A microphone is a device made to capture waves in air, water or hard material and translate them into an electrical signal. The most common method is via a thin membrane producing some proportional electrical signal. Most microphones in use today for audio use electromagnetic generation are dynamic microphones, capacitance change condenser microphones or piezoelectric generation to produce the signal from mechanical vibration.

Uses of different kinds of microphones

Condenser microphones span the range from cheap instruments to high quality instruments. They generally produce a high quality audio signal and are now the popular choice in laboratory and studio recording applications. They require a power source, provided generally from microphone inputs from a small battery.

Professional microphones often sport an external power supply for reasons of quality perception. Power is necessary for establishing the capacitor plate voltage, and is also needed for internal amplification of the signal to a useful output level. Condenser microphones are also available with two diaphragms, the signals from which can be electrically connected such as to provide a range of polar patterns such as cardioid and omnidirectional.

Carbon microphone, formerly used in telephone handsets, is a capsule containing carbon granules pressed between two metal plates. The carbon microphone can also be used as a type of amplifier, using a small amount of sound energy to produce a larger amount of electric energy. Carbon microphones were used as early telephone repeaters, making long distance phone calls possible in the era before vacuum tubes.

Crystal microphones used to be commonly supplied with vacuum tube or valve equipment such as domestic tape recorders. Their high output impedance matched well to the high input impedance of the vacuum tube input stage. They were difficult to match to early transistor equipments and were quickly supplemented by dynamic microphones for a short while, and later small eletret condenser devices. The high impedance of the crystal microphone made it very susceptable to handling noise, partly from the microphone itself, but also from handling of the connecting cable.

Shotgun microphones are high directional microphones. They have small lobes of sensitivity to the left, right, and rear but are significantly more sensitive to the front. This results from placing the elements inside a tube with slots cut along the side and wave cancellation eliminates most of the off axis noise. Shotgun microphones are commonly used on TV and film sets, and for field recording of wildlife.

Conclusion

The microphone is a ubiquitous piece of equipment and comes in a number of models. Found in everything from telephones to computers to recording studios, microphones are part of our daily life. It is perhaps the most critical part of the audio chain. A good quality microphone will provide the basis for excellent audio, whereas a poor quality will mean poor quality audio, no matter how good the rest of the system is.