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Signal Generators: Random (Noise) Generators

x-class noise generators

  ir      linrand    krange 
  ir      linrand    krange
  kr      linrand    krange
  ar      linrand    krange

  ir      trirand    krange
  kr      trirand    krange
  ar      trirand    krange
  
  ir      exprand    krange
  kr      exprand    krange
  ar      exprand    krange

  ir      bexprnd    krange
  kr      bexprnd    krange
  ar      bexprnd    krange

  ir      cauchy     kalpha
  kr      cauchy     kalpha
  ar      cauchy     kalpha

  ir      pcauchy    kalpha
  kr      pcauchy    kalpha
  ar      pcauchy    kalpha

  ir      poisson    klambda
  kr      poisson    klambda
  ar      poisson    klambda

  ir      gauss      krange
  kr      gauss      krange
  ar      gauss      krange

  ir      weibull    ksigma, ktau
  kr      weibull    ksigma, ktau
  ar      weibull    ksigma, ktau

  ir      betarand   krange, kalpha, kbeta
  kr      betarand   krange, kalpha, kbeta
  ar      betarand   krange, kalpha, kbeta

  ir      unirand    krange
  kr      unirand    krange
  ar      unirand    krange

Description

All of the following opcodes operate in i-, k- and a-rate.

linrand krange – Linear distribution random number generator. krange is the range of the random numbers (0 - krange). Outputs only positive numbers.

trirand krange – Same as above only outputs both negative and positive numbers.

exprand krange – Exponential distribution random number generator. krange is the range of the random numbers (0 - krange). Outputs only positive numbers.

bexprnd krange – Same as above, only extends to negative numbers too with an exponential distribution.

cauchy kalpha -Cauchy distribution random number generator. kalpha controls the spread from zero (big kalpha = big spread). Outputs both positive and negative numbers.

pcauchy kalpha – Same as above, outputs positive numbers only.

poisson klambda – Poisson distribution random number generator. klambda is the mean of the distribution. Outputs only positive numbers.

gauss krange – Gaussian distribution random number generator. krange is the range of the random numbers (-krange – 0 - krange). Outputs both positive and negative numbers.

weibull ksigma, ktau – Weibull distribution random number generator. ksigma scales the spread of the distribution and ktau, if greater than one numbers near ksigma are favored, if smaller than one small values are favored and if t equals 1 the distribution is exponential. Outputs only positive numbers.

betarand krange, kalpha, kbeta – Beta distribution random number generator. krange is the range of the random numbers (0 - krange). If kalpha is smaller than one, smaller values favor values near 0. If kbeta is smaller than one, smaller values favor values near krange. If both kalpha and kbeta equal one we have uniform distribution. If both kalpha and kbeta are greater than one we have a sort of Gaussian distribution. Outputs only positive numbers.

unirand krange – Uniform distribution random number generator. krange is the range of the random numbers (0 - krange).

For more detailed explanation of these distributions, see:

  1. C. Dodge - T.A. Jerse 1985. Computer music. Schirmer books. pp.265 - 286
  2. D. Lorrain. A panoply of stochastic cannons. In C. Roads, ed. 1989. Music machine . Cambridge, Massachusetts: MIT press, pp. 351 - 379.

Example

a1  trirand    32000         ; Audio noise with triangle distribution
k1  cauchy     10000         ; Control noise with Cauchy dist.
i1  betarand   30000, .5, .5 ; i-time random value, beta dist.

Deprecated Names

These opcode names originally started with i, k, or a to denote the rate at which the opcode operated. These names are deprecated as of Csound version 3.49. The current form should now be used; the previous form will not work.

Author

Paris Smaragdis
MIT, Cambridge
1995


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Signal Generators: Random (Noise) Generators