Instead of using a keypad to open your front door or even your safe, why not control the mechanism by a slider that glides through pitches?

Simple, easy to build 2 x 14 bars stereo VU meter for representing audio level.

Wanna try to become the new super stylish 2020s drummer?

This tutorial shows how to detect noise level though the mic in your smartphone.

This project produces an audible warning with LED buzzer ISD1820 output when KY-037 input signal is over the limit.