Many dentists use air-driven "hand-pieces" (the dental term for "drills"). While acceptable for many procedures, these "whiney sounding" air powered hand pieces all have a degree of non-concentricity; they do not rotate perfectly smoothly.
For the most precise aspects of restorative procedures, we use electric hand-pieces. This results in extraordinarily precise interfaces between your tooth and your new restoration (crown, veneer, or filling). This will bring more comfort to you as well. With a more precise tool, there is less vibration and less noise!