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====== Q3.1 Sound transfer in/between media: ======
{{ youtube>114G-ww90A0?640x360 |BBC - String Telephone - Sound Transmission Intensity & Amplification}}

**Video 1. Sound Transmission Intensity & Amplification**
  * IF UNABLE TO ACCESS YOUTUBE VIDEO (requires Flash) TRY:[[http://viewpure.com/114G-ww90A0|BBC - String Telephone - Sound Transmission Intensity & Amplification]]

++++ Q3.1 CLICK HERE TO SEE / HIDE STUDENT FLIP RESOURCES:|
CONCEPT: volume/amplitude can be affected by transmission medium, refraction and reflection.

when you strike one object with another, the sound created inside the solid object is louder that the same sound created in air

**UNSW INTERACTIVE - Pitch, Loudness & Timbre **
  * [[http://www.animations.physics.unsw.edu.au/waves-sound/sound/index.html|UNSW PhyClips - Waves & Sound]]

"Pressing our ear to a solid, for example, a door, allows us to directly hear the pressure waves travelling through the solid."

Reference: [[http://www.scootle.edu.au/ec/viewing/S7156/look-listen-2012/resources/look%20listen_comp.pdf|Primary Connections]]

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++++ Q3.1 CLICK HERE FOR A SCIENTIFIC EXPLANATION:|
CONCEPT:  Sound volume/amplitude can be affected by refraction and reflection.

When you put your cell phone on a table and when it vibrates its really loud compared to when its not on the table? Its because when the cell phone vibrates it forces the table to vibrate as well.

This is called forced vibration.

This is caused when an object of some type vibrates and hits or is sitting on another object which then starts vibrating the other object its sitting on by force, which also makes the sound of the vibrate louder because two things are vibrating.

Forced vibration is found in a lot of things because otherwise some things wouldnt be loud enough to hear without it. Like in a acoustic guitar, the strings wound be faint without the wooden body because therer would be no way of hearing a sound in front of large audiences, even small audiences. Wooden bodies to an instrument is always needed to hear the instrument clearly.

Source: https://thescienceclassroom.wikispaces.com/Sound

when you strike one object with another, the sound created inside the solid object is louder than the sound created in the surrounding air. 

Sound 'coupling', also has a big effect: The technical term is 'mismatched impedances', but intuitively you may see how it is hard for air molecules to shake something of high density and vice versa. So, a lot of the energy gets trapped/reflected and never makes it from one medium into the other. 

So, before we decide or set out to prove that solids are better conductors, first make sure that we aren't accidentally putting louder sound into the solids in the first place.

http://www.eskimo.com/~billb/miscon/miscon4.html#sound
 
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====== Q3.4 How sound moves through air: ======

CONCEPT: Sound is a mechanical wave of vibrating particles

++++ Q3.4 CLICK HERE TO SEE / HIDE STUDENT FLIP RESOURCES:|
{{ youtube>EOQyMK9LopQ?640x360 |BBC Transmission of sound}}

**LONGITUDINAL WAVES (sound):**
  * IF UNABLE TO ACCESS YOUTUBE VIDEO (requires Flash) TRY:[[http://viewpure.com/EOQyMK9LopQ|BBC Transmission of sound]]

Sound waves are 'longitudinal' waves. Sound move through air by making air particles vibrate against each-other.

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++++ Q3.4 CLICK HERE IF YOU CANNOT VIEW YOUTUBE VIDEO(S) ABOVE|
{{ :learn:sound:quiz:bbc-tansmission-of-sound.mp4?640x360 |BBC Transmission of sound}}

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++++ Q3.4 CLICK HERE FOR A SCIENTIFIC EXPLANATION:|
Please see this site for highly detailed and accurate information about sound waves [[http://www.acs.psu.edu/drussell/demos.html|Dan Russell - Sound wave animation library]].

The following information has been released under Creative Commons License and images have been copied from the above site:

In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. The animation (Fig 1.) shows a one-dimensional longitudinal plane wave propagating down a tube. The particles do not move down the tube with the wave; they simply oscillate back and forth about their individual equilibrium positions. Pick a single particle and watch its motion. The wave is seen as the motion of the compressed region (ie, it is a pressure wave), which moves from left to right.


{{:learn:sound:waves:longitudinal-wave-01.gif|Longitudinal Wave - compression}}

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**[[:learn:sound:discover:q03:home|CLICK HERE & SEE MORE DISCOVERY ACTIVITIES ABOUT THIS QUESTION]]**

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