This page is using unicode characters' code to play sound. By default, it plays back the copyright sign's code, 169 (Hz) with the Registered TM sign's code (174). One thread creates new elements, the other colorizes them, the third looks for colorized ones, and when founds, remove the color and triggers the sound. You can change ® to Your own by pressing a key, or simply deleting everything by moving the mouse:)
Created by Balázs Kovács, during a DAAD scholarship at ICEM-Folkwang Hochschule, Essen, 2016. Pluck sound is created with the help of the Timbre.JS library.