1. Sound Basics Overview What is sound Speed Frequency Range

2. Students will… Know what causes sound Predict how the speed of sound changes through various materials Define different frequency ranges and how the human ear detects them

3. Hearing Stereoscopic

4. The Ear The outer ear consists of the ear canal that terminates at the eardrum Just behind the eardrum is the middle ear The bones in the middle ear transmit sounds to the inner ear The ear detects very small pressure fluctuations As a result, the ear is very susceptible to hearing damage

6. Producing a Sound Wave Something has to vibrate Sound waves are longitudinal waves traveling through a medium A tuning fork can be used as an example of producing a sound wave

7. Tuning Fork The vibrating tuning fork creates a succession of compressions and rarefactions Compressions Rarefaction s

8. A sinusoidal curve can be used to represent the longitudinal wave  Crests correspond to compressions  Troughs correspond to rarefactions

9. Speed of Sound in Air Main point: The higher the temperature the faster the sound wave moves!

10. Speed of Sound, General The speed of sound is  faster in solids than in gases  slower in liquids than in solids

11. Predict: in which is sound faster? 1. Air at the north pole or equator 2. Air during the summer or winter 3. Water or air 4. Steel or water 5. Big gummies or smaller gummies

12. Categories of Sound Waves Audible waves  Lay within the normal range of hearing of the human ear  Normally between 20 Hz to 20,000 Hz Infrasonic waves  Frequencies are below the audible range  Earthquakes are an example Ultrasonic waves  Frequencies are above the audible range  Dog whistles are an example

13. Hearing Test!

14. The Threshold of hearing is strongly dependent on frequency Which is the easiest frequency to hear? ~ 3300 Hz When the sound is loud (top curve, threshold of pain) all frequencies can be heard equally well. Frequency Response Curves

15. Applications of Ultrasound Can be used to produce images of small objects Widely used as a diagnostic and treatment tool in medicine  Ultrasonic flow meter to measure blood flow  Ultrasounds to observe babies in the womb  Cavitron Ultrasonic Surgical Aspirator (CUSA) used to surgically remove brain tumors Ultrasonic ranging unit for cameras

16. Applications of Ultrasound