What this suits
The Pomodoro Technique is a simple work rhythm: 25 minutes of focused work, a short break, repeat — with a longer break after every four rounds. It doesn't require a particular sound, but a lot of people who use it end up wanting one running in the background, mainly to keep the room from going dead silent the second the timer starts, and to mask the noise around them so the timer itself is the only thing demanding attention. Rain is a common default because it stays steady for the full interval instead of looping in a way you notice.
How to pair it
This page starts you with rain at a moderate volume set for focus intervals specifically — during your break, you might prefer it quieter, or off entirely, since the point of a break is to actually step away. If you are doing back-to-back rounds, it is fine to leave rain running continuously through short breaks; save the full stop for your longer break every four rounds.
Suggested session length
The interval this page starts with is the standard 25 minutes on, which is the default Pomodoro length for a reason — long enough to get into real work, short enough to sustain across a full day without burning out. If 25 minutes runs too short or too long for the kind of work you do, the full app lets you adjust focus, short-break, and long-break lengths independently, plus track how many rounds you have completed.