A New Hope

A project log for dBSound Bracelet

This project aims at protecting people's hear when they are under exposure of loud noises such as a live music concert or nightclubs.

dbsound-braceletdBSound Bracelet 03/31/2017 at 08:320 Comments

Hey everyone,

We've made a bunch of things today, let's take a look.

Component List

The component list was updated today (03/24/2017) here are some explanations about what you need to create this project at home. Please note that all the components are still on a test phase and won't all be used. This list will obviously be updated so stay tuned folks !

Micro controller : Adafruit Pro Trinket - 3V 12MHz or Adafruit Trinket - Mini Microcontroller - 3.3V Logic

Both were chosen because of their size, they'll make easier the final integration on the bracelet. However they are still very powerful and can be almost coded like a classic arduino. The main difference between the Pro Trinket and the Trinket Mini is the size, and so the CPU attached on those. Maybe the mini specs (ATtiny85, 8K of flash, 512 byte of SRAM, 512 bytes of EEPROM) will be a bit low, but we will see in a few weeks !

Electret Microphones : Adafruit MAX4466 or MAX9814 or SPW2430

Several ones were chosen, because we are afraid of saturation and resolution. We don't want the mic to be saturated at 100dB for example. It would be a shame because we want to detect the sound up to 130dB at least. The MAX4466 is quite classical and has an integrated op-AMP and gain can change from 25x to 125x while the MAX9814 has an automatic gain control. However "max gain" can obviously me modified. Finally the SPW2430 is the smaller one and probably the best for audio detection while the two previous ones can be used for recording/sampling - but "the output peak-to-peak voltage has a 0.67V DC bias and about 100mVpp" - so it's the more likly to clip/sature on high-level sounds. So at this point we don't have any favorites !


First of all we wanted super tiny and basic leds but then we moved to adafruit's Neopixels. They are way much bigger than what we looked at the beginning but they are also way much cooler because you can change color and use a Bus to control them, it means less wiring and we love that !


Feel free to take a look at our schedule, so you won't miss any updates. They'll be mostly posted every wednesday, when we are at the CRI Paris, France.


Bertrand started working on the code, he'll use or at least fin inspiration on the following one wich was created by adafruit (them, again). It's quite close from what we're trying to do, but in a different way and with different objectives (however this is a rad tie).

Adafruit related project :

Here is the raw code (our's will be a lot easier)

LED VU meter for Arduino and Adafruit NeoPixel LEDs.
 Hardware requirements:
 - Most Arduino or Arduino-compatible boards (ATmega 328P or better).
 - Adafruit Electret Microphone Amplifier (ID: 1063)
 - Adafruit Flora RGB Smart Pixels (ID: 1260)
 - Adafruit NeoPixel Digital LED strip (ID: 1138)
 - Optional: battery for portable use (else power through USB or adapter)
 Software requirements:
 - Adafruit NeoPixel library
 - 3.3V to mic amp +
 - GND to mic amp -
 - Analog pin to microphone output (configurable below)
 - Digital pin to LED data input (configurable below)
 See notes in setup() regarding 5V vs. 3.3V boards - there may be an
 extra connection to make and one line of code to enable or disable.
 Written by Adafruit Industries.  Distributed under the BSD license.
 This paragraph must be included in any redistribution.
 fscale function:
 Floating Point Autoscale Function V0.1
 Written by Paul Badger 2007
 Modified from code by Greg Shakar

#include <Adafruit_NeoPixel.h>
#include <math.h>

#define N_PIXELS  16  // Number of pixels in strand
#define MIC_PIN   A9  // Microphone is attached to this analog pin
#define LED_PIN    6  // NeoPixel LED strand is connected to this pin
#define SAMPLE_WINDOW   10  // Sample window for average level
#define PEAK_HANG 24 //Time of pause before peak dot falls
#define PEAK_FALL 4 //Rate of falling peak dot
#define INPUT_FLOOR 10 //Lower range of analogRead input
#define INPUT_CEILING 300 //Max range of analogRead input, the lower the value the more sensitive (1023 = max)

byte peak = 16;      // Peak level of column; used for falling dots
unsigned int sample;

byte dotCount = 0;  //Frame counter for peak dot
byte dotHangCount = 0; //Frame counter for holding peak dot

Adafruit_NeoPixel strip = Adafruit_NeoPixel(N_PIXELS, LED_PIN, NEO_GRB + NEO_KHZ800);

void setup() 
  // This is only needed on 5V Arduinos (Uno, Leonardo, etc.).
  // Connect 3.3V to mic AND TO AREF ON ARDUINO and enable this
  // line.  Audio samples are 'cleaner' at 3.3V.
  //  analogReference(EXTERNAL);

