SENSORS/ACTUATORS

INTERNET OF THING (IoT)

ESP32 UNO - Sound Sensor

Need your ESP32 Uno to notice a clap or a loud bang? Connect a sound sensor to the ESP32 Uno form board and watch the Serial Monitor print a line each time a sound starts and stops. A sound detector module is cheap, and it needs only one signal wire.

By the end, you can:

Wire a sound sensor to the ESP32 Uno at 3.3V
Read the sensor output with digitalRead()
Print a message when a sound starts and when it ends
Tune the sensitivity with the on-board potentiometer

When this works, you can extend the sketch to switch on an LED, a lamp through a relay, or a servo motor each time the module hears a sound.

Components You Need

1	×	ESP32 Uno-form Board
1	×	USB Cable Type-A to Type-C (for USB-A PC)
1	×	USB Cable Type-C to Type-C (for USB-C PC)
1	×	Digital Sound Sensor
1	×	Analog Sound Sensor
1	×	Jumper Wires

Or you can buy the following kits:

DIYables Sensor Kit (18 sensors/displays)

Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables .

Overview of the Sound Sensor

By the end of this part, you know which module you hold and what each pin does.

Module	Pins	Output
Digital sound sensor	VCC, GND, OUT	HIGH or LOW only
Analog sound sensor	+, G, DO, AO	HIGH or LOW on DO, changing voltage on AO

Both modules carry a tiny trimmer that decides how loud a sound has to be to flip the digital pin.

Digital Sound Sensor Pinout

Pin	Role
VCC	Power, 3.3V to 5V (use 3.3V with the ESP32 Uno)
GND	Ground (0V)
OUT	Signal. HIGH when quiet, LOW when a sound is heard

image source: diyables.io

The module also has two small LEDs. One shows power. The other lights up while the microphone hears a sound.

Analog Sound Sensor Pinout

Pin	Role
+	Power. Feed it 3.3V from the ESP32 Uno
G	Ground (0V)
DO	Digital output. HIGH when quiet, LOW when a sound is heard
AO	Analog output. The voltage follows the sound level

image source: diyables.io

This module has the same potentiometer and the same two LEDs. The sketch on this page only uses the digital pin, so wire OUT (or DO) and ignore AO.

How It Works

The potentiometer sets a loudness threshold.

Sound louder than the threshold: the output goes LOW.
Sound quieter than the threshold: the output stays HIGH.

Good to know: The signal is flipped. A LOW reading in your sketch is a sound, and HIGH is silence.

ESP32 Uno Pinout

Match each Uno header label to its GPIO number in the picture before you place any wire. Your sketch uses the GPIO number, not the label.

How to Connect

Goal: the sensor gets power from 3.3V and sends its signal to D7.

The wiring diagram between ESP32 Uno Sound Sensor

This image is created using Fritzing. Click to enlarge image

Module Pin	ESP32 Uno Pin
VCC	3.3V
GND	GND
OUT	D7 (GPIO14)

※ NOTE THAT:

The wiring diagram may not show the correct pin. On the ESP32 Uno, the sensor OUT goes to D7 (GPIO14), not D8 as the picture may show. We will update the diagram soon. Until then, follow the wiring table and the code on this page, not the picture.

Good to know: ESP32 Uno pins work at 3.3V and are not 5V tolerant. A sensor powered from 5V also outputs 5V on OUT, so keep it on 3.3V.

Programming the Sound Sensor

By the end of this part, you know the two functions the sketch needs.

Step 1 — Set the pin as an input

Use pinMode() once in setup(). Here the pin is GPIO14, the D7 header.

pinMode(14, INPUT);

Step 2 — Read the pin

Call digitalRead() again and again in loop(). A LOW result means a sound.

int soundState = digitalRead(14);

Code

The sketch watches the sensor pin and prints a line only when its level changes, so one sound gives one "detected" line and one "disappeared" line.

Code Part	What It Does
SENSOR_PIN 14	Names the pin wired to OUT (D7, GPIO14)
prev_sound_state	Stores the level from the last pass
digitalRead(SENSOR_PIN)	Reads the new level, LOW means sound
HIGH to LOW change	Prints "The sound has been detected"
LOW to HIGH change	Prints "The sound has disappeared"

Result: you get two clean messages per sound instead of a flood of lines.

