SLHS 2010 Exam 2 Study Guide
SLHS 2010 Exam 2 Study Guide SLSH 2010 001
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This 7 page Study Guide was uploaded by Alexandra Funk on Wednesday March 16, 2016. The Study Guide belongs to SLSH 2010 001 at University of Colorado at Boulder taught by Ryan Pollard, Ph.D. CCC-SLP in Spring 2016. Since its upload, it has received 50 views. For similar materials see Science of Human Communication in Linguistics and Speech Pathology at University of Colorado at Boulder.
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Date Created: 03/16/16
Exam 2 Study Guide 1. How do we define sound? Physical properties: defines the physical and mathematical properties of sound Perceptual properties: defines the way in which we perceive sounds – based on human perception 2. What is Simple Harmonic Motion? How do the examples (pendulum, mass on a spring, tuning fork, vibration of an air mass) illustrate SHM? A repeating motionThe simplest vibratory motion is Simple Harmonic Motion Harmonicrepeating motion Simplerestoring force proportional to displacement Each of the example move in a repeated motion o Pendulum: a mass on the end of a string, moves back and forth o Mass on a spring: up and down o Tuning Fork: vibrations back and forth between the prongs. o An Air Mass: energy transmitted by the vibration of the surrounding medium. All of the following are restored to a position proportional to displacement until acted upon by another force (such as gravity, or friction) 3. Be able to describe the concepts from physics related to SHM. A. Inertia Resistance of any physical object to any change in its state of motion (including a change in direction) B. Potential Energy the energy due to the position of the body or the arrangement of the particles of the system – usually associated with restoring forces C. Kinetic Energy Energy due to its motion D. Velocity Rate of change of displacement Velocity (speed) is the displacement divided by the time – D/t Units m/s E. Gravity Force with which all physical bodies attract each other The thing that gives weight to physical objects, and causes physical objects to fall toward the ground when dropped from a height F. Cycle the pendulum’s movement from rest to maximum displacement in one direction, back through rest to maximum displacement in the other direction, and back to rest. G. Elasticity The property of an object or material which causes it to be restored to its original shape after distortion ∙ It is said to be more elastic if it restores itself more precisely to its original configuration H. Newton’s First Law of Motion An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an external force. (seat belt law) I. Hooke’s Law The magnitude of the restoring force (elasticity) is proportional to the displacement from rest. 4. How does SHM explain sound? What are compressions & rarefactions? A compression is a high pressure region with molecules close together. Low pressure area is called rarefactions SHM explains sound because it is a repeating pattern in which air molecule are moved by the pressure of the wave, and it moves in a wavelike pattern 5. What are the two requirements for sound? Vibration of an object (source) Energy carried through the air (medium) 6. These two requirements BOTH have the same two features necessary for sound. What are they? Sound must have a source Sound must have a medium 7. Can sound be transmitted in Outer Space? NO, there’s no medium for it to be transferred through 8. What is the difference between Transverse Waves, Longitudinal Waves, and Surface Waves? Which of these wave types is sound? Transverse Waves: a wave in which the particles of the medium are displaced in a direction perpendicular to the direction of energy transport Longitudinal Waves: a wave in which particles of the medium move in a direction parallel to the direction which the wave moves Surface Waves: a wave in which the particles of the medium undergo a circular motion 9. What is the Waveform? What information is represented in the typical waveform? An illustration of a sound wave. Typically represented by amplitude and time period. 10. What is frequency? What are the units of frequency? What is the difference between high frequency & low frequency? Frequency: ratio of how many times we complete some action to the time it takes for it The units of frequency are Hertz (Hz) The difference between high frequency and low frequency is that: If one wave has more cycles per second than another, then it has a higher frequency If one wave has fewer cycles per second than another, then it has a lower frequency 11. What range of frequencies is relevant for human hearing? 