Intro To Audio

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Intro To Audio
2012-01-20 15:53:37
intro audio

Vocab terms and facts about Audio Recording
Show Answers:

  1. What does MTR stand for?
    Multi track Recorder
  2. What does SLS stand for?
    Studio Loud Speakers
  3. Doubling the intensity of a sound variation adds a gain of _____.
    3 dB
  4. What is Phase?
    A time delay between 2 or more waveforms
  5. How is Phase measured?
  6. What happens when 2 soundwaves are 180 degrees out of Phase?
    It cancels out the sound
  7. What is Hermonic Content?
    The way we differinciate between voicings, or tones.
  8. What are Partials and Harmonics?
    • Partials: Frequencies that exist in addition to the fundimental frequency. (AKA "overtones")
    • Harmonics: overtones that are whole number multiples of the fundimental freq.
    • Ex: So let's consider the note that's 440 Hz (which is the A above middle C, referred to as A4). The harmonic partials of this note are:

    • 440x1 = 440Hz (A4 -- the base note itself),
    • 440x2 = 880Hz (A5, an octave above),
    • 440x3 = 1320Hz (approx. the E6, the E above A5),
    • 440x4 = 1760Hz (A6, two octaves above A4),
  9. What are the 2 categories of waveforms?
    • simple: square, triangle and sawtooth waves. They're simple bc the have consistant harmonic structures, and they are continuous and repetitive.
    • complex: dont necessarily repeat (ex: basic speach, instruments)
  10. What is timbre?
    Also called "tonal balance", it is what makes a particular musical sound different from another, even when they have the same pitch and loudness. For instance, it is the difference between a guitar and a piano playing the same note at the same loudness.
  11. What is envelope?
    the characteristic variations in level that occur in time over the duration of a played note. They're broken up into four parts: Attack, Decay, Sustain, & Release.
  12. Define Attack.
    The time taken for a note to build up to its full volume, when the note is sounded.
  13. Define Decay.
    How quickly th sound levels off to a sustain level after the initial attack.
  14. Define Sustain.
    The duration of the ongoing sound that is generated, following the initial attack decay.
  15. Define Release.
    How quickly the sound will decay once the note is released.
  16. Define frequency. How is it measued?
    • How often and event occurs.
    • Measured in Hertz (Hz)
    • *Frequency has to do with pitch. The faster the frequency (or cycles per second), the higher the pitch.
  17. What is the range of human hearing?
    Human hearing generally falls between 20 to 20k Hz (or cycles per sec.)
  18. What are the characteristics of a wave form?
    • P.H.E.W. F.A.V.
    • Phase
    • Harmonic Content
    • Envelope
    • Wavelength
    • Frequency
    • Amplitude
    • Velocity
  19. What are the 4 types of waveforms?
    sine, square, triangle and sawtooth
  20. Define Amplitude. How is it measured?
    • the loudness/volume of sound
    • it is measured in decibels (dB)
  21. What is the range of human hearing in dB?
    0-120 dB
  22. What is a transducer? Give an example of one.
    any device that converts one form of energy to another. Ex: a windmill, ears, microphone, speakers
  23. What is Impedence? How is it represented?
    • a measure of the amount of opposition in an AC current.
    • represented by the letter Z (also shown as High-Z or Low-Z)
  24. List the various signal levels from lowest to highest.
    • 1. mic level
    • 2. instrument level
    • 3. line level
  25. What is frequency response?
    • a chart that shows the pitch response of a microphone or any sound capturing device
    • the x-axis shows the response in Hz, the y-axis show it in dB
  26. What is directional response?
    • the sensitivity of a mic's response at different angles.
    • the path is 3D and has 3 catagories: omnidirectional, bidirectional, and cardoid
  27. What is the proximity effect?
    a change in frequency response of a directional mic as the sound source gets closer to the mic. The result is an increase in bass.
  28. What is attenuation?
    Reduction of a sound in amplitude. Measured in negative decibels. Example: -3db is a 3 decibel reduction.
  29. Give some example of Timbre terms:
    Bright, Dark, Metallic, Warm, Tinny, Deep etc.
  30. Define Node:
    a stationary point in a mode of vibration
  31. Define Antinode:
    point of widest motion in a mode.
  32. What's the Spectrum of a sound?
    The Spectrum of a sound is the combination of frequencies that make up a complex timbre. Most often these are harmonics in various combinations and at various volumes.
  33. What is used to describe a: smaller number of unrelated frequencies, few enough to be heard individually?

    Bells, gongs, and most metal instruments make these sounds, as do drumheads...
    A non-harmonic spectrum
  34. What is Residue?
    Non harmonic and noise components of an otherwise harmonic spectrum. Breath, consonants, and air noise are examples.
  35. Define Resonance:
    the capacity of an object to emphasize certain frequencies while reducing others. A bottle has a resonant frequency.
  36. What's Formant:
    a resonance in an instrument or voice that does not change with pitch.
  37. What is comb filtering?
    When two copies of the same sound arrive at different times, either in a recording or in an actual space. If these two sounds are at similar levels and are within about 20 milliseconds of one another, a tonal coloration. The name is given because some frequencies will cancel and other frequencies between them will reinforce, forming a comb-shaped frequency response.

    The spacing of the "teeth" is based on the delay between the two sounds, and the depth of the dips is based on the similarity of the two signals' volumes. When the two waves are equal in level, the comb filtering is most intense.
  38. What are some causes of comb filtering?
    • 1. Two microphones at different distances picking up the same sound.
    • 2. A strong reflection off a hard boundary like a wall or floor.
    • 3. Multiple sound sources such as guitar cabinets all with the same source.
  39. Ways to minimize comb filtering:
    • 1. Observe a 3-to-1 microphone placement: One mic should be three times as far away from the source as another. This keeps the levels different enough to reduce comb effects.

    2. Keep microphones away from strong boundaries, and avoid a mic between a nearby boundary and the source.

    3. Avoid large numbers of speaker cabinets when recording guitar, and when possible mic one cone of the cabinet closely rather than putting the mic between cones.

    4. Learn to recognize comb filtering and move your mics around until the signal is free of this sound.
  40. What is distortion?
    • A term meaning a change in the waveshape of a sound, causing a change in timbre. Most distortion is undesirable and detracts from the quality of the sound.
    • *There are cases, however, where distortion imparts character and could be considered beneficial.
  41. What is Clipping?
    A type of distortion that occurs when a circuit cannot reproduce the highest amplitude signals due to a lack of headroom. Typically the tops of waveforms are flattened creating the characteristic “clipped” waveshape.

    In extreme cases the waveshape will look like a square or rectangle. The effect on the sound is to add harmonics that previously did not exist in the spectrum, causing a bright and buzzing sound. The nature of these harmonics is determined by the transfer function and symmetry of the clipping. Once a signal is clipped, it is very difficult or impossible to restore the recording.
  42. What is Digital clipping?
    This occurs when a signal exceeds the numeric limits of a digital system. This type of clipping is typically very harsh due to the unforgiving mathematical nature of the problem. Digital clipping will cause loud buzzing and popping sounds that usually render a recording unusable. Usually this type of distortion is symmetrical, leading to odd-numbered harmonics.
  43. What Soft and Hard clipping?
    Depending on their design, analog circuits can clip in a way that is not sudden, but gradual, leaving rounded rather than flat tops on the waveform. Likewise, the onset of clipping is gradual rather than sudden, so their is no sudden transition to clipping. This is known as soft clipping and is less intrusive than the hard clipping sounds produced by digital devices. This type of distortion in small doses can actually benefit certain sounds, adding character.

    Soft clipping is typical of tube and FET circuits.
  44. What happens when a device clips both the positive and negative sides of a waveform equally?
    Symetrical Distortion
  45. What happens to two signals that are unrelated frequencies are distorted together?
  46. What are the 3 ways to combat phase cancellation when you're stereo miking?
    Equidistance, coincident pairing, and the 3:1 rule
  47. When combating phase cancellation, what is equidistance?
    Ensuring the 2 (or more) mics are the same distance away from the source
  48. When combating phase cancellation, what is Coincident Pairing?
    Placing the mics so close that the sound emitting from the source should hit the mics' diaphrams at the same time.
  49. When combating phase cancellation, what is the 3:1 rule?
    Setting one mic 3x the distance from the other mic, in relation to the source.

    Ex: If mic A. is 2ft from the source, mic B. will be 6ft. (2ft x 3 = 6ft)
  50. Name the 5 stereo miking techniques:
    Spaced Pairing, XY Configuration, Blumlein Pairing, ORTF, & Mid-Side
  51. Describe the Space Pairing mic technique:
    2 cardoid mics placed apart from each other to produce 2 different recordings of the same instrument.
  52. Describe the XY configuration miking technique:
    2 cardoid mics placed with their heads together at 90 degree angles. The result is that one mic will pick up the front left & back right of the room, and the other will pick up the front right & back left of the room.
  53. Describe the Blumlein Pairing technique:
    similar to XY technique, however using 2 bi-directional mics at 90 degree angles.
  54. Describe the ORTF miking technique:
    A french made technique; also called a binaural technique which means its meant to approximate the response of your ears. Using 2 cardoid mics that are placed at a 110 degree angle w/the heads 7 in apart.
  55. Describe the Mid-Side miking technique:
    Placing one cardoid mic pointing at the source and a bi-directional mic placed perpendicular to the cardoid mic. They're both recorded onto one track. The track recorded with the bi-directional mic is copied and phase is inverted on the one copy. The 2 bi-directional tracks are then panned hard-left and hard-right, while the cardoid mic track is panned center.