Why Synthesized Tones Click and How an Envelope Smooths Them Out

When generating audio tones in code, a common artifact is an audible click at the start or end of playback, caused by abrupt jumps in sample values rather than any flaw in the sine wave itself. This happens because a speaker cone at rest must instantly shift to a non-zero sample position, creating a sharp air movement the ear perceives as a pop. The fix is an envelope — a gain value between 0.0 and 1.0 multiplied against each sample — that gradually ramps volume up at the start and back down at the end. The rising portion, called the attack, and the falling portion, called the release, ensure the signal begins and ends near zero, eliminating the abrupt transitions. Implemented in plain C++ without external libraries, a 10-millisecond attack and 50-millisecond release are sufficient to remove the click entirely.