20 to 20,000 Hz 12. What is an octave? How would you calculate one octave above a reference frequency? One octave below a reference frequency? How would you calculate more than one octave change from a reference frequency? Octave: is the interval between two points where the frequency at the second point is twice the frequency of the first. An octave above a reference frequency N signifies the number of octaves above or below F octave = Fb x 2^n One octave below a reference frequency F octave = Fb x 2^n 13. What is the Spectrum, or Frequency Line Spectrum? What information is represented in this graph? → Represents the frequency of a sound wave, represented by Amplitude and frequency (Hz) 14. What is the definition of a Period? How is it calculated? What is the relationship between seconds and milliseconds? Period: How much time it took to complete one cycle ∙ T = 1/F ∙ The relationship between seconds and milliseconds is that 1 second is 1,000 milliseconds 15. What is the definition of a Wavelength? How is it calculated? ∙ Speed of sound (c) divided by the frequency (f) ∙ Wavelength (λ) is inversely proportional to frequency λ= c/f λ is the wavelength in meters c is the speed of sound in m/s f is the frequency of the sound in Hz 16. How does temperature affect the speed of sound? Why? ∙ For every 1°C increase above 0°C, the speed increases by 0.6 m/s • Ex: What is the speed of sound at room temperature (21.1°C)? Adjust for temperature – c = 331.4 m/s + (0.6 × 21.1) – c = 331.4 m/s + 12.66 – c = 344.1 m/s at room temperature 17. What is Amplitude? What is Displacement? Amplitude tells us how far and in what direction the particles in a medium have been displaced Displacement: Change in position The distance from a reference (starting position – equilibrium) Describes both distance and direction 18. What is Instantaneous Amplitude? How is it measured? ∙ The magnitude of displacement, relative to the magnitude at equilibrium, for any given point of time during a wave ∙ Measured by time 19. What is Peak Amplitude? How is it measured? ∙ The magnitude at the point of maximum displacement relative to the magnitude at equilibrium 20. What is PeaktoPeak Amplitude? How is it measured? ∙ The difference in magnitude of displacement between two oppositevalence peak points in a wave ∙ Absolute difference between a positive peak and a negative peak 21. What is Root Mean Square (RMS) Amplitude? How is it measured? RMS is a statistical measure of the magnitude of a varying wave Average of instantaneous amplitudes over a range of time values Also called the quadratic mean 23. What is force? What is pressure? Which is most useful for measuring sound? What is the basic unit of that measure? ∙ Force: can be thought of as any push or pull applied to an object ∙ (most useful for measuring sound) Pressure: Force per Unit Area Force/ Area Remember Elephant (Elephant on triangular rather than rectangular object contained more pressure) 24. What is the reference point for measuring sound amplitude? What is the definition, and what is the actual value? What is the range of human hearing using that measurement? 0.0002 dynes/cm^2 is the reference point used (The absolute pressure level of the smallest sound humans can hear) Range of human hearing: 0.0002 dynes/cm^2 to 200 dynes/cm^2 25. What is the Decibel? What is the observed pressure? What is the reference pressure? Decibel: Relative difference in sound pressure between two sounds Observed Pressure Po, Reference pressure Pr (0.0002) 25. What is the formula for calculating Decibels? What two features of this formula make it useful for measuring sound? dB SPL=20xlog(Po/Pr) Logarithmic scale (which reduces the range of human sensitivity to a manageable scale) and ratio scale (compares sound pressure to a reference value, scale starts at 0 for humans) make it useful for measuring sound 27. How do we calculate the decibel value of two sounds added together? Essentially convert all (given) decibels to dynes (if not given in dynes) add the dynes together and then convert back to dB SPL 28. How can you calculate pressure from a dB value? Using the same formula for decibels dB SPL=20xlog(Po/Pr) but plug in the dB value (and reference value) and work backwards 29. What is Damping? How does it affect amplitude? How does it affect frequency? How can we measure damping? Damping is a decrease in amplitude Friction opposes motion which causes a decrease in vibrating over time and thus damping Damping is the inverse of amplitude; measured by taking 20log(n) where n is the ratio of the speakers (one person one meter away and another person three meters away is ⅓) and adding it to the original amplitude heard by the first person 30. What is phase? How is it measured? How does the clock figure in? The location of a point in the cycle Measured by finding starting point (at 0 going up 0 degree phase, positive going down 90 degrees phase, 0 going down 180 degrees phase, negative going up 270 degrees phase) Clock figured in because it moves in a like circular motion if the pattern is periodic 31. What are the three main properties of a sound wave? Frequency, amplitude, phase 32. What is the difference between a simple wave and a complex wave? How are complex waves formed? Simple waves: one frequency component. Complex wave: more than one frequency component. Complex waves are formed when frequencies are combined. 33. What is interference? What is the difference between constructive and destructive interference? Interference: combining waves. Constructive interference: when two sounds interfere add and result in a higher amplitude. (addition) Destructive interference: when two sounds add and result in a lesser amplitude. (Difference) 34. What is a Complex Harmonic Wave? What is the fundamental frequency? What are the harmonics? What determines the overall pattern of a complex harmonic wave? A complex harmonic wave repeats at the rate of the fundamental frequency, and harmonic components are visible. Complex harmonic waves are periodic 35. How can you tell if a complex wave is periodic? •Periodic waves repeat over and over, if you have a complex harmonic wave, it will be periodic. 36. What information is conveyed in a Spectrogram? What information is missing? How is it related to the Spectrum The frequency and time of a sound wave is conveyed in this graph. The amplitude of the wave is missing and this is related to the spectrum because it tells us how far and in what direction the particles in a medium have been displaced 37. What is a Fourier series? → It is complex wave in which all the frequency components are related 38. What are the Square Wave, Triangle Wave, and Sawtooth Wave? Which of these is most relevant to speech, and why? These are types of complex harmonic waves. Sawtooth wave is most relevant to speech because it is closest to the vocal source. 39. What is the definition of Resonance? → is defined as the increase in amplitude. What is an object’s Preferred Frequency? → based on the object's physical characteristics. How does Resonance relate to Preferred Frequency? → resonance is the increase in amplitude that occurs when an object vibrates at its preferred frequency. 40. How does a child on a swing illustrate the concepts of Preferred Frequency and Resonance? → A child on a swing is essentially a pendulum. •It will vibrate at a frequency determined by its length. •An increase in amplitude is called resonance. 41. What is the difference between Mechanical Resonance and Acoustic Resonance? Mechanical resonance: If an external force is applied at the right time during a cycle, you can cause an increase in amplitude. Acoustic resonance: Air in a container (or cavity) resonates. •In both kinds, there is an increase in amplitude •In Mechanical, you need an external force at the right times •Only Acoustic involves a change in frequency of the output, more than one resonant frequency involved •Acoustics Resonance = change in amplitude + change in frequencies 42. For Acoustic Resonance, what determines the Preferred Frequency? The physical properties of the system (in this case the container) 43. What are the two consequences of Acoustic Resonance? Sound goes in quiet and comes out louder. Sound goes in as noise but comes out with a different frequency (filtered). 44. What is the difference between a Traveling Wave and a Standing Wave? A traveling wave is observed traveling through a medium, a crest is seen moving along from particle to particle. A standing wave is an interference phenomenon caused by sound reflection formed as the result of the perfectly timed interference of two waves passing through the same medium. 45. In terms of the sine wave, what are the Nodes? And what are the Antinodes? •Nodes are where there is no displacement of particles –Zero displacements –Mnemonic (To help remember the word): ([No de]splacement J) •Antinodes are where displacement is maximum 46. Why do we talk about a tube when talking about Acoustic Resonance? Flute, Oboe, Clarinet, Vocal Tract •The sound that resonates will have a wavelength that is proportional to the length of the tube 47. What feature of a sound matters for Tube Resonance? 48. What happens at a tube’s open end? What happens at a tube’s closed end? •At an open end, particles will be at high displacement where the tube opens up.We want a displacement antinode •At a closed end, displacement node at closed end, antinode at open end. 49. What is the difference between resonance in an Open Tube vs. a Closed Tube? Open tube resonance = 2x length of the tube Closed tube resonance = 4x length of the tube 50. What do filters do? The frequencies that don’t fit get filtered out. 51. What determines the Resonant Frequency of an Open Tube? What happens to Harmonics of that Resonant Frequency? Resonant frequency of an open tube = c/(2xLength of Tube) All harmonics are accounted for. x2,x3,x4,x5,x6…….. 52. What determines the Resonant Frequency of a Closed Tube (open at one end)? What happens to the Harmonics of that Resonant Frequency? Resonant frequency of a closed tube= c/(4xLength of Tube) Only the odd harmonics are accounted for. x3,x5,x7,x9…. 53. What does “Half Wave Resonator” mean? “Quarter Wave Resonator”? A closed tube has a Quarter Wave Resonator because the basic pattern that resonates in it seems like quarter of a wave An open tube has a half wave resonator because it has A frequency with wavelength that is half the length of the tube resonates in it. Be prepared for calculations related to: A. Octaves B. Period C. Wavelength D. dynes/cm à dB SPL E. dB SPL à dynes/cm 2 F. Adjusting amplitude G. Damping H. Resonant Frequencies
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