This breaker operates pool equipment outside. It buzzes when under load, so I think I should replace it. Can’t find it online, Any suggestions on what to use in it’s place? YF-6738 Eidt: my box is not T&B like in this question: Compatibility for Thomas & Betts breakers
The buzzing is a sign of an alien (breaker) invasion!
Your panel is a Murray panel from the Siemens era, which means that it uses Siemens breakers as the corresponding Murray part numbers (same breaker, different paper label) were discontinued a few years ago by Siemens in order to regularize their product line. As a result, I'd check the multi-wire branch circuit situation out first to avoid a slow-cooked neutral; worse comes to worse, you can nut the black and red wires from that circuit to a 12AWG pigtail to a single breaker, provided the circuit's loading permits that of course.
Once that's resolved, we can take care of the buzzing. The existing breakers are Eaton BR (BD) and T&B (similar to Eaton), and the T&B in particular isn't quite fitting right into the Murray panel you have, hence the noises, which are a sign of arcing and potential damage. If the busbar stabs are still good when you pull things out, you can replace the alien breakers with a Q120 and a Q2020, deporting them from your panel for good.