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Sound Waves and Echos: Understanding Distances and Frequencies in Room Temperature Air

In this lesson, students will dive into the principles of sound waves and their behavior in room temperature air. They'll explore how echo distances can be calculated using the speed of sound, examine the wavelength and frequency of sound waves, and determine whether humans and dogs can hear different sound frequencies. Students will engage in practical problems, access additional resources with a homework pass, and reflect on their understanding of sound concepts. Join us to enhance your auditory knowledge and tackle engaging sound-related challenges!

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Sound Waves and Echos: Understanding Distances and Frequencies in Room Temperature Air

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  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!)

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