D O N OW : 4/16 A radio wave broadcasts at 700 kHz and travels the speed of light (3x10 8 m/s). 1.What is the period? 2.What is the wavelength?

P ROPERTIES OF S OUND 4/6/11

S OUND WAVES Sound wave: a mechanical wave transmitted through matter (a material medium)

S OUND W AVES : Sound is a longitudinal wave:

P RESSURE V ARIATIONS Compression: particles closer together Rarefaction: particles farther apart

P ROPERTIES OF S OUND : P ITCH Pitch: The sensation of a frequency Higher pitch! 

M USIC Consonant: Certain sound waves which, when played simultaneously, will produce a pleasant sound IntervalFrequency Ratio Examples Octave2:1512 Hz and 256 Hz Third5:4320 Hz and 256 Hz Fourth4:3342 Hz and 256 Hz Fifth3:2384 Hz and 256 Hz

E XAMPLE : Two musical notes that have a frequency ratio of 2:1 are said to be separated by an octave. A musical note that is separated by an octave from middle C (256 Hz) has a frequency of _____. a. 128 Hz b. 254 Hz c. 258 Hz d. 345 Hz e. none of these

R EVIEW : A MPLITUDE Amplitude represents energy

P ROPERTIES OF S OUND : L OUDNESS Loudness depends on the amplitude of sound waves; measured in decibels (dB) Intensity ( I ): how loud a sound is in relation to another

SourceIntensity Level # of Times Greater Than TOH Threshold of Hearing (TOH)0 dB10 0 Rustling Leaves10 dB10 1 Whisper20 dB10 2 Normal Conversation60 dB10 6 Busy Street Traffic70 dB10 7 Vacuum Cleaner80 dB10 8 Walkman at Maximum Level100 dB10 Front Rows of Rock Concert110 dB10 11 Threshold of Pain130 dB10 13 Military Jet Takeoff140 dB10 14 Instant Perforation of Eardrum 160 dB10 16

E XAMPLE : A mosquito's buzz is often rated with a decibel rating of 40 dB. Normal conversation is often rated at 60 dB. How many times more intense is normal conversation compared to a mosquito's buzz ? a. 2 b. 20 c. 100 d. 200 e. 400

S PEED OF S OUND : The speed of sound depends primarily on medium but also on temperature: v = 331 m/s + (0.6 m/s/C)T

E XAMPLE : Determine the speed of a sound wave in air at a temperature of 20ºC. v = 331 m/s + (0.6 m/s/C)T v = 331 m/s + (0.6m/s/C)(20 C) v = 331 m/s + 12 m/s v = 343 m/s

E CHO : echo: a reflected sound; will take twice the time to travel the same distance Example: a sound wave travels 500 m to a cliff, then returns to where it started. If the sound wave traveled 330 m/s, how long does it take the sound to return to where it started?

P RACTICE : Use the rest of class to work on the worksheet “Sound Waves.” Be prepared to answer an exit question at the end of class

E XIT Q UESTION : 1. Which property of sound is determined by amplitude? 2. Which property of sound is determined by frequency?

D O N OW (4/17/12): 1. Which property of sound is determined by amplitude? 2. Which property of sound is determined by frequency? 3. What is the velocity of sound when the temperature is 44˚ C?

A GENDA : 4 th Q Project Homework questions Extra credit (optional)

F OURTH QUARTER PROJECT Deadline 1: TOMORROW Bring in your favorite piece of art, or any art piece that speaks to you. It can be a drawing, a painting, a sculpture, etc. You may make a photocopy, or print it from a computer, but you MUST have a hard copy with you… on your phone doesn’t count!!! You will also write a paragraph about your piece, but we will do that tomorrow.

P RACTICE : Work on homework Work on extra credit (optional) – if you want extra credit, the work must be submitted by the end of class Begin thinking about your art piece – feel free to look through your history or English textbook once you have finished your work.