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?

PROPERTIES OF SOUND4/6/11

SOUND WAVES

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

SOUND WAVES:

Sound is a longitudinal wave:

PRESSURE VARIATIONS Compression: particles closer together Rarefaction: particles farther apart

PROPERTIES OF SOUND: PITCH Pitch: The sensation of a frequency

Higher pitch!

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

REVIEW: AMPLITUDE Amplitude represents energy

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?

AGENDA:

4th Q Project Homework questions Extra credit (optional)

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.

PRACTICE:

Work on homeworkWork 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.