Upload and Test

First time with this board? Set it up with ESP32 Uno - Getting Started before you continue.
Build the circuit by following the wiring table above.
Plug in the USB Type-C cable between the ESP32 Uno and your computer.
Select the board in Arduino IDE: pick ESP32 Dev Module and the COM port of the board (CH340).
Copy the code above into a new sketch.
Click the Upload button to send it to the board.
Open the Serial Monitor, then pick 9600 baud in the drop-down.
Clap once near the sensor and check the output.

Newbiely | Arduino IDE 2.3.8

──

☐

Newbiely.ino

···

8 Serial.println("Hello World!");

Output

Serial Monitor

Message (Enter to send message to 'ESP32 Dev Module' on 'COM15')

New Line

9600 baud

The sound has been detected The sound has disappeared The sound has been detected The sound has disappeared The sound has been detected

Ln 11, Col 1

ESP32 Dev Module on COM15

Pro tip: Hold the module in your hand and snap your fingers at about 5 cm. If the sound LED stays on in a quiet room, turn the potentiometer a little with a small screwdriver until it goes off.

Video Tutorial

See the ESP32 Uno build in action in the video below.

The demo counts your claps and starts a light show on a row of 8 LEDs: 1 clap = all blink, 2 claps = water wave, 3 claps = center to edges, 4 claps = random dance. These LEDs light up when their pin is pulled LOW (active-LOW wiring).

Part	ESP32 Uno Pin
Sensor OUT	D10 (GPIO5)
LEDs 1-4	D2 (GPIO26), D3 (GPIO25), D4 (GPIO17), D5 (GPIO16)
LEDs 5-8	D6 (GPIO27), D7 (GPIO14), D8 (GPIO12), D9 (GPIO13)

This demo uses D10 (GPIO5) for the sensor OUT. The chip reads this pin at power-up. If the board does not boot or fails to upload, unplug the wire from D10, upload the code, then plug it back in. The LED on D8 goes to GND through a resistor, so it is safe.

