1. Sound and Hearing Properties of Sound Waves, Ultrasound, The Doppler Effect

2. Properties of Sound Waves Sound waves are longitudinal waves – compressions and rarefractions that travel through a medium The speed of sound varies depending on the medium

3. Properties of Sound Waves Sound travels fastest in solids, slower in liquids and slowest in gases This is due to the fact particles are closer together in solids The speed also depends on the density of the medium and how elastic the medium is

4. Properties of Sound Waves Intensity is the rate at which a wave’s energy flows through a given area Sound intensity depends on both the wave’s amplitude and the distance from the sound source If someone whispers in your ear it may be more intense than someone shouting across a field

5. Properties of Sound Waves Sound intensity is measured in decibels It is based on a scale of 10 Every 10-decibel increase is a tenfold increase For example: a 20 decibel sound is 100 times greater than a 0 decibel sound 15-20 decibels 120-160 decibels

6. Frequency and Pitch The frequency of a sound wave depends on how fast the source of the sound is vibrating Pitch is the frequency of a sound as you perceive it High-frequency sounds have a high pitch, low frequency sounds have a low pitch Pitch also depends on your health and age

7. Ultrasound Most people hear between 20Hz and 20,000Hz Infrasound is sound at frequencies lower than what people can hear Ultrasound is sound at frequencies higher than what people can hear

8. Sonar Sonar is used to detect distance under water Sonar stands for: sound navigation and ranging The distance of an object is calculated by the time it takes the sound wave to reach the object and the echo to return

9. The Doppler Effect The Doppler effect is a change in sound frequency caused by the motion of the sound source, motion of the listener, or both As the source of a sound moves closer a person hears a higher frequency, as the source moves away the person hears a lower frequency