3. Like all waves, sound waves are produced by a vibration.  A tuning fork vibrates to produce a sound.  A guitar string vibrates to produce a sound.  Your vocal cords vibrate to produce a sound.  A tree that falls in the woods causes a vibration and produces a sound– even if no one is around to hear it!!!!!!!

4. Sound Waves are Longitudinal Waves. As the fork moves forward and back it alternately compresses and then decompresses the air (or whatever medium it is traveling through). From above the source it looks more like this:

5. Sound Waves are Mechanical Waves This means they MUST have a medium (matter) to travel. This means sound waves CANNOT travel through empty space ( a vacuum).

6. The Amplitude of a Sound Wave is related to the density of the compressed part of the wave. The more dense the compression the higher the amplitude. The Amplitude for a sound wave is related to its Loudness. The larger the amplitude the louder the sound. So next time you want your friend to turn up the music, just ask them to increase its amplitude!!!!!

7. The frequency of a sound wave is related to its pitch. The higher the pitch the higher the frequency. Pitch is subjective: Two people can disagree about whether a sound has a high pitch or a low pitch. Frequency is objective: 262.5 Hz < 430 Hz

8. All sound travels at the same speed in the same medium. This speed is called the speed of sound. The speed of sound in air is : 343 m/s (767 mph) The speed of sound in water: 1433 m/s (3206 mph) The speed of sound in concrete: 3400 m/s (7606 mph) The speed of sound in steel: 6100 m/s (13645 mph)

9. Sound & the Wave Equation v = λ f High frequency sound has a short wavelength. Low frequency sound has a long wavelength.

10. What is the wavelength of a sound wave that has a frequency of 440 Hz (A)? Assume the speed of sound is 343-m/s. Know: v = 343-m/s f = 440 Hz Find: λ = ? Equation: Solve: v λ f

11. Whenever a source of sound is moving, the pitch you hear depends on whether the sound source is moving towards you or away from you.

12. The Doppler Effect