What type of signal does a microphone convert into an electrical signal?

A microphone primarily converts an acoustic signal into an electrical signal. Acoustic signals are sound waves produced by variations in atmospheric pressure, created when objects vibrate. When sound waves reach the microphone, it captures these vibrations and transforms them into electrical energy using various methods, such as dynamic, condenser, or ribbon technology. This conversion is fundamental to audio recording and transmission, allowing sound to be amplified or recorded.

Other types of signals mentioned in the options do not accurately represent what a microphone converts. For example, a digital signal implies a binary representation of data, which is not the role of a microphone. Similarly, a mechanical signal pertains to physical movements or forces, while a radio signal involves electromagnetic waves used for communication over distances. Therefore, the acoustic signal is the appropriate and correct choice in this context.