IOS 17.0.3 phone ringing when silenced

I just updated my iPhone 14 pro from IOS 16 something to IOS 17 (I'd missed a few updates) so I don't know if this is a new thing or if it's an IOS 17 thing.

I always have my phone on silent. ALWAYS. But now when someone's calling me my phone is vibrating but also emitting a noise I've never heard before? It doesn't resemble my usual ring tone at all and I can't find any information about this anywhere. How do I remove this? It's so unbelievably annoying. Like if I'm sat in class and someone calls me and even though I have my phone on silent, IT STILL MAKES NOISE??

I even have an Apple Watch series 8 and even though both devices are on silent the noise still comes through on my phone. My Apple Watch vibrates as usual, it's just my phone that's acting weird.

Please help.