The Nature of Sound Chapter 21

Objectives: THINK: Why is sound important? Physical Standard 1 I will be able to describe sound wave characteristics that are common among other forms of waves. I will be to differentiate unique characteristics of sound. THINK: Why is sound important?

Close Your Eyes and Listen: Click Click Click Click Click Click

Sound waves Interactions of sound Reflection travels through a medium (solid, liquids or gases) longitudinal wave Sound travels by sending vibrations -back and forth motion - through matter Pair and Share: Why can’t you hear sound in outer space? How do they communicate with each other? reflected sound called an echo hard, smooth surface = stronger reflection

Reflection Sound Waves

REVIEW WAVE: Refraction Diffraction Interference Bending of sound waves as it passes from one medium to another Bending of waves around a barrier sound waves meet constructive increases sound destructive decreases sound at room temp, sound travels at 343 m/s speed depends on medium it travels though Refraction Diffraction Interference Illustrate the three above Speed of Sound

Mediums and Sound Elasticity Density Temperature more elastic a medium faster sound travels Solid: fastest speed Liquid: medium speed Gas: slow speed Vacuum: no sound sound travels slower in dense materials sound travels slower at lower temperatures and higher altitudes Pair and Share: Why does this happen? Elasticity Density Temperature

Properties of Sound describes your perception of the energy of a sound describes what you hear depends on 2 factors: energy of sound source distance from sound source The Coolest Things Sound Wave Can Do Find someone and share video Loudness A medium is a material that sound, a form of energy, need to transfer Speed of sound Solid : Fast speed Liquid : Medium speed Gas : Slow Speed Standard Temperature and Pressure = 3.31 x 102 m/s Vacuum : No Sound

Energy of a sound source Think: Draw an example Distance from a sound source greater energy used  louder sound more energy  greater amplitude (vibration) large amplitude loud sound loudness increases the closer you are to a sound source

amount of energy a sound wave carries per second through a unit area greater intensity sounds louder unit decibel (dB) sound barely heard = 0 dB sound louder than 100 dB can damage ears Intensity Measuring Loudness

Pitch Pitch & Frequency Pitch and Frequency Video description of how high or low the sound seems to a person depends on frequency of the wave high frequency  higher pitch low frequency  low pitch can hear sounds with frequency between 20 Hz and 20,000 Hz

Ultrasound Infrasound Doppler Effect sound waves with frequency above normal human range frequency below human range of hearing change in frequency of a wave as its source moves in relation to an observer change in frequency is heard as a change in pitch

Shock Waves Sound Quality shock waves form as sound waves overlap release huge amounts of energy sonic boom heard when they pass by Blending of several pitches through interference

Noise Music Random mix of frequencies that are not pleasing set of frequencies that combine in patterns that are pleasing

How you Hear Sound function: gather sound waves and send info to brain three main sections: outer, middle, inner collects sound waves and directs them to ear canal which vibrates eardrum Human Ear Outer Ear

Middle Ear Inner Ear contains 3 small bones that increase size of vibrations Vibrations are changed into electrical signals for the brain to interpret

can occur if eardrum is damaged loud sounds can damage hair cells in inner ear won’t get messages to brain old age hair cells gradually die harder to hear amplify sound Hearing Loss Hearing Aids

-use of reflected sound waves to determine distances or locate objects -animals use this to navigate and find food  Bats, dolphins Echolocation