D O N OW : 4/16 A radio wave broadcasts at 700 kHz and travels the speed of light (3x10 8 m/s)....
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Transcript of D O N OW : 4/16 A radio wave broadcasts at 700 kHz and travels the speed of light (3x10 8 m/s)....
DO NOW: 4/16
A radio wave broadcasts at 700 kHz and travels the speed of light (3x108m/s).
1.What is the period?2.What is the wavelength?
http://www.physicsclassroom.com/class/sound/U11l2a.cfm
MUSICConsonant: Certain sound waves which, when played
simultaneously, will produce a pleasant sound
Interval Frequency Ratio
Examples
Octave 2:1 512 Hz and 256 Hz
Third 5:4 320 Hz and 256 Hz
Fourth 4:3 342 Hz and 256 Hz
Fifth 3:2 384 Hz and 256 Hz
EXAMPLE:
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 Hzb. 254 Hzc. 258 Hzd. 345 Hze. none of these
PROPERTIES OF SOUND: LOUDNESS
Loudness depends on the amplitude of sound waves; measured in decibels (dB)
Intensity (I): how loud a sound is in relation to another
10
'#
10sdB
ixII
Source Intensity Level
# of Times Greater Than TOH
Threshold of Hearing (TOH) 0 dB 100
Rustling Leaves 10 dB 101
Whisper 20 dB 102
Normal Conversation 60 dB 106
Busy Street Traffic 70 dB 107
Vacuum Cleaner 80 dB 108
Walkman at Maximum Level 100 dB 1010
Front Rows of Rock Concert 110 dB 1011
Threshold of Pain 130 dB 1013
Military Jet Takeoff 140 dB 1014
Instant Perforation of Eardrum
160 dB 1016
EXAMPLE:
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. 2b. 20c. 100d. 200e. 400
SPEED OF SOUND:
The speed of sound depends primarily on medium but also on temperature:
v = 331 m/s + (0.6 m/s/C)•T
EXAMPLE:
Determine the speed of a sound wave in air at a temperature of 20ºC.
v = 331 m/s + (0.6 m/s/C)•Tv = 331 m/s + (0.6m/s/C)•(20 C)v = 331 m/s + 12 m/sv = 343 m/s
ECHO: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?
PRACTICE:Use the rest of class to work on the worksheet “Sound Waves.”
Be prepared to answer an exit question at the end of class
EXIT QUESTION:
1. Which property of sound is determined by amplitude?
2. Which property of sound is determined by frequency?
DO NOW (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?
FOURTH QUARTER PROJECT Deadline 1: TOMORROWBring 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.