If you have generated a pure tone in code and played it back, you may have noticed a small click at the start, the end, or both. The tone itself is clean, but the edges are not. That click is not a bug in your sine wave.
Source: [Dev.to](https://dev.to/mwiginton/why-your-generated-tone-clicks-and-how-an-envelope-fixes-it-1p89)