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.
Basics of Sound. Sound is a vibration, or wave, that travels through matter (solid, liquid, or gas) and can be heard. How does sound move or propagate? The vibration is started by some mechanical movement, such as someone plucking a guitar string or knocking on a door.