/* * This ESP32 Uno code was developed by newbiely.com * * This ESP32 Uno code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp32-uno/esp32-uno-sound-sensor */ //===================================================== // CLAP COUNTER WITH LED LIGHT SHOWS // 1 clap -> all LEDs blink // 2 claps -> water wave // 3 claps -> inside out // 4 claps -> random dance //===================================================== #define SOUND_PIN 5 // D10 (GPIO5) reads the sound sensor OUT pin // D2, D3, D4, D5, D6, D7, D8, D9 -> GPIO26, 25, 17, 16, 27, 14, 12, 13 const byte LED_PINS[] = {26,25,17,16,27,14,12,13}; const byte NUM_LEDS = sizeof(LED_PINS); const unsigned long CLAP_DEBOUNCE = 80; // ignore claps closer than this (ms) const unsigned long CLAP_TIMEOUT = 700; // wait this long for the next clap (ms) //----------------------------------------------------- // Clap tracking //----------------------------------------------------- bool lastSound = HIGH; unsigned long lastClapTime = 0; byte clapCount = 0; bool waitingSequence = false; //----------------------------------------------------- // Which light show is running //----------------------------------------------------- byte currentEffect = 0; //----------------------------------------------------- // Show 1 state //----------------------------------------------------- unsigned long blinkTimer = 0; bool blinkState = false; //----------------------------------------------------- // Show 2 state //----------------------------------------------------- unsigned long waveTimer = 0; int waveIndex = 0; //----------------------------------------------------- // Show 3 state //----------------------------------------------------- unsigned long insideTimer = 0; int insideStep = 0; //----------------------------------------------------- // Show 4 state //----------------------------------------------------- unsigned long danceTimer = 0; //===================================================== void setup() { Serial.begin(115200); pinMode(SOUND_PIN, INPUT); for(int i=0;i<NUM_LEDS;i++) { pinMode(LED_PINS[i], OUTPUT); digitalWrite(LED_PINS[i], HIGH); // HIGH = LED off (active-LOW) } randomSeed(analogRead(2)); // A0 (GPIO2) floating pin gives random noise Serial.println("System Ready"); } //===================================================== void loop() { detectClaps(); runEffect(); } //===================================================== // CLAP COUNTING //===================================================== void detectClaps() { bool soundValue = digitalRead(SOUND_PIN); unsigned long now = millis(); // a HIGH to LOW change means a new clap if(lastSound == HIGH && soundValue == LOW) { if(now - lastClapTime > CLAP_DEBOUNCE) { clapCount++; lastClapTime = now; waitingSequence = true; Serial.print("Clap: "); Serial.println(clapCount); } } lastSound = soundValue; // no new clap for a while, so the count is final if(waitingSequence && (now - lastClapTime > CLAP_TIMEOUT)) { if(clapCount >= 1 && clapCount <= 4) { currentEffect = clapCount; Serial.print("Effect = "); Serial.println(currentEffect); resetEffectState(); } clapCount = 0; waitingSequence = false; } } //===================================================== void resetEffectState() { turnOffAll(); blinkState = false; waveIndex = 0; insideStep = 0; blinkTimer = waveTimer = insideTimer = danceTimer = millis(); } //===================================================== void turnOffAll() { for(int i=0;i<NUM_LEDS;i++) { digitalWrite(LED_PINS[i], HIGH); } } //===================================================== void runEffect() { switch(currentEffect) { case 1: effectBlinkAll(); break; case 2: effectWaterWave(); break; case 3: effectInsideOut(); break; case 4: effectDance(); break; default: break; } } //===================================================== // SHOW 1: BLINK ALL //===================================================== void effectBlinkAll() { if(millis() - blinkTimer >= 200) { blinkTimer = millis(); blinkState = !blinkState; for(int i=0;i<NUM_LEDS;i++) { digitalWrite( LED_PINS[i], blinkState ? LOW : HIGH ); } } } //===================================================== // SHOW 2: WATER WAVE //===================================================== void effectWaterWave() { if(millis() - waveTimer >= 70) { waveTimer = millis(); turnOffAll(); digitalWrite( LED_PINS[waveIndex], LOW ); waveIndex++; if(waveIndex >= NUM_LEDS) { waveIndex = 0; } } } //===================================================== // SHOW 3: INSIDE OUT //===================================================== void effectInsideOut() { if(millis() - insideTimer >= 120) { insideTimer = millis(); turnOffAll(); switch(insideStep) { case 0: digitalWrite(LED_PINS[3], LOW); digitalWrite(LED_PINS[4], LOW); break; case 1: digitalWrite(LED_PINS[2], LOW); digitalWrite(LED_PINS[5], LOW); break; case 2: digitalWrite(LED_PINS[1], LOW); digitalWrite(LED_PINS[6], LOW); break; case 3: digitalWrite(LED_PINS[0], LOW); digitalWrite(LED_PINS[7], LOW); break; } insideStep++; if(insideStep > 3) { insideStep = 0; } } } //===================================================== // SHOW 4: RANDOM DANCE //===================================================== void effectDance() { if(millis() - danceTimer >= 80) { danceTimer = millis(); turnOffAll(); int a = random(NUM_LEDS); int b = random(NUM_LEDS); int c = random(NUM_LEDS); digitalWrite(LED_PINS[a], LOW); digitalWrite(LED_PINS[b], LOW); digitalWrite(LED_PINS[c], LOW); } }

ESP32 Uno vs UNO R4 for This Project

Moving this project from the UNO R4 to the ESP32 Uno changes the pin numbers and the voltage.

Item	Arduino UNO R4	ESP32 Uno
Logic voltage	5V	3.3V
Sensor OUT pin in code	8	14 (D7)
Sensor power	5V or 3.3V	3.3V
Demo sensor pin	10	5 (D10)
Arduino IDE board	Arduino UNO R4 WiFi	ESP32 Dev Module
Wireless	WiFi on the WiFi model	WiFi and Bluetooth built in

The wiring stays on the same Uno header positions, so you can reuse the layout. Only the numbers in the code change, and the sensor must run from 3.3V.

Tips for Steadier Detection

A sound sensor is a small analog circuit, so its surroundings matter.

Tip	Why It Helps
Turn the potentiometer in small steps	Tiny turns change the threshold a lot
Fix the module on a solid surface	Table bumps and wind are not counted as sounds
Test within about 10 inches (25 cm)	The microphone hears only nearby sounds
Use short wires and a stable supply	Power noise can trigger false alarms

Go Wireless: Sound Alerts on Your Phone

Goal: see the sound events on your phone instead of a cable and a computer.

