Smaller engines - specifically those under the 2.0 liter size- typically have more NVH (noise, vibration, harshness) at high RPM than larger displacement engines. The larger 4 cylinders (2.3 and bigger typically) have a fairly hefty counterweight on the crankshaft to smooth out the vibration from much more evident power strokes. Engines become even noisier still when you're forcing more air into the cylinders than they can suck in on their own.
4 cylinder engines also have a power stroke only every 180 degrees instead of the 120 or less of an engine with more cylinders. Because there is a full stroke in the 720* rotation without a power stroke, a 4 cylinder will always sound more "buzzy" than a 6 or 8 cylinder engine, no matter what engineering team designed it.
We've got a pair of large displacement (2.4/2.5) Honda/Toyota 4 cylinder engines in the family. Compared to the Cruze, I'd say they're noisier at startup and lower RPMs and butter smooth at above 3000 RPMs where the Cruze begins to get thrashy. Driven gently, the Cruze is one of the quieter cars I've had - the huge engine mounts probably help with that. Definitely way more refined than Chryslers 3.7 V6.
None of the 4 cylinders I've ever driven, BMWs included, can shake a stick at the 2 buttery smooth, quiet, and refined Toyota V6s I've had. But they sure get better gas mileage.
