@ScottScott that's the problem with these swim plugs. The do reduce sound by about 25dB. That's the trade off for solid water protection. When I really want to make sure I'm watertight, I will even add a thin layer of vaseline to my custom plugs. This makes them even more sound cancelling.
Biggest issue for me is when I'm taking a lesson and the instructor is giving me pointers. I can still hear Jodi's whistles at me when I'm skiing, but it can be hard just hearing a normal voice in between runs.