Aside from the Uno and the ultrasonic sensor, you also need a PHPoC Shield to connect the board to the internet and a power supply to power up your Arduino.

What this project does is produce seven different tones (middle C, D, E, F, G, A, and B) with only an Arduino UNO, ultrasonic sensor, force-sensitive resistor (or push button), and piezo buzzer.

This is an Arduino-based Proximity Sensor circuit wired using the popular HC-SR04 Ultrasonic ranging module,used here for non-contact object detection purpose. The HC-SR04 module includes ultrasonic ...