Microphones are used to capture sounds. They detect vibrations in the air caused by sound waves and convert these into electrical signals, These electrical signals are then passed on to be stored (in the process of recording), or fed to loudspeakers (which convert the electrical signals back into soundwave vibrations).
There are many different types of microphone, which come in many shapes and sizes, and they often use slightly different technologies. Powered ‘condenser microphones’ and unpowered ‘dynamic microphones’ are the most common types. With condenser microphones being the more sensitive of the two.
Special tools are also available to record sounds that travel through liquids and through solids. Hydrophones can record sounds that travel through liquids and are used to record underwater sounds. While contact microphones are able to detect soundwaves that pass through solid objects.