What converts an electrical signal back into sound energy?

The function of converting electrical signals back into sound energy is primarily performed by a speaker or headset. These devices take the electrical signals produced by audio sources and convert them into sound waves that we can hear. This process involves the movement of diaphragms within the speaker or headset, which vibrate in response to the electrical signals, creating variations in air pressure that produce sound.

An amplifier is responsible for increasing the strength of an electrical signal but does not convert it into sound. A receiver processes signals, often for radio communication, but does not directly translate electrical signals into sound. A microphone, on the other hand, works in the opposite direction by converting sound waves into electrical signals for transmission or recording. Thus, the role of the speaker or headset is integral to the audio experience, making it the correct answer.