Modern fames, particularly aluminum and carbon fibre generally have oversized and airfoil shaped tubes, which provide a lot more surface area for reverberation of sound waves. Drivetrain noise is more prominent. I don't recall this being as big issue on the Alan, so I think it's more a function of tube diameter and shape than material.

If you want a quiet drivetrain, don't clean your chain, cogs or chainrings. It's amazing how much a little dirty buildup dampens the sound.