Project #16: Sound – Brownian Noise – Mk02

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#donluc #sound #programming #arduino #fritzing #electronics #microcontrollers #consultant #vlog

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Brownian Noise

White noise has equal intensity at equal frequencies. This sounds tinny and harsh to humans. The problem is due to the high frequencies. In order to produce a more pleasant sound, we need to attenuate those high frequencies. This is called a “low pass filter”. Brownian noise is noise with a power density which decreases 6 dB per octave with increasing frequency and, when heard, has a “damped” or “soft” quality compared to white and pink noise.

In science is the kind of signal noise produced by Brownian motion, hence its alternative name of random walk noise. The graphic representation of the sound signal mimics a Brownian pattern. The sound is a low roar resembling a waterfall or heavy rainfall.

Brown Noise Sleep Machine

Brown noise can be produced by integrating white noise. That is, whereas white noise can be produced by randomly choosing each sample independently, Brown noise can be produced by adding a random offset to each sample to obtain the next one. Note that while the first sample is random across the entire range that the sound sample can take on, the remaining offsets from there on are a tenth or thereabouts, leaving room for the signal to bounce around.

This is a pretty common diode. It acts as a flyback, a protective measure to against voltage spikes caused by inductive loads, in this case the speaker. It is basically the same setup, except that an electrolytic decoupling capacitors has been added. I found that 33uF to be suitable. If the output sounds too tinny, which I think is unlikely, then increase the capacitance. As you increase the capacitance, the output volume will go down. So you might try experimenting with a lower capacitance and potentiometer.

DL2010Mk01

1 x Arduino Pro Mini 328 – 5V/16MHz
1 x 1K Potentiometer
1 x Knob
1 x Diode Small Signal – 1N4148
1 x Electrolytic Decoupling Capacitors – 33uF/63V
1 x Audio Jack 3.5mm
1 x SparkFun Audio Jack Breakout
1 x Hamburger Mini Speaker
9 x Jumper Wires 3in M/M
1 x Full-Size Breadboard
1 x SparkFun Cerberus USB Cable
1 x SparkFun FTDI Basic Breakout – 5V

Arduino Pro Mini 328 – 5V/16MHz

SPT – Digital 6
VIN – +5V
GND – GND

DL2010Mk01p.ino

// ***** Don Luc Electronics © *****
// Software Version Information
// Project #16: Sound - Brownian Noise - Mk02
// 09-02
// DL2010Mk01p.ino 16-02
// 1 x Arduino Pro Mini 328 - 5V/16MHz
// 1 x 1K Potentiometer
// 1 x Knob
// 1 x Diode Small Signal - 1N4148
// 1 x Electrolytic Decoupling Capacitors - 33uF/63V
// 1 x Audio Jack 3.5mm
// 1 x SparkFun Audio Jack Breakout
// 1 x Hamburger Mini Speaker
// 9 x Jumper Wires 3in M/M
// 1 x Full-Size Breadboard
// 1 x SparkFun Cerberus USB Cable
// 1 x SparkFun FTDI Basic Breakout - 5V

// Include the Library Code

// Mini Speaker
int SPK = 6;
long randNumber;

// Software Version Information
String sver = "16-02";

void loop() {

  // Mini Speaker
  randNumber = random();
  digitalWrite( SPK , randNumber ); 
    
  // Delay the actual frequency of updates
  delayMicroseconds (50);
  
}

setup.ino

// Setup
void setup() {

  // Connect a speaker between ground
  pinMode(SPK, OUTPUT);
  // Random Seed
  randomSeed(analogRead( SPK ));
  
}

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