Do Now:

1. Do Now:Have a HW pass? Turn it in for extra credit! Claim your POSTERS in the back of the room! Then, take a clicker and try these 2 problems – HINT – you may need to reference #17 in your Ch 26 POGIL • A bat flying in a room temperature cave emits a sound pulse and receives its echo in 1 second. How far away is the cave wall? • A sound travels in room temperature air. It takes 0.03 seconds for one sound wave to occur. • What is the wavelength of the sound wave? • Can a human hear this sound wave? • Can a dog hear this sound wave?

2. Do Now: 1. A bat flying in a room temperature cave emits a sound pulse and receives its echo in 1 second. How far away is the cave wall? • What do we know? • Room temperature air = sound wavespeed of 340 m/s • Wavespeed = distance traveled / time • 340 m/s = 340m / 1s • Which means that since it was an ECHO, the cave wall is 170 m away! • (travels 170 m there, and 170 m back, for a total distance of 340 m)

3. Regarding #1, how do you feel? • I have no clue what is going on • I think I’ll be ok with more practice • I did not get this correct the first time, but I know how to fix my error in the future • I got this correct the first time and I know what I am doing sow ell I could teach it to others!

4. Do Now: • A sound travels in room temperature air. It takes 0.03 seconds for one sound wave to occur. • What is the wavelength of the sound wave? • Can a human hear this sound wave? • Can a dog hear this sound wave? What do we know? • Room temperature air = sound wavespeed of 340 m/s • 0.03 seconds for one sound wave is the period • Frequency = 1/ period • f = 1/ (0.03)  f = 33.3 Hz (in other words, there are 33 waves per second)

5. Do Now: • A sound travels in room temperature air. It takes 0.03 seconds for one sound wave to occur. • What is the wavelength of the sound wave? • Can a human hear this sound wave? • Can a dog hear this sound wave? • = 33.3 = 10.2 m

6. #2 – can a human hear this sound? (f= 33.3 Hz) • Yes • No • Not sure

7. #2 – can a dog hear this sound? (f= 33.3 Hz) • Yes • No • Not sure

8. Regarding #2, how do you feel? • I have no clue what is going on • I think I’ll be ok with more practice • I did not get this correct the first time, but I know how to fix my error in the future • I got this correct the first time and I know what I am doing sow ell I could teach it to others!

9. Can ‘frequency’ be measured? • Yes • No • Not sure

10. Can ‘pitch’ be measured? • Yes • No • Not sure

11. What is the average frequency range of a young person’s hearing? • 20 Hz to 20 kHz • 10 Hz to 20 Hz • 20 Hz to 200 Hz • 20 Hz to 20,000 kHz • Not sure CAREFUL!!! 1 kHz = 1000 Hz

12. Older humans typically have a ____ hearing range than younger people, especially on the ___ frequency side. • bigger, high • bigger, low • smaller, high • smaller, low • Not sure Be nice to your grandparents!

13. Sound travels in a ______wave. • Transverse • Longitudinal • Not sure

14. Important DISCLAIMER: Many of the diagrams represent a sound wave by a sine wave, which resembles a transverse wave and may mislead people into thinking that sound is a transverse wave. Sound is not a transverse wave, but rather a longitudinal wave. Nonetheless, the variations in pressure with time take on the pattern of a sine wave and thus a sine wave is often used to represent the pressure-time features of a sound wave. In English: Machines that measure LOUDNESS have a screen that displays a sine wave to model the readings.

15. Infrasonic sounds are ____ than ___ Hz. • More, 10 • More, 20 • More, 20,000 • Less, 10 • Less, 20 • Less, 20,000 • Not sure

16. Ultrasonic sounds are ____ than ___ Hz. • More, 10 • More, 20 • More, 20,000 • Less, 10 • Less, 20 • Less, 20,000 • Not sure

17. Light CAN travel through a vacuum (evidence – we see sun, moon, stars, etc…)… but can SOUND travel through a vacuum? • Yes • No • Not sure Science fiction = WRONG! FICTION!

18. *You are about to read a ‘Bones’ definition. Not from the book, but it might make a little more sense* Remember – ELASTIC means an object can be thrown against a wall and not be smashed/ disfigured!What is MORE ELASTIC, putty or steel? • Putty • Steel • Not sure

19. Does sound travel better in elastic or inelastic solids? • Elastic • Inelastic • Not sure

20. The speed of sound in dry, ROOM TEMPERATURE air is about… • 330 m/s • 340 m/s • Not sure

21. Sound travels fastest to slowest in the following order: • Solids, liquids, gasses • Solids, gasses, liquids • Gasses, liquids, solids • Gasses, solids, liquids • Liquids, solids, gasses • Liquids, gasses, solids • Not sure

22. Sounds travels _____ in a hotter medium, than the identical medium that is colder • Faster • Slower • The same • Not sure Hotter = more energy = easier for sound to ‘bounce’ thru the medium!

