Electret Microphone Amplifier

Electret Microphone Amplifier

Simple Arduino example to print out noise level values using a microphone (Adafruit MAX4466).

Components

1 x electret microphone (Adafruit MAX4466)
1 x Arduino Uno
1 x breadboard
jumper wires
 

Setup

Arduino sketch

Inspect Serial monitor (9600) for sensor values (converted to volts).

/*
 MAX4466 (adafruit mic)
 
 Written by Shani Mensing, edited by Audrey St. John
 
 Circuit: microphone VCC connected to 3.3V, OUT to analog input A0
 */

// hook up the out of the mic to analog input A0
#define MIC_IN A0

// Sample window width in milliseconds (50 ms = 20Hz)
int sampleWindow = 50; 

/**
 * Initialization code
 **/
void setup()
{
   // open serial port and set data rates to 9600 bps (bits-per-second)
   // this lets us communicate to/from the arduino
   Serial.begin(9600);
   
   pinMode( MIC_IN, INPUT );
}

/**
 * Main program loop happens constantly.
 **/
void loop()
{
    // read the analog sensor as volts
    double soundSensed = sampleSoundPeak();
    
    // convert to volts
    double volts = (soundSensed * 3.3) / 1024; 
    
    // print it out
    Serial.println(volts);
}

/////////////// Our own methods

/**
 * Sense biggest input difference are being input from the analog MIC sensor
 * over a certain "window" of time. 
 * Values returned are in the range 0 - 1024.
 **/
double sampleSoundPeak()
{
    // record start time 
    double startMillis = millis(); 

    // this will be the highest peak, so start it very small    
    int signalMax = 0;
    
    // this will be the lowest peak, so start it very high
    int signalMin = 1024;
    
    // will hold the current value from the microphone
    int sample;
    
    // collect data for 50 ms
    while ( (millis() - startMillis) < sampleWindow ) 
    {
        // read a value from mic and record it into sample variable
        sample = analogRead( MIC_IN );
        
        // toss out spurious readings
        if (sample < 1024)
        {
        
            // if the current sample is larger than the max
             if (sample > signalMax)
             {      
                   // this is the new max -- save it
                   signalMax = sample; 
             }
             // otherwise, if the current sample is smaller than the min
             else if (sample < signalMin)
             {
                   // this is the new min -- save it
                   signalMin = sample; 
             }
         }
     }
     
     // now that we've collected our data,
     // determine the peak-peak amplitude as max - min
     int peakDifference = signalMax - signalMin; 
    
     // give it back to the caller of this method
     return peakDifference;
}