  // Serial.begin(9600);
  strip.begin();; // Initialize all pixels to 'off'


void loop() 
  unsigned long startMillis= millis();  // Start of sample window
  float peakToPeak = 0;   // peak-to-peak level

  unsigned int signalMax = 0;
  unsigned int signalMin = 1023;
  unsigned int c, y;

  // collect data for length of sample window (in mS)
  while (millis() - startMillis < SAMPLE_WINDOW)
    sample = analogRead(MIC_PIN);
    if (sample < 1024)  // toss out spurious readings
      if (sample > signalMax)
        signalMax = sample;  // save just the max levels
      else if (sample < signalMin)
        signalMin = sample;  // save just the min levels
  peakToPeak = signalMax - signalMin;  // max - min = peak-peak amplitude
  // Serial.println(peakToPeak);

  //Fill the strip with rainbow gradient
  for (int i=0;i<=strip.numPixels()-1;i++){

  //Scale the input logarithmically instead of linearly
  c = fscale(INPUT_FLOOR, INPUT_CEILING, strip.numPixels(), 0, peakToPeak, 2);


  if(c < peak) {
    peak = c;        // Keep dot on top
    dotHangCount = 0;    // make the dot hang before falling
  if (c <= strip.numPixels()) { // Fill partial column with off pixels
    drawLine(strip.numPixels(), strip.numPixels()-c, strip.Color(0, 0, 0));

  // Set the peak dot to match the rainbow gradient
  y = strip.numPixels() - peak;

  // Frame based peak dot animation
  if(dotHangCount > PEAK_HANG) { //Peak pause length
    if(++dotCount >= PEAK_FALL) { //Fall rate 
      dotCount = 0;
  else {

//Used to draw a line between two points of a given color
void drawLine(uint8_t from, uint8_t to, uint32_t c) {
  uint8_t fromTemp;
  if (from > to) {
    fromTemp = from;
    from = to;
    to = fromTemp;
  for(int i=from; i<=to; i++){
    strip.setPixelColor(i, c);

float fscale( float originalMin, float originalMax, float newBegin, float
newEnd, float inputValue, float curve){

  float OriginalRange = 0;
  float NewRange = 0;
  float zeroRefCurVal = 0;
  float normalizedCurVal = 0;
  float rangedValue = 0;
  boolean invFlag = 0;

  // condition curve parameter
  // limit range

  if (curve > 10) curve = 10;
  if (curve < -10) curve = -10;

  curve = (curve * -.1) ; // - invert and scale - this seems more intuitive - postive numbers give more weight to high end on output 
  curve = pow(10, curve); // convert linear scale into lograthimic exponent for other pow function

   Serial.println(curve * 100, DEC);   // multply by 100 to preserve resolution  

  // Check for out of range inputValues
  if (inputValue < originalMin) {
    inputValue = originalMin;
  if (inputValue > originalMax) {
    inputValue = originalMax;

  // Zero Refference the values
  OriginalRange = originalMax - originalMin;

  if (newEnd > newBegin){ 
    NewRange = newEnd - newBegin;
    NewRange = newBegin - newEnd; 
    invFlag = 1;

  zeroRefCurVal = inputValue - originalMin;
  normalizedCurVal  =  zeroRefCurVal / OriginalRange;   // normalize to 0 - 1 float

  // Check for originalMin > originalMax  - the math for all other cases i.e. negative numbers seems to work out fine 
  if (originalMin > originalMax ) {
    return 0;

  if (invFlag == 0){
    rangedValue =  (pow(normalizedCurVal, curve) * NewRange) + newBegin;

  else     // invert the ranges
    rangedValue =  newBegin - (pow(normalizedCurVal, curve) * NewRange); 

  return rangedValue;

// Input a value 0 to 255 to get a color value.
// The colours are a transition r - g - b - back to r.
uint32_t Wheel(byte WheelPos) {
  if(WheelPos < 85) {
    return strip.Color(WheelPos * 3, 255 - WheelPos * 3, 0);
  else if(WheelPos < 170) {
    WheelPos -= 85;
    return strip.Color(255 - WheelPos * 3, 0, WheelPos * 3);
  else {
    WheelPos -= 170;
    return strip.Color(0, WheelPos * 3, 255 - WheelPos * 3);
}--------- more ----------