Sound Detector Hookup Guide

Contributors: Byron J.
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Software Example

Now that we understand how to configure the board, let's hook it to an Arduino and see what it can do.


In addition to the Sound Detector, you'll need the following parts.


We snapped a 5-pin section off the header, and soldered it to the Sound Detector. Then we took the jumper wires and made the following connections.

(Sound Detector → Arduino )

  • GND → Supply Ground
  • VCC → Power supply voltage between 3.5 and 5.5 Volts
  • Gate → Pin 2
  • Envelope → A0

Additionally, as described on the calibration page, a 33K Ohm resistor was soldered into position R17. R3 was left in place, so the gain was lowered from 40 dB to about 28 dB.

 * sound_detector_demo.ino
 * Sound detector sample sketch
 * Byron Jacquot @ SparkFun Electronics
 * February 19, 2014
 * This sketch demonstrates the use of the Sparkfun Sound Detector board.
 * The Sound Detector is a small board that combines a microphone and some 
 * processing circuitry.  It provides not only an audio output, but also a 
 * binary indication of the presence of sound and an analog representation 
 * of it's amplitude.  
 * This sketch demonstrates two different modes of usage for the Sound
 * Detector.  The gate output (a binary indication that is high when sound
 * is present, and low when conditions are quiet) is used to fire a pin-change 
 * ISR, which lights an LED when the sound is present.  The envelope output 
 * (an analog voltage to rises to indicate the amplitude of the sound) is 
 * sampled in the loop(), and it prints an indication of the level to the 
 * serial terminal. 
 * For more details about the Sound Detector, please check the hookup guide.
 * Connections:
 * The Sound Detector is connected to the Adrduino as follows:
 * (Sound Detector -> Arduino pin)
 * GND → GND
 * VCC → 5V
 * Gate → Pin 2
 * Envelope → A0
 * Resources:
 * Additional library requirements: none
 * Development environment specifics:
 * Using Arduino IDe 1.0.5
 * Tested on Redboard, 3.3v/8MHz and 5v/16MHz ProMini hardware.
 * This code is beerware; if you see me (or any other SparkFun employee) at the
 * local, and you've found our code helpful, please buy us a round!
 * Distributed as-is; no warranty is given.

 // Define hardware connections
#define PIN_GATE_IN 2
#define IRQ_GATE_IN  0
#define PIN_LED_OUT 13
#define PIN_ANALOG_IN A0

// soundISR()
// This function is installed as an interrupt service routine for the pin
// change interrupt.  When digital input 2 changes state, this routine
// is called.
// It queries the state of that pin, and sets the onboard LED to reflect that 
// pin's state.
void soundISR()
  int pin_val;

  pin_val = digitalRead(PIN_GATE_IN);
  digitalWrite(PIN_LED_OUT, pin_val);   

void setup()

  //  Configure LED pin as output

  // configure input to interrupt
  pinMode(PIN_GATE_IN, INPUT);
  attachInterrupt(IRQ_GATE_IN, soundISR, CHANGE);

  // Display status

void loop()
  int value;

  // Check the envelope input
  value = analogRead(PIN_ANALOG_IN);

  // Convert envelope value into a message
  Serial.print("Status: ");
  if(value <= 10)
  else if( (value > 10) && ( value <= 30) )
  else if(value > 30)

  // pause for 1 second

This code simultaneously demonstrates two different operating modes of the Sound Detector.

  • First, using the external interrupt facility, the Arduino observes the gate output, and sets the onboard (pin 13) LED to follow the gate status.
  • Second, in the loop() routine, it uses an analog input to periodically sample the envelope signal. That value is interpreted into a message indicating the current loudness via a series of thresholds.