1. Sound Chapter 15

2. Topics for Sound Sound wave propertiesSound wave properties Speed of soundSpeed of sound EchoesEchoes BeatsBeats Doppler shiftDoppler shift ResonanceResonance Anatomy of EarAnatomy of Ear

3. Sound Wave Properties

4. Sound Waves are Longitudinal Waves The air molecules shown below are either compressed together, or spread apart. This creates alternating high and low pressure.

5. Frequency The frequency of a sound wave (or any wave) is the number of complete vibrations per second. The frequency of sound determines its pitch. Human Hearing ranges from …. 20Hz to 20KHz

6. The higher the frequency, the higher the pitch

7. Wavelength Wavelength is the distance between two high pressures, or two low pressures. This property is dependent on the velocity of the sound and it’s frequency.

8. The Amplitude of a Sound Wave Determines its loudness or softness

9. Velocity of Sound

10. The velocity of sound depends on The medium it travels throughThe medium it travels through In air at room temperature sound travels at 343m/s (~766 mph)In air at room temperature sound travels at 343m/s (~766 mph) v = 331 m/s + (0.6)Tv = 331 m/s + (0.6)T –v: velocity of sound in air –T: temperature of air in o C

11. Relationship between velocity, frequency, and wavelength V = fV = f V = velocity of soundV = velocity of sound = wavelength of sound = wavelength of sound f = frequency of soundf = frequency of sound

12. Sound travels faster in liquids than in airSound travels faster in liquids than in air Sound travels faster in solids than in liquidsSound travels faster in solids than in liquids Sound does not travel through a vacuumSound does not travel through a vacuum –there is no air in a vacuum so sound has no medium to travel through

13. Echoes: REFLECTION

14. Echoes are the result of the reflection of sound Sound waves leave a source, travel a distance, and bounce back to the origin.

15. Things that use echoes... Bats Dolphins/ Whales Submarines Ultra sound Sonar

16. REFRACTION OF WAVES

18. Refraction of Sound as the sound wave propagate into the warmer air at lower levels, they change direction, much like light passing through a prism

20. DIFFRACTION: THE BENDING OF WAVES THROUGH A SMALL OPENING

21. BENDING OF A WAVE

22. Beats

23. A beat occurs when sound waves of two different (but very much alike) frequencies are played next to each other. The result is constructive and destructive interference at regular intervals.

24. Sound waves move out like this:

25. But when they move, the front of the wave gets bunched up (smaller wavelength) and the back of the wave starts to expand (larger wavelength):

26. C B A Observer C hears a high pitch (high frequency) Observer B hears the correct pitch (no change in frequency) Observer A hears a low pitch (lower frequency)

27. Police use the Doppler Shift when measuring your speed with radar A frequency is sent out of the radar gun The sound wave hits the speeding car The frequency is changed by the car moving away from the radar and bouncing back The amount the frequency changes determines how fast you are going The faster you are going, the more the frequency is changed.

28. When the source goes faster, the wave fronts in the front of the source start to bunch up closer and closer together, until...

29. The object actually starts to go faster than the speed of sound. A sonic boom is then created.

30. Resonance

31. Resonance happens with closed pipe resonators and open pipe resonators Resonance occurs when there is a standing wave in the tube Closed pipe resonators –open end of tube is anti-node –closed end of tube is node Open pipe resonators –both ends are open –both ends are anti-nodes

32. Closed pipe resonator

33. Open pipe resonator

34. Anatomy of the Ear

36. Pinna Sound starts at the Pinna

37. auditory canal Then goes through the auditory canal

38. Tympanic Membrane The sound waves will then vibrate the Tympanic Membrane which is made of a thin layer of skin.

39. Malleus IncusStapes The tympanic membrane will then vibrate three tiny bones : the Malleus, the Incus, and the Stapes

40. Cochlea The stapes will then vibrate the Cochlea

41. Inside look of the Cochlea The stapes vibrates the cochleaThe stapes vibrates the cochlea The frequency of the vibrations will stimulate particular hairs inside the cochleaThe frequency of the vibrations will stimulate particular hairs inside the cochlea The intensity at which these little hairs are vibrated will determine how loud the sound is.The intensity at which these little hairs are vibrated will determine how loud the sound is. The auditory nerve will then send this signal to the brain.The auditory nerve will then send this signal to the brain. 

42. SOUND INTENSITY: THE LOUDNESS OF SOUND

43. DECIBEL MEASURES THE LOUDNESS OF SOUND RELATES TO THE AMPLITUDE OF THE WAVE EVERY INCREASE OF 20dB HAS 10x GREATER AMPLITUDE

44. 150dBJET TAKING OFF 115dB CHAIN SAW 100dBPOWER MOWER 80dB NOISY RESTAURANT 75dB VACUUM CLEANER 50dBAVERAGE HOME 25dBPURRING CAT 20dB RUSTLING LEAVES 15dB WHISPER 0dB FAINTEST THAT CAN BE HEARD

45. A SOUND 10 TIMES AS INTENSE IS PERCEIVED AS BEING ONLY TWICE AS LOUD

46. NOISE POLLUTION · Prolonged exposure to noise greater than 85-90 dBA (decibels measured on the A- scale) may cause hearing loss · Brief exposures to noise sources of 100-130 dBA can cause hearing loss · A single exposure to a level of 140 dBA or higher can cause hearing loss

47. Hours Per Day Noise Level (dBA) 8 90 495 2*100* 1105 0.5110 EXPOSURE TO LOUD NOISE --that results in hearing loss