you're dumb, they are not the same thing, AT ALL.
edit: to elaborate, the wastegate bleeds EXHAUST gasses off to keep the turbo from over boosting, the blow off valve(or pop off valve or like 10^10 other names) bleeds air from the INTAKE side to alleviate compressor surge.
two different devices, two different purposes. No, they are not basically the same thing, at all.
also, both BOVs and wastegates can be loud or silent, depending on thier design and how you run them. The twin Tial setup on a friends old saab could DEFINATELY be heard when it opened up, but my stock WG barely makes a peep. My stock BOV makes no discernable noise, but my SSQV is quite loud.