The introduction of the crystal microphone created a new era of cheap better quality microphones. Astatic Corporation began when two Ham Radio enthusiasts, C. M. Chorpening and F. H. Woodworth, found that they could make a microphone out of Rochelle salts. Rochelle salts are one of three different salts found in household Cream of Tarter. It has the strange ability to squirt out an electric current when you bend a crystal. This is called the piezoelectric effect. The trick is to bend the crystal without cracking it.
Chorpening and Woodworth took a thin piece of Rochelle salt and placed it so that an armature could push on the ends of the crystal causing it to bend on a fulcrum....
The fiber optical microphone is an entirely new microphone concept, first invented in Israel in 1984 by Drs. Alexander Paritsky and Alexander Kots. Conversion of acoustical waves into electrical signals is achieved not by sensing changes in capacitance or magnetic fields (as with conventional microphones), but instead by sensing changes in light intensity. During operation, light from a laser source travels through an optical fiber to illuminate the surface of a tiny, sound-sensitive reflective diaphragm. Sound causes the diaphragm to vibrate, thereby minutely changing the intensity of the light it reflects. The modulated light is then transmitted over a second optical fiber to a photo detector, which transforms the intensity-modulated light into electrical signals for audio transmission or recording.
The fiber optical microphone has very specific advantages over conventional microphones. First, no electronic or metal components are used in the microphone head or the connecting fibers, so the microphone does not react to or influence any electrical, magnetic, electrostatic or radioactive fields (this is called EMI/RFI immunity). The fiber optical microphone is therefore ideal for use in areas where conventional microphones are ineffective or dangerous, such as inside industrial turbines or in magnetic resonance imaging (MRI) equipment environments. Another advantage is the physical nature of optical fiber light propagation. The distance between the microphone's light source and its photo detector may be up to several kilometers without need for any preamplifier and/or other electrical device. Finally, fiber optical microphones possess high dynamic and frequency range, similar to the best high fidelity conventional microphones. They are robust, resistant to environmental changes in heat and moisture, and are excellent for noise-canceling applications....
Carbon mics worked because the sound energy vibrated the carbon particles pushing them together and making the capsule a better or worse conductor of electricity. By forcing a small current through the carbon, the electric flow could be broken up by the effect of sound on the carbon. Carbon microphones were cheap and durable.
A carbon microphone, formerly used in telephone handsets, is a capsule containing carbon granules pressed between two metal plates. Their problem was that they did not have a very good frequency response. The carbon particles did not respond well to higher frequencies, and the low notes did not have enough energy to compress the particles to make a good connection. Carbon microphones have extremely low-quality sound reproduction and a very limited frequency response range, but are very robust devices. Carbon mics aren’t good for recording music....
A microphone sometimes referred to as a mike or mic, is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. Microphones are transducers which detect sound waves and produce an electrical image of the sound; they produce a voltage or a current which is proportional to the sound signal. They were first used with early telephones and then radio transmