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Karteikarten

Acoustics

Nader Attalla ACOU Englisch 68 Karten

Karten in diesem Stapel (68)

  1. 1What is the Fourier Theoremany complex waveform can be broken down into x number of sine components, each of different frequency, amplitude and phase
  2. 2What is traverse wave motiona wave in which the particle motion is perpendicular to the direction of wave motion
    ie. how waves in water move
  3. 3What is longitudinal wave motiona wave in which the partial motion is in the same direction, or parallel as the wave motion
    ie. how sound moves
  4. 4What is superpositionwhen two waveforms in the same place, create a new wave by summing the individual waves
  5. 5What is constructive/positive interferencerelating to superposition it is when two waves are in phase and they increase in amplitude
  6. 6What is destructive/negative interferencerelating to superposition it is when two waves are out of phase and they cancel each other out
  7. 7What is a complex wavea wave that has more then one frequency, the result of multiple sine waves added together
  8. 8what is phase shiftterm used to describe one waveforms relationship/location to another and whether they are "in phase" (matching phase angle) or "out of phase" (don't have matching phase angle)
  9. 9what is phase anglephysical point on a cycle measured in degrees (one complete cycle = one complete circle)
  10. 10What is attackthe initial "hit" of a certain sound otherwise known as the transient
  11. 11What is decaythe lowering in amplitude from the initial attack to sustain
  12. 12What is sustainthe longest part of a note that occurs between the decay and the final release
  13. 13What is releasethe final part of a note that ends the sound to the zero point
  14. 14What is the ADSR envelopeattack, decay, sustain and release
  15. 15What is timbrethe individual sound that an instrument makes
    ie. a violin and guitar both play a "c note but each have their own timbre
  16. 16What is a chordophonean instrument that creates it's sound from stretched strings
  17. 17What is a membranophonean instrument that makes it's sound from a stretched membrane
  18. 18What is a aerophonean instrument that uses wind through a column to create sound
  19. 19What is an idiophonean instrument that is made of a naturally resonating/sonorous material
    ie. wood, metal
  20. 20What is the missing fundamental effectthe phenomena that occurs inside the human ear that can perceive certain sounds (ie. bass) even if it is not present (300hz, 400hz, 500hz present = a perceived frequency of 100 hz)
  21. 21What are harmonically related modes of vibrationan instrument that produces a clear defined pitch consisting of whole number multiples of the fundamental sound
    ie. guitar
  22. 22What is the fundamental frequencylowest frequency a vibrating element can vibrate at, also the loudest sound that will be heard when multiples frequencies are played
  23. 23What is the mode of vibrationterm used to describe the way a structure vibrates, also known as degrees of freedom. sum of total modes = complex wave
  24. 24What are the three things all instruments consist ofattack device (pick), vibrating element (string), resonator (guitar body)
  25. 25What is Beat Frequencies?when two waves are close in frequency the resultant sound wave will create a beat at the frequency equal to the absolute difference
  26. 26What are Harmonically Related Modes of Vibration?modes that are whole number multiples of the fundamental
  27. 27What is a nodes and antinodes?Node= zero amplitude point on the wave
    Antinode=max. amplitude point on the wave
  28. 282 waves, different phase angle, different amp, different frequencies when added together results in?a complex wave (multiple frequency components)
  29. 29Explain the antinodes and node of a longitudinal wave+ antinode = compression
    - antinode = rarefaction
    node = atmospheric pressure
  30. 30P.O.E. ?Point of equilibrium aka the system is at rest
  31. 31What is frequency (f) ?the number of cycles per second (Hz)
  32. 32what is wavelength (lambda) ?physical length in feet or metres / total distance for 1 cycle
  33. 33what is period (t) ?time for 1 cycle, t=1/f
  34. 34what is the wave equation?Velocity= frequency x wavelength
  35. 35what happens to the wavelength when the frequency increases?wavelength decreases
  36. 36what has more energy and travels farther Lf or Hf?Lf
  37. 37Damping resistance?forces which remove energy from the system and to stop vibration
  38. 38Decay envelope?the time it takes to make the waveform stop vibrating
  39. 39when damping forces are acting on a waveform what changes the amplitude or frequency?only amplitude changes
  40. 40What is resonant frequency?the frequency a system wants to naturally vibrate at
  41. 41What are some factors that make resonant f unique to eat system?mass, density and the forces involved
  42. 42What is sympathetic vibration?when a f equal to the resonant f of the system, causing the system to vibrate and exhibit n increase in amplitude
  43. 43what does the velocity of sound depend on?1.the medium in which is travels (density and elasticity) the less dense/ more elastic, the fast the sound will travel
    2.Temperature
  44. 44What is the velocity of sound through air?344m/s or 1130ft/s at 20 C
  45. 45for example, when climbing up a mountain how does velocity of sound through air change?+0.6m/s for every +1 degree
  46. 46what is acoustics?a branch of science that deals with production, control, transmission, reception and effects of sound
  47. 47what is reverberation?sound that bounces of walls/reflective surfaces
  48. 48what is sound?disturbance or a vibration in a medium that causes auditory sensation within the ear
  49. 49what three things are needed for a sound to occur?1. something to cause a vibration
    2. a medium
    3. an ear or brain to perceive sound
  50. 50What is anechoic?no reverberation, no sound reflects back at you
  51. 51what is reflection?when sound travels through a medium encounters a boundary it will "bounce off"
  52. 52What is Specular reflection?results from smooth surfaces, angle of incidence is equal to the angle of reflection
  53. 53what is diffusion?reflection on irregular surface geometry, the result is numerous smaller waves with reduced energy (1 wave in, bunch of a smaller waves out)
  54. 54what is refraction?a wave travelling from one medium to another will undergo a change of direction. the change of direction is a result of the change in speed do to the change of mediums. frequency is constant, but velocity and wavelength changes
  55. 55explain refraction due to temperature change in air?during the day, surface of earth is warmer then atmosphere so sound travels towards the atmosphere and opposite for the night time.
  56. 56what is diffraction?when sound waves encounter an obstacle they tend to bend around it. although LF bends a lot easier then HF
  57. 57What is transmission?when sounds encounter a boundary some of the engird can pass through it. LF= more energy = more transmission. boundary becomes a vibrating element
  58. 58the amount of transmission depends on what?the boundaries mass, density and the rigidity (stiffness)
  59. 59What is absorption?the process by which sound energy is diminished upon contact with a boundary , determined by the properties of the material
  60. 60What is a wavefront?lines of constant pressure forming a continuous surface which moves with time. Acts like a sphere/bubble. LF propagates as a wavefront
  61. 61Wavefronts predominately display which properties? (specular reflection, refraction, diffusion, diffraction, transmission, absorption)diffraction, transmission, refraction
  62. 62What is a ray?a point traveling in s straight line over time in the direction of wave motion. They are all perpendicular to the wavefronts. HF propagates as a ray
  63. 63Rays predominately display which properties? (specular reflection, refraction, diffusion, diffraction, transmission, absorption)specular reflection, diffusion, absorption
  64. 64If the frequency decreases how do the HF rays change?comes more like a cone shape. Lower frequencies = less directional
  65. 65What is inverse square law?the intensity of sound is inversely proportional to the square of the distance from the source
    (ex. at 3 times the distance the sound intensity is 1/9 sound energy)
  66. 66What is the inverse square law equation?I = 1/d^2
  67. 67What is Doppler Shift?a change in apparent frequency due to motion of observer or source. if source is moving towards observer, the frequency seems to increases and vice versa.
  68. 68in terms of doppler shift, if the velocity of the object matches the speed of the wave what results?a sound barrier

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Beschreibung
ACOU Karteikarten am Acoustics, erstellt von Nader Attalla am 10/10/2016.
Erstellt von
Nader Attalla
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3
Verlauf
  • Erstellt von Alex Meulenbeld · 25 Sep 2016
  • Kopiert von Kaleb Vernon · 26 Sep 2016
  • Kopiert von Nader Attalla · 10 Okt 2016
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