the waves inward, and the inner ear transforms sound waves into a form that travels to your brain.
- How You Hear Sound Sequencing • Sequence is the order in which the steps in a process occur. As you read, make a flowchart that shows how you hear sound. Put the steps of the process in separate boxes in the order in which they occur. How You Hear Sound The outer ear funnels sound waves into the ear canal. Sound waves make the eardrum vibrate. Tiny bones in the middle ear transmit vibrations to the inner ear. Vibrations in the cochlea of the inner ear send messages to the brain.
- Using Sound Echolocation • Some animals, including bats and dolphins, use echolocation to navigate and to find food.
- Using Sound Sonar • A sonar device sends out ultrasound waves and then detects the reflected waves.
- Using Sound Comparing and Contrasting • As you read, compare and contrast echolocation and sonar by completing a table like the one below. Using Sound Feature Echolocation Sonar Ultrasound Ultrasound Type of wave Water Air, water Medium(s) Find water depth, sunken objects, schools of fish Navigate, find food Purposes
- Using Sound More on Sonar • Click the PHSchool.com button for an activity about sonar.
Graphic Organizer Sound travels as has properties Longitudinal waves Intensity Frequency speed depends on is heard as is heard as Elasticity Density Temperature Loudness Pitch