1. Introduction to Sound Sound is a longitudinal wave with sufficient frequency and energy to stimulate the ear All sound starts with some source of vibration (f sound = f source ) Sound must have a medium in which to travel Parts of a sound pulse (V=f*λ)

2. The Velocity of Sound The velocity of sound (like all waves) is medium dependent V sound in air at STP (0  C and 1 ATM pressure) = 331 m/sec (1125 ft/sec, or 768 mph) The velocity of sound is temperature dependent! The velocity of sound will increase 0.6 m/sec for every 1  C increase Example – What is the speed of sound at room temperature of 23  C? Ans: (23 x 0.6) + 331 = 345 m/sec V sound in water = 1440 m/sec Supersonic – faster than the speed of sound Mach- How many times the speed of sound Mach 2 = 2x the speed of sound

3. Frequency of Sound The range of human hearing 20 Hz- 20,000 Hz (20 KHz) Pitch – the greater the frequency the greater the pitch that we hear Subsonic – f < 20 Hz Ultrasonic – f > 20 KHz

4. Loudness of Sound Loudness vs. Sound Intensity Loudness – What we perceive (subjective) Sound Intensity – A physical measurement of [(Joule/sec) /square meter] measured in (Watts/m 2 ) – (Objective) 0 dB –Threshold of Hearing 120 dB – Threshold of Pain The Decibel (dB) Scale

6. Hallway Noise (without students)

7. Hallway Noise (with students)

8. Homecoming Pep Assembly 1995

9. Battle of the Bands

10. Video http://www.youtube.com/watch?v=dke2i- xO1uohttp://www.youtube.com/watch?v=dke2i- xO1uo http://www.youtube.com/watch?v=- 1ywUmBpVGYhttp://www.youtube.com/watch?v=- 1ywUmBpVGY http://www.youtube.com/watch?v=fmbH1A pUG8Mhttp://www.youtube.com/watch?v=fmbH1A pUG8M

11. Reflection of Sound Echo – A returned sound pulse Ex- A sound pulse is emitted from a horn and its echo is detected 3 seconds later. If the temperature of the air is 20  C, how far away is the reflective surface? (20 x 0.6) + 331 = 343 m/sec V= d/t 343 = d/1.5 Ans: 514.5 m