Stop reading for a moment and listen to the sounds around you. What did you hear? People talking, a cat padding on the floor, the noise of cars going by? When scientists want to understand more about how sound moves and behaves, they study acoustics [Ah-KOO-stix].
When you drop a rock into a pond, you can see waves move across the surface, away from the rock. The sounds that you hear are also made of waves, except that sound waves can travel through air or through solids. In fact, sound waves travel faster in solids like wood or plastic than they do in the air.
Think about the sound made by a guitar. When a person strums a guitar string, the air around it begins to vibrate. This vibration moves through the air as a wave, and it can bounce off walls (which can cause an echo) or be absorbed by other materials. It can also go into your ear, which will send a signal to your brain. Your brain interprets the wave as the sound of a guitar.
Understanding sound waves is important for many fields. Doctors use ultrasound waves, which are so highly pitched that we can’t hear them, to see inside the human body. When an architect designs a concert hall, he or she must think about how the sound waves travel through the air to make sure everyone hears the same sounds. Sound waves can also be used to detect objects that are underwater, like fish or submarines, with a technique called sonar: sound waves are sent out through the water from a source, and the object reflects waves back to the original source of the sound waves called a transmitter.
Scientists who study acoustics try to understand all the parts of sound: how it’s made, how it travels, and how it’s detected and interpreted.
acoustics: The science of sound.
echo: To bounce back. For example, sound bouncing off walls of a tunnel, and returning to their source. Radio waves emitted above the surface can also bounce off the bedrock underneath an ice sheet — then return to the surface. Or ideas or events that seem to reflect one or more others, as a reverberating sound might.
field: An area of study, as in: Her field of research is biology. Also a term to describe a real-world environment in which some research is conducted, such as at sea, in a forest, on a mountaintop or on a city street. It is the opposite of an artificial setting, such as a research laboratory. (in physics) A region in space where certain physical effects operate, such as magnetism (created by a magnetic field), gravity (by a gravitational field), mass (by a Higgs field) or electricity (by an electrical field).
plastic: Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation. (adj.) A material that is able to adapt by changing shape or possibly even changing its function.
sound wave: A wave that transmits sound. Sound waves have alternating swaths of high and low pressure.
submarine: A term for beneath the oceans. (in transportation) A ship designed to move through the oceans, totally submerged. Such ships — especially those used in research — are also known as submersibles.
vibrate: To rhythmically shake or to move continuously and rapidly back and forth.
wave: A disturbance or variation that travels through space and matter in a regular, oscillating fashion.
wood: A porous and fibrous structural tissue found in the stems and roots of trees, shrubs and other woody plants.