Stop reading for a moment and listen to the sounds around you. What did you hear? The whirr of a computer fan, people talking, 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 the sound is made, how it travels, and how it is detected and interpreted.