Chapter 18

Loudspeakers and Earphones

Loudspeakers are the opposite of microphones, converting electricity into equivalent acoustic energy. Even though they serve opposite purposes, many of the same technologies are used. For example, most loudspeakers use electromagnetic force to move a coil of wire back and forth inside a magnetic field. A cone made of paper or plastic is attached to the coil, and the cone increases and decreases the surrounding air pressure to create sound. This is very similar to the coil, magnet, and diaphragm of a dynamic microphone. Indeed, a dynamic microphone can function as a loudspeaker, and vice versa. Other speaker designs are based on an electrostatic principle, much like condenser mics. Piezoelectric elements are ...

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