Slide 1

SOUNDWAVES

Sound WavesA sound wave is a wave of alternating high-pressure and low-pressure regions of air.

How are Sounds Made?When someone or something makes a sound, the air molecules around it vibrate, or move back and forth, and they push into the molecules in front of them. This starts a chain reaction.

Can there be sound in outer space?Your Turn

Factors that Affect the Speed of SoundSpeed of sound depends on:1. Elasticity = ability to bounce backFaster if more elasticSolids are more elastic than liquids or gases so sound travels fastest through solids

2. Density For materials in the same state of matterSlower in more dense objects- particles do not move as fast because there is more matter in a given area

3. TemperatureSlower in lower temperatures (sluggish)Faster in higher temperatures

Doppler Effectis the apparent change in the frequency of a sound caused by the motion of either the listeneror the source of the sound. Captain Chuck Yeager

Supersonic Flight

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DREVIEW

Doppler Effectthe change in the frequency of a sound caused by motion

II. Properties of Sound

Speed of SoundMedium velocity m/secair (20 C) 343air (0 C) 331water (25 C) 1493sea water 1533diamond12000iron 5130copper 3560 glass 5640Loudness= AmplitudeHow loud or softMeasured in decibels (dB)Low amplitude= softHigh amplitude= loud

Pitch= FrequencyHow high or low

Measured in Hertz

low frequency = low pitch, ex. rumble of a big truck

high frequency = high pitch, ex. whistle or siren

Fun Fact: women have higher frequencies than men.

Loudness of Sound in DecibelsSoundLoudness (dbs)Hearing DamageAverage Home40-50Loud Music90-100After long exposureRock Concert115-120ProgressiveJet Engine120-170PainHumans can hear from 20 Hz to 20,000 Hz

Ultrasound - sound waves with frequencies above the normal human range of hearing. Sounds in the range from 20-100kHz Infrasound - sounds with frequencies below the normal human range of hearing.Sounds in the 20-200 Hz range

Pitch= Frequency Resonance the frequency of sound waves exactly matches the natural frequency of an object.

http://www.youtube.com/watch?v=O9FrMkhQoA4&feature=related

http://www.youtube.com/watch?v=oXV45t6wlWU

How we hear a. Outer ear collects sound. b. Middle ear amplifies sound. c. Inner ear converts sound.

Musical sound

a. Noise has no pattern. b. Music has a pattern and deliberate pitches. c. Sound quality describes differences of sounds that have the same pitch and loudness. d. Every instrument has its own set of overtones.