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/*
* Copyright 1997 Phil Burk, Mobileer Inc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.jsyn.unitgen;
import com.jsyn.ports.UnitInputPort;
import com.jsyn.ports.UnitOutputPort;
import com.jsyn.util.PseudoRandom;
/**
* BrownNoise unit. This unit uses a pseudo-random number generator to produce a noise related to
* Brownian Motion. A DC blocker is used to prevent runaway drift.
*
* <pre>
* <code>
* output = (previous * (1.0 - damping)) + (random * amplitude)
* </code>
* </pre>
*
* The output drifts quite a bit and will generally exceed the range of +/1 amplitude.
*
* @author (C) 1997-2011 Phil Burk, Mobileer Inc
* @see WhiteNoise
* @see RedNoise
* @see PinkNoise
*/
public class BrownNoise extends UnitGenerator implements UnitSource {
private PseudoRandom randomNum;
/** Increasing the damping will effectively increase the cutoff
* frequency of a high pass filter that is used to block DC bias.
* Warning: setting this too close to zero can result in very large output values.
*/
public UnitInputPort damping;
public UnitInputPort amplitude;
public UnitOutputPort output;
private double previous;
public BrownNoise() {
randomNum = new PseudoRandom();
addPort(damping = new UnitInputPort("Damping"));
damping.setup(0.0001, 0.01, 0.1);
addPort(amplitude = new UnitInputPort("Amplitude", UnitOscillator.DEFAULT_AMPLITUDE));
addPort(output = new UnitOutputPort("Output"));
}
@Override
public void generate(int start, int limit) {
double[] amplitudes = amplitude.getValues();
double[] outputs = output.getValues();
double damper = 1.0 - damping.getValues()[0];
for (int i = start; i < limit; i++) {
double r = randomNum.nextRandomDouble() * amplitudes[i];
outputs[i] = previous = (damper * previous) + r;
}
}
@Override
public UnitOutputPort getOutput() {
return output;
}
}
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