SOUND WAVES

A. Sound waves are longitudinal.

B. Sound waves are mechanical- they need a medium and a

vibration.

C. Sound does not travel in a vacuum.

Sound Waves

VELOCITY OF SOUND

At STP sound travels 3.31 x 102m/s

> It’s 4 times faster in water.

> It’s 15 times faster in metal.

Will change due to temperature:

v = 331m/s + 0.6(T)

(T is in Celsius)

Sound is a range of wave frequencies that the ear is sensitive to. (20Hz- 20,000Hz)

Infrasonic sound- Sounds lower than 20Hz

Ultrasonic sound- frequencies higher than 20,000Hz

Transmission Range- frequencies an organism can produce ( humans 85- 1000Hz)

Hearing Ranges

How does the ear work? The outer ear “catches the sound waves”. The middle ear takes the sound waves

and “vibrates” the eardrum. The inner ear sends the messages to the

brain.Middle Ear

Inner Ear

http://www.youtube.com/watch?v=pCCcFDoyBxM

Outer Ear

Talking

• http://www.youtube.com/watch?v=JzyHKYQzPBk

• http://www.youtube.com/watch?v=d-XbjFn3aqE

FREQUENCYFrequency- the

number of vibrations per second. How the ear identifies this vibration is called pitch. Pitch and frequency are directly proportional.

High Pitch

Low Pitchhttp://www.animations.physics.unsw.edu.au/jw/sound-pitch-loudness-timbre.htm

FUN INFO

The phone company uses a combination of frequencies to make a unique sound for each number on the phone.

#1 is 687Hz and 1209Hz

#2 is 687Hz and 1336Hz

#3 is 687Hz and 1477Hz

http://soundbible.com/tags-dial.html

AMPLITUDE

Amplitude- the maximum displacement of the particles from equilibrium. Amplitude determines the intensity of the sound and how loud it is.

http://www.animations.physics.unsw.edu.au/jw/sound-pitch-loudness-timbre.htm

SOUND INTENSITYSound Intensity- the

rate of flow of sound energy from a source. Measured in decibels or watts/meter2

According to OSHA 85dB and higher will produce permanent hearing damage.

HOMEWORK

• FROM TEXT BOOK

pg 369 #21-23 and #25-30

Show all formula’s and calculations!