Microphone sound expansion principle to explain

Amplifiers are electronic components we use, it is capable of magnifying the voice, let more people hear. That loudspeaker sound principle is what?

Microphone to receive incoming signals. after a combination of electronic components. the signal amplification. as a result of signal amplification of power crystals. through the speakers emit sound. the action principle is sound signal converter converts the electrical signal. Speakers for voice output of the important components of electronic products, its wide range of applications, can be installed in various types of headphones or machine, such as Walkman, stereo, radio communications, multi-media computers, records or electronic dictionary, used to listen to sounds and music, also can be installed in the telephone automatically dials, used to call.