Why has another iPhone 8 Plus speaker failed?

I had a new iPhone 8Plus that lasted about 1 year before its speaker started to get so low I couldn’t hear anything. I took it in and after the tests Apple agreed to replace it. Then a few months later the next 8Plus I got did the same thing. Speaker volume gets quieter and quieter until you notice its broken again. I have several friends with 8’s and 8 Plus and they also report this issue. Does anyone else with an 8 or 8 Plus have this problem while using speakerphone? Put it next to a 7 or 11 and it sounds like its muted in comparison.