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.
You can also place sound absorbing materials, like the insulation in your home, between the walls to cut down on the transmition of sound waves. Compared to light, sound waves travel relatively slowly. Because of this slowness in the movement of sound waves, your brain is able to help you locate the source of a sound. There is a measurable difference in the time it takes the sound to reach both of your ears. From this you can tell where the source is located. You can use sound to measure distances.