Text message notifications are making an EXTREMELY loud sound.

So, I recently switched over from iPhone Xs to iPhone 11. The software version is 14.2. Before I switched to the iPhone 11, I have never had this problem on my iPhone Xs or even my iPod 6th Generation, iPad Air 2, or even iPad 2, or MacBook. None of them have had this problem. The problem is when I get a text message, *SOMETIMES* it will start off at normal volume for a split second, and then the notification sound will start playing at EXTREMELY loud volume, and I, who has very sensitive ears and doesn't expect it, usually jump up in surprise. I can try to get footage of this glitch, but so far, I have none. If I manage to get footage of the notification playing, I will update this. Please help. This is very annoying.