The Cuda: Changes
If you compare this new drive to the previous Seagate Barracuda drives, you will see that only few things that have been changed at the exterior. The most interesting difference is the metal cover at the bottom of the drive. It was part of the Barracuda ATA IV and was used to both protect the electronic components and absorb noise.
In terms of the new drive's acoustics, there is certainly no need to shield anything. Yet the protective function of the metal cover seems logical here. Perhaps cost considerations played a role in the decision to remove it.