The ESP32 Uno has WiFi and Bluetooth, so the sensor can report to a browser or the DIYables Bluetooth app. Send "sound detected" lines to a wireless monitor, or plot the sound level over time.

Try These Next

Turn on an LED while the sound LED is lit.
Toggle a relay on every clap.
Count claps and run a different action for each count.

Function References

Troubleshooting

Problem	Possible Cause	Solution
No COM port in Arduino IDE	CH340 driver missing or charge-only cable	Install the CH340 driver and use a data USB cable
Upload fails with "Failed to connect" or "Waiting for download"	Board not in download mode	Hold the BOOT button while the upload starts
Serial Monitor shows garbage or stays empty	Baud rate does not match Serial.begin(9600)	Choose 9600 in the monitor
Nothing prints when you clap	Sensitivity too low or OUT on the wrong pin	Turn the potentiometer and check OUT goes to D7 (GPIO14)
Messages print in a silent room	Sensitivity too high or power noise	Turn the potentiometer back and use short wires
Power LED on the module is off	VCC or GND wire loose	Check the 3.3V and GND wires
Pin stops responding after a while	Sensor on 5V sends 5V into a 3.3V pin	Power the sensor from 3.3V
Random triggers when the motor or relay switches	Power noise on the supply	Power the sensor from a stable source and keep wires short

FAQ

How does a digital sound sensor detect a clap?

A microphone on the module feeds a comparator. When the sound is louder than the level set by the potentiometer, the comparator pulls OUT LOW. The ESP32 Uno sees that change and prints a message.

Can I power the sound sensor from 5V with the ESP32 Uno?

The module runs at 5V, but then OUT also swings to 5V. ESP32 Uno pins are not 5V tolerant, so use the 3.3V pin or add a voltage divider on OUT.

Why does the code print "detected" when the pin goes LOW?

The module pulls its pin down when it hears something. In silence the pin rests at HIGH, so the sketch looks for the HIGH to LOW edge.

Can the sensor tell the difference between voices and claps?

No. It only reports that a sound passed the loudness threshold. Speech recognition needs a different module or library.

Can I use the AO pin of the analog sound sensor on the ESP32 Uno?

Yes. Connect AO to an analog header pin and read it with analogRead(). The ESP32 Uno ADC is 12-bit, so values run from 0 to 4095. Add analogSetAttenuation(ADC_11db); in setup() to read the full range up to about 3.3V.

Which pin can I use for the sensor besides D7?

Any normal digital pin works, for example D6 (GPIO27) or D9 (GPIO13). Avoid D0 and D1 because they carry the USB serial. Avoid boot strapping pins such as D8 (GPIO12) and D10 (GPIO5) when you can.

Can I use A2 to A5 for the sound sensor OUT pin?

Yes, as an input. A2 to A5 (GPIO35, 34, 36, 39) are input only and have no internal pull-up, which is fine for a sensor that drives the line itself.

Does analogRead() on A0 or A1 work when WiFi is on?

No. A0 (GPIO2) and A1 (GPIO4) are ADC2 pins, and ADC2 cannot be read while WiFi is on. For analog sound reading in a WiFi project, use A2 to A5 or GPIO32 and GPIO33.

Will the CH340 driver matter for this project?

Yes. The ESP32 Uno uses a CH340 USB chip. If no COM port appears, install the CH340 driver and try a data cable.

Can I show the sound events on a web page?

Yes. The ESP32 Uno has WiFi and Bluetooth. Use the web monitor or the Bluetooth app monitor from the Go Wireless section.

What if I run out of header pins for my project?

The ESP32 Uno has a few extra holes near the power header. GPIO32 and GPIO33 support I/O, PWM and analog on ADC1, so they also work while WiFi is on. GPIO15 supports I/O, PWM and analog on ADC2. Solder headers first, then use the GPIO number directly in your sketch. For a second sound sensor, use GPIO32 or GPIO33 first. Two warnings apply. First, GPIO15 and GPIO0 (the IO0 pin at the unused Uno NC position) are boot strapping pins, and a wrong connection can stop the board from booting or uploading code, so use GPIO32 and GPIO33 first. Second, never use the six holes under the digital header (SD0 to SD3, CMD, CLK = GPIO6 to GPIO11). They are wired to the flash chip, and using them crashes the board.

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