How Sound Travels Sound is a mechanical wave It moves by vibrating particles in: –Solids –Liquids –Gases Sound can not travel in a vacuum (empty space)!!! Speed of sound is affected by material: –Solids- fastest –Gases – slowest Speed of sound is affected by temperature: –Higher temp. – faster –Lower temp. - slower

Pitch Pitch is determined by the frequency of the sound wave –Low frequency = low pitch –High frequency = high pitch Pitch is measured in Hertz (waves per second) Infrasound – lower pitch than detected by human ear Ultrasound – higher pitch than detected by human ear

Intensity Intensity is determined by the amplitude of the sound wave –High amplitude = high intensity –Low amplitude = low intensity Intensity is measured in decibels Sounds greater than 90 decibels can damage hearing Sound intensity can be controlled: –Muffling –Amplification

Uses of Sound Waves In the medical field: –Ultrasound is used to get images of inside the body In communications: –Telephones, radios Sonar: –Used by ships, submarines to navigate In nature: –Bats, porpoises, whales and other animals use echolocation To make music: –Stringed instruments –Wind instruments –Percussion instruments