It's because there's no load
It's because there's no load on the engine. When it's in drive, there is a load. Hence higher compression is needed to make the engine turn and cause the car to go. Higher compression = more noise.
It's because there's no load on the engine. When it's in drive, there is a load. Hence higher compression is needed to make the engine turn and cause the car to go. Higher compression = more noise.