The primary responsibilities of human resources are: 1  C - Compensation. 2  H - Human resource development. 3  E - Employee and labor relations. 4  S - Safety and health. 5  S - Staff.
A new technique uses sound waves to levitate objects and move them in mid-air. Credit: Dimos Poulikakos View full size image. View full size image. Hold on to your wand, Harry Potter: Science has outdone even your best Leviosa! levitation spell.
Let's contrast that with a mechanical wave. A mechanical wave involves the transfer of mechanical energy into and through a medium. Sound waves (which travel through air) and water waves (which move through water) are mechanical waves. They cannot travel without a medium through which to move. 11 people found this useful.