23. Sounds travels _____ humid air, than dry air of identical temperature • Faster • Slower • The same • Not sure Humid = closer to liquid!

24. True or false: INTENSITY of a sound can be measured. • True • False • Not sure

25. True or false: LOUDNESS of a sound can be measured. • True • False • Not sure It is our SUBJECTIVE interpretation of intensity

26. The intensity of a sound is__________ proportional to the amplitude squared of the sound wave • Directly • Inversely • Not sure

27. True or False: Sound cannot cancel sound. • True • False • Not sure BOSE/ Beats headphones, white noise machines, construction headphones

28. True or False: The 2 pennies in this demo are made from identical materials. • True • False • Not sure Natural frequency

29. The tuning fork on table is an example of…. • Resonance • Forced vibration • Beats • Not sure Like acoustic guitars

30. CH 26 - Sound Notes - Set 2 • We are doing 4 demos together • Doppler Ball – what do you hear as it APPROACHES you? As it goes AWAY from you? • Mosquito Ring Tone: listen for a TONE. NOT STATIC!!!! Raise your hand if you CANNOT hear a tone. (If you only hear static, raise your hand! Static is not a tone!) • Interference demo – we are going to produce a tone from the speakers in the back of the room. They are about 1 meter apart. What do you hear as we slowly step back from the speakers? • Resonance - http://archive.org/details/SF121 • We are going over your quiz now – answers are on the board. Self check; then see a teacher for ay help you may need. When you are done, FINISH the Ch 26 Notes set 2! CHECK IN at stop signs and GET THE HELP YOU NEED! (stopping 5 minutes before the bell for a clicker exit)

31. All versions: Homework & math : See Board • B • B • A • A • B • B

32. Constructive Interference • When is it a good thing? • When is it a bad thing?

33. Destructive Interference • When is it a good thing? • When is it a bad thing?

34. Both waves have the same speed in the same medium. Use a ruler to answer the following…Which wave has the greater amplitude? • A • B • Same • Not sure

35. Both waves have the same speed in the same medium. Use a ruler to answer the following…Which wave has the greater wavelength? • A • B • Same • Not sure

36. Both waves have the same speed in the same medium. Use a ruler to answer the following…Which wave has the greater frequency? • A • B • Same • Not sure

37. Both waves have the same speed in the same medium. Use a ruler to answer the following…Which wave has the greater period? • A • B • Same • Not sure

38. Shown to the right are 2 different pairs of transverse wave pulses that move toward each other. At some point in time the pulses meet and interact (interfere) with each other.Which results in a larger AMPLITUDE when they meet? • A • B • Same • Not sure

39. Shown to the right are 2 different pairs of transverse wave pulses that move toward each other. At some point in time the pulses meet and interact (interfere) with each other.Which results in CONSTRUCTIVE interference? • A • B • Same • Not sure

40. Shown to the right are 2 different pairs of transverse wave pulses that move toward each other. At some point in time the pulses meet and interact (interfere) with each other.Which results in DESTRUCTIVE interference? • A • B • Same • Not sure

41. 26.10 Beats – not on test • Ever been next to a LOUD fan/engine, and hummed? • Beats are rapid changes in the loudness/ intensity of a sound when two tones very close in frequency are heard together. • They interfere with one another! • The diagram illustrates the wave interference pattern resulting from two waves (drawn in red and blue) with very similar frequencies.

42. A beat pattern happens when WAVE amplitude changes at a regular rate. The beat pattern (drawn in green) repeatedly oscillates from zero amplitude to a large amplitude Points of constructive interference (C.I.) and destructive interference (D.I.) are labeled on the diagram. When constructive interference occurs between two crests or two troughs, a loud sound is heard. This corresponds to a peak on the beat pattern (drawn in green).

43. When destructive interference (DI) between a crest and a trough occurs, no sound is heard • Amplitude relates to volume… so this beat pattern would be consistent with a wave which varies in volume at a regular rate. • A piano tuner utilizes beats to tune a piano string. • She will pluck the string and tap a tuning fork at the same time. If the two sound sources - the piano string and the tuning fork - produce detectable beats then their frequencies are not identical. • She will then adjust the tension of the piano string and repeat the process until the beats can no longer be heard. • As the piano string becomes more in tune with the tuning fork, the beat frequency will be reduced and approach 0 Hz. • SUPPOSE in this process, the piano is tuned at 496 Hz and the fork is 494 Hz. What will be the beat frequency? • 496-494 = 2 Hz • No beats = same frequency! (496-496 = 0!)