Dynamic, or moving-coil microphones are the most common type. They use a small diaphragm and magnet to convert the sound waves to an electrical signal. This type is the most sturdy and ideal for hand-held use, however they only work effectively if used very close to the sound source (e.g. held very close to the mouth). They are also directional, which means they will only be effective if facing the sound source. Lastly, different models have set frequency responses, designed to be used for a specific purpose (e.g. vocal mic).