a video comparing the new M5's noise when equipped with its standard exhaust and with its optional M Sport exhaust. The M Sport system uses flaps in the exhaust that open and close depending on drive mode, increasing or decreasing volume.
You can still hear the vaguely flat-plane V8 noise of the old M5 here, though. BMW's 4.4-liter V8 doesn't actually have a flat-plane crankshaft, but as we explained back in 2014, it does have a crossover exhaust manifold that sends an evenly-spaced pulse of air to each exhaust pipe. That's why both the previous- and current-gen M5's V8 has a McLaren-esque sound, even though it uses a cross-plane crankshaft.
So, the new M5 doesn't have quite the same thunderous sound of a Mercedes-AMG, but it's a lot better than the old one. It even sounds nice without the standard exhaust.