Chapter+26

​**Key Definitions** **: **

1.**__Beats-__**A throbbing variation in the loudness of sound caused by interference when two tones of slightly different frequencies are sounded together. 2. __**Resonance**__ - A phenomonenon that occurs when the frequency of forced vibrations on an object matches the objects natural frequency. 3. **__Compression__** - A pulse of compressed air; opposite of rarefaction 4.**__Rarefaction__**- A disturbance in air (or matter) in which the pressure is lowered; opposite of compression 5__**.Natural frequency-**__A frequency at which an elastic object,once energized,will vibrate.

**Notes:**
 * All sounds are produced by the vibrations of material objects.
 * Sound waves with frequencies below 20 hertz are called infrasonic.
 * Frequencies above 20,000 hertz are called ultrasonic.
 * For all wave motion, it is not the medium that travels across the room but a pulse that travels.
 * Sound waves are longitudinal and are compression and rarefraction.
 * Material and temperature affects the speed of sound.
 * Sound waves are a series of high and low pressure regions.
 * Loudness is a physiological sensation sensed in the brain.
 * When the frequency of a forced vibration on an object matches the objects natural frequency, a dramatic increase in amplitude occurs.
 * When a compression of one fork overlaps a compression from the other the sound is maximum.

**Pictures:**



[] 5 lessons dealing with sound [] a website dealing with sound and light
 * Links: **


 * Test Questions: **.
 * 1) What kind of wave is a sound wave? Transverse or Longitudinal
 * 2) What term applies to how low or how high sound frequencies appear to be? Forced Vibration, Pitch or Beats
 * 3) For all wave motion, it is not the medium that travels across the room, but a pulse that travels. T or F
 * 4) The energy in the compression travels along a spring. T or F
 * 5) All sounds are produced by vibrations. T or F
 * 6) What does sound travel through? A. Air B. solids C. liquids D. all of the above
 * 7) Interference affects the loudness of sound? T or F
 * 8) How far away is a storm if you have a 5 second delay between a lightning flash and the sound of thunder? a. 1 km b. 1 mile c. 25 miles d. 10 miles
 * 9) Compression is when air molecules are pressed together? T or F
 * 10) Rarefaction is when air molecules are being pressed together? T or F

**Record the aswers to the above questions at the link below** Answers to Test Questions