1. Sound

2. Nature and Origin of Sound Waves
Sound waves are longitudinal waves.
Sound waves are created from vibrations in a medium.
Sound travels fastest in solids when compared to liquids and gases.
Will sound travel in vaccuum? Justify your answer.

3. Revisiting Longitudinal Waves
Compressions:
Rarefactions:

4. Pitch and Frequency
The impression given by the frequency of a particular sound wave is described as pitch.
A young person can normally hear pitches with frequencies from about 20Hz to 20,000Hz.
As we grow older the window gets smaller and smaller.
Sound waves with frequencies below 20Hz are called infrasonic.
Sound waves with frequencies above 20,000Hz are called ultrasonic.
WE CANNOT HEAR INFRASONIC OR ULTRASONIC!

5. Echolocation
Echolocation: a phenomenon in which ultrasonic sound waves generated are reflected back to the source.
Example: bat, dolphins

6. Pitch and Frequency (cont..)
What really happens in a high frequency? What really happens in a low frequency?

7. Loudness and Speed of Sound
Loudness: is a physiological sensation used to describe the intensity of a sound.
The intensity of a sound is proportional to the square of the amplitude of a sound wave.
The unit for intensity/loudness is decibel (dB).
Speed of sound: can be described as how fast a wave of sound is travelling in time.
Factors affecting speed of sound:
Medium
Temperature: Higher the temperature greater the speed of sound. At 0 celsius the speed of sound is 300m/s; the speed of sound increases by 0.60m/s for every 1 degree increase.
3. Elasticity:

8. Resonance
Resonance: A phenomenon in which a forced vibration matches the natural frequency of a wave causing a drastic increase in amplitude.
Example: The Tacoma Narrows Bridge disaster in 1940 was due to wind resonance.

9. Resonance Cont..

10. Beats
Beats: are the sounds heard when two slightly different frequency waves travel simultaneously.

11. Beats (cont..)