We are starting with our QUIZ! Warm-Up 11/19/13 We are starting with our QUIZ!

The Nature and Properties of Sound 11-19-13

Sound In General Created by something that vibrates Travels as a compressional wave through a medium (solid, liquid, or gas)

1. The Speed of Sound Depends on the medium Fastest in solids, slowest in gases Sound waves travel faster when molecules are closer together!

Cont… Temperature also affects speed: higher temperatures mean higher speeds as the molecules move faster Speed does NOT depend on how loud the sound is Air Temperature (degrees C) Speed of Sound (m/s) 331 20 343

2. Loudness and Intensity Loudness=the human perception of intensity Louder waves carry more energy Remember: energy depends on amplitude (how dense the compressions are) Sound Loudness (dB) Purring cat 25 Vacuum 75 Chain Saw 115 Jet Plane Lift Off 150

Cont… Intensity= the amount of energy that flows from a certain area in a specific amount of time Higher intensity means louder sound

Cont… Intensity decreases with distance Energy (E) in the wave is converted to other forms of E along the way Low intensity waves lose energy more quickly Like a bouncing ball!

3. Pitch Pitch= how high or low a sound seems to be As frequency of a wave increases, so does the pitch!

Cont… Humans most sensitive to frequencies from 20 Hz to 20,000Hz Ultrasonic= frequencies above 20,000Hz (we can’t hear them) Ex) waves used in medical treatment Infrasonic= frequencies below 20 Hz (also can’t hear them) Ex) Earthquakes

4. The Doppler Effect Due to changes in pitch or frequency with a moving wave source Occurs whether it is the source or observer moving

Cont… Pitch/frequency increases as source moves toward observer Decreases as it moves away

Your Job! Sound Idea Rake worksheet (we are starting this together!) Everyone doing Unit 4 Retake Tomorrow TEST ON FRIDAY