Sound: More Than What You Hear

Sound is a sensation that we hear. A sound originates in the vibration of an object. This vibration, in turn, makes the air or some other substance surrounding the object vibrate. The vibrations in the substance travel as waves, moving outward from the object in all directions. When the waves enter our ears, our organs of hearing translate them into nerve impulses. The impulses travel to the brain, which interprets them as a sound. The …

…oise cancellation (ANC) and active structural-acoustic control (ASAC). In the simplest form of ANC, a speaker produces sound waves that interfere destructively with the waves of an unwanted sound. As a result, the sound from the speaker cancels out the unwanted sound. In ASAC, a device called an actuator applies force to an object whose vibration is producing an unwanted sound. The force changes the nature of the vibration, making the resulting sound less objectionable.