2. Sound Waves

3. Sound A form of energy that causes molecules of a medium to vibrate back and forth in a series of compressions and rarefactions as a longitudinal wave http://static.howstuffworks.com/gif/noise- canceling-headphone-8.jpg

4. Characteristics of Waves Amplitude; The maximum distance that molecules are displaced from their resting position. Indicates the energy of wave. http://www.bargerbarger.com/pers onal/wp- content/uploads/2008/05/wave.png

5. Characteristics of Waves Wavelength; The distance between 2 consecutive crests or troughs of a wave measure in centimeters and meters. http://www.astro.cornell.edu/academ ics/courses/astro2201/images/wavel ength.gif

6. Characteristics of Waves Frequency; The number of complete waves or complete cycles per unit of time. Measured in Hertz Hz http://www.open2.net/open2static/s ource/file/root/1/0/26/263839/wave _length_choc_diag3.jpg

7. Characteristics of Waves Sound waves also have the characteristic of interaction.

8. Determining sound Intensity Frequency Quality

9. Following Effects on the Human Ear Loudness Pitch Timbre

11. Intensity and Loudness The amount of energy in a wave determined by the amplitude of sound wave. Large Amplitude = Large Intensity = Increased Loudness Measured in Decibels

12. Frequency and Pitch Pitch How high or low the sound is (NOT how loud or soft). Determined by frequency High frequency = High pitch Measured in Hertz (Hz) Human ears can hear in a range from 20 to 20,000 Hz.

13. Ultrasonic A pitch or frequency higher than 20,000 hertz. http://vb- lessenergy.com/sonic_sound_files/page1 2_1.jpg

14. Sonar Uses ultrasonic waves to detect solids. http://mainland.cctt.org/istf2006/i mages/496px- Sonar_Principle_EN.svg%5B1%5 D.png

15. Transmitting Sound Requires a Medium

16. 2 Things that Affect the Transmission of Sound 1. Elasticity of Materials Materials that are more elastic transmit sound easier. Metals/Solids are more elastic than liquids and gases.

17. 2 Things that Affect the Transmission of Sound 2. Arrangement of molecules of the medium. Molecules that are close together transmit sound easier. Solids transmit best because the molecules are close together. A long time ago people would put their ear on the railroad tracks to see how close the train was.

18. Speed of Sound In the air it is approximately 340 m/s. Affected by 2 factors: Temperature As temperature increases speed of sound increases. Nature of the medium Sound travels faster in the most elastic materials Density increases speed of sound decreases.