(8.D.1.2) RandiFract32
Overview
Low frequency noise generator
Discussion
Generates slowly varying random noise using by linearly interpolating between random values. The underlying random noise lies in the range [-1 +1). The module computes a new random value at the rate specified by .freq. If isSmoothed = 1, then linear interpolation is used between values. If isSmoothed = 0, then the output changes instantly effectively generating a square wave with constant period but random amplitudes.
Internally, the module uses a 32-bit linear congruential generator to generate random values. The initial seed of the random number generator is specified by .seed. If .fixCurrentSeed is 1, then the seed is fixed. This means that the prebuild function will not generate a new seed. By default, .fixCurrentSeed equals 0, and thus instances of the generator will produce different outputs.
Type Definition
typedef struct _ModuleRandiFract32
{
ModuleInstanceDescriptor instance; // Common Audio Weaver module instance structure
FLOAT32 freq; // Rate at which random values are generated.
INT32 isSmoothed; // Determines whether the random signal interpolates between random values (isSmoothed=1) or steps between random values (isSmoothed=0).
fract32 slope; // Slope value for linear interpolation between random values.
fract32 level; // The current value of the random signal.
INT32 rate; // Starting value for counter, dependent on freq.
UINT32 seed; // State of the random number generator.
INT32 fixCurrentSeed; // Whether the prebuild function resets the seed or not. 0 = reset, 1 = no reset.
INT32 counter; // Counter value is used in slewing between random values.
fract32 oneOverRate; // Used in calculating the slope value.
} ModuleRandiFract32Class;
Variables
Properties
Name | Type | Usage | isHidden | Default value | Range | Units |
freq | float | parameter | 0 | 1000 | 0.01:24000 | Hz |
isSmoothed | int | parameter | 0 | 1 | 0:1 | Â |
slope | fract32 | state | 0 | random value | Unrestricted | Â |
level | fract32 | state | 0 | 0 | Unrestricted | Â |
rate | int | state | 0 | 48 | Unrestricted | Â |
seed | uint | state | 0 | random value | Unrestricted | Â |
fixCurrentSeed | int | parameter | 0 | 0 | 0:1 | Â |
counter | int | state | 1 | 48 | Unrestricted | Â |
oneOverRate | fract32 | derived | 1 | 0.02083 | Unrestricted | Â |
Pins
Output Pins
Name: out
Description: audio output
Data type: fract32
MATLAB Usage
File Name: randi_fract32_module.m
M=randi_fract32_module(NAME, SR, BLOCKSIZE)
Creates a slowly varying random generator based on linear interpolation.
This module has a single 1 channel output pin with controllable
frequency. The output of the module changes instantly when the
frequency is updated. Fract32 version
Arguments:
NAME - name of the module.
SR - sample rate.
BLOCKSIZE - number of samples per output channel.
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