Back in the day, before electronic gadgets, speakers, microphones and other modern audio visual solutions existed, performers relied on their own powerful lungs—with some help from the basic design and architecture of the performance hall—to carry their voices into the audience. Contemporary opera singers are still trained to project their voices without any voice amplification systems.
Source: AFSBOh Mic Goodness.
But not all performers have the abilities of a trained opera singer, nor do rock stars always perform in large concert halls. Bars and other common venues aren’t exactly built to accommodate acoustics. And that’s where the microphone and amplifier comes in.
Aside from being pretty good stage props that can help you fire up the crowd, the microphone is an essential piece of hardware for musicians, stage actors, and guest speakers. Invented in mid-1877 by Emile Berliner and Thomas Edison, the microphone is a type of transducer, which is—in simplest terms—an electronic device that you can get from electronic stores which turns one form of energy into another. Specifically, a microphone turns sound waves into electrical energy.
Microphones come in all shapes and sizes, from ribbon microphones used in older radio programs to the dynamic microphones used in just about every modern rock show. The one thing every microphone has in common is a diaphragm. Consisting of a thin piece of material, usually aluminum, plastic, or paper, the diaphragm vibrates when it’s hit by sound waves. The diaphragm then causes other parts of the microphone to vibrate, eventually turning your voice into electrical energy.
Of course, the average human can’t really hear electricity. The electrical energy travels from the microphone through cables and wires and eventually reaches the speaker. A speaker is just another transducer, albeit with the opposite task of turning electrical energy back into sound for adoring fans to digest through their ear holes.
Mic Problems are Your Problems
Microphones are a technological innovation that is essential to recording music and firing up the audience, but they’re not without problems.
The most common problem is feedback, characterized by the high-pitched squeals, howls, and distortion that aren’t usually very pleasant to the ears. When a microphone feeds an audio signal into the system, the speaker output should launch the sound out into the crowd. Feedback occurs when that signal goes from the speaker back into the microphone….which then gets sent back out the speaker and into the microphone. That cycle continues, creating those un-enjoyable sounds until you break the cycle, usually by turning the mic or the speakers off.
However, some artists have actually used feedback to their advantage, which is why you sometimes see guitarists holding up their guitars to speakers.
Acoustic phase interference occurs when you use more than one microphone at once, like if you were a college professor and had two microphones at your lectern. Because of the mic placement, your voice will reach the microphones at different times. Mixing these outputs together often results in feedback and poor audio quality. Switching to just one mic is usually enough to eliminate the problem.
Remember that the mic is only as good as the person speaking or singing into it. With plenty of practice, you should have no problem producing a solid sound.