Basic Computer 101 and Basic Digital Audio

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Basic Computer 101 and Basic Digital Audio

• basic is a relative term

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Listening

• Paul Lansky, Smalltalk (1988, available on CD of
  same title, New Albion NA 030 CD)
• Otto Luening, Low Speed (1952, available on OHM
  Early Gurus of Electronic Music, in Bracken
  Library)

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Reading Discussion
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Operating Systems (OS)

• Handles basic tasks, like how hardware parts
  communicate with each other, defines how the user
  interacts with the computer, how software
  communicates with the computer, etc.
• Most OSs are extendable in function, meaning
  that functionality can be added to the OS through
  additional code.
• Extensions (Mac OS 9)
• Libraries (Windows dll, Mac OS X)
• Drivers (really libraries) usually add
  functionality for specific hardware devices
  (printers, audio interfaces)

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OS in depth (one slide)

• Kernel central core of the OS. It is the first
  to load during system startup (booting), and
  remains loaded throughout.
• Kernel space is separate from user space.
• Computer crash is a kernel crash.
• Programs (applications) run in user space. If a
  program crashes, the kernel (and hence, computer)
  can continue to run, as long the program wasnt
  interacting with the kernel is some crucial way.
• Geek Link http//www.bellevuelinux.org/kernel.htm
  l

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Multi-user file systems

• Mac OS X and Windows XP are multi-user OSs.
• Each user account has a specific folder or
  directory for storing data. (home directory)
• Each user account has specific access permissions
  to their own folders and other folders on the
  computer.
• The musicTech studios make use of a shared
  student account for easier system administration.

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Digital Audio
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Audio

• Physical properties (things that can be
  physically measured).
• Realm of Acoustics
• Perceptual properties (how humans perceive
  physical properties)
• Psychoacoustics

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Physical Properties

• Frequency
• Amplitude
• Spectrum, or spectral content
• All properties can change over time, as a
  function of time. That function is usually
  referred to as the propertys envelope.

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Perceptual Properties

• Pitch (frequency)
• Loudness (amplitude)
• Timbre (spectrum)
• Envelopes can still apply.
• The relationship of physical scales of
  measurement to perceptual scales of measurement
  is logarithmic.

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Analog Recording/Playback

• Analog recording/playback involves the
  transduction of air pressure fluctuations into
  corresponding electrical fluctuations.
• Electrical fluctuations are transduced into
  corresponding magnetic fluctuations for
  recording.
• Signal Chain Sound wave gt microphone gt
  electrical signal gt tape deck gt magnetic signal gt
  recorded on tape gt playback gt magnetic signal gt
  electrical signal gt amplifier gt speaker gt sound
  wave

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Digital Recording/Playback

• Digital recording/playback involves the
  conversion of electrical impulses into a series
  of numbers, or samples.
• The samples can be stored magnetically,
  optically, or in any way that can represent ones
  and zeros. (Binary numbers)
• Signal Chain Sound wave gt mic gt electrical
  signal gt Analog-to-Digital Converter (ADC) gt
  storage gt Digital-to-Analog Converter (DAC) gt
  electrical signal gt amplifier gt speaker gt sound
  wave

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Recording Quality

• Analog quality depends on transduction quality
  at every step of the chain.
• Copying requires additional transduction,
  creating some degradation. (generational loss)
• Digital quality depends on quality of ADC/DAC,
  and especially sample rate and bit resolution.
• Copying doesnt create any loss, as the system
  only has to detect the difference between a one
  and a zero.

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Binary Numbers (base 2)

• Every counting system has a base, or the rate at
  which digits or added.
• Our base 10 system means that there or ten digits
  possible for any place (0 - 9).
• Base 2, or binary, uses only two digits per
  place, 0 and 1. (switches)
• Each binary place is a bit. (binary digit)
• Any counting system can be converted to a base 10
  number by multiplying each digit by the base to
  the power of the digits place. You count places
  starting at zero. (ex.)
• Going from base 10 to binary requires that you
  know the powers of 2. (ex.)

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Reading Assignment

• Roads, Chapter 1. Due 1/24