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Instrument Control: Sensing and Control

follow

  kr      follow     asig, idt

Description

Envelope follower unit generator.

Initialization

idt – This is the period, in seconds, that the average amplitude of asig is reported. If the frequency of asig is low then idt must be large (more than half the period of asig )

Performance

asig – This is the signal from which to extract the envelope.

Example

  k1      line      0, p3, 30000    ; Make k1 a simple envelope
  a1      oscil     k1, 1000, 1     ; Make a simple signal using k1
  ak1     follow    a1, .02         ; ak1 is now like k1
  a2      oscil     ak1, 1000, 1    ; Make a simple signal using ak1
          out       a2              ; Both a1 and a2 are the same

To avoid zipper noise, by discontinuities produced from complex envelope tracking, a lowpass filter could be used, to smooth the estimated envelope.

Author

Paris Smaragdis
MIT, Cambridge
1995


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Instrument Control: Sensing and Control