2019-06-14

digital signal processing

"signals processed in this manner are a sequence of numbers that represent samples of a continuous variable in a domain such as time, space, or frequency"

facets of what i deem important knowledge for sound creation

links

subtopics

digital sound representation

a common format for storing signals digitally is sample values of the magnitude of a vibration over time, like discrete positions of a membrane between two bounding values

sampling rate

  • also called sample rate
  • describes how many samples represent one second of sound
  • with a higher sampling rate, more and higher frequencies can be represented
  • the maximum representable frequency in hertz is half the sampling rate, as any higher frequency than that would be spaced in a smaller duration than two subsequent sample values could represent

algorithms

  • stateless: need only parameter values that need not be kept
  • stateful: need parameters for values that need to be kept between function calls. for example, carryover values that fall outside the currently processed range
  • processing one input sample to one output sample: can affect multiple samples only with state and delay after accumulating samples
  • segment to segment: processors might depend on preceding or following values
  • one to many: output creates a longer signal
  • many to one: a longer signal becomes a shorter one

digital music making tools

  • analog hardware devices for synthesizers with keyboards or sequencing
  • software sequencers where instruments, synthesiser sounds, recordings and effects can be layed out and played back
  • software environments like fruity loops, reaktor, reason and others
  • lv2 or vst plugins as effects and synthesisers
  • taking audio recordings and prepare their ordered playback in a program like ardour or cubase
  • connecting hardware devices with midi and puredata and the user interfaces that it can create
  • preparing sample arrays using a general purpose programming language and writing to sound files

other

  • harmonic: a harmonic is a wave with a frequency that is a positive integer multiple of the frequency of the original wave
  • time series: a series of data points indexed (or listed or graphed) in time order. most commonly, a time series is a sequence taken at successive equally spaced points in time
  • a sound program is a potential for sounds to occur. elements can appear and disappear like entering and exiting a dimension. there is always some kind of seed, for example the literal arguments in program code
  • amplitude: the magnitude of the difference between a variables extreme values. the amplitude of a periodic variable is a measure of its change over a single period
  • clipping: limiting values to a maximum
  • digital image processing is a subcategory of digital signal processing
  • envelope: a path of loudness transition
  • every linear time-invariant system can be represented by a convolution
  • frequency: number of occurrences of a repeating event per unit time
  • low frequency: less change between samples
  • phase: relative shift or progression of a repeating event
  • sequencer: lays out the starting points and durations of sounds
  • vocoder: splits into frequency bands and removes bands
  • wave < instrument < composition. interval, duration, song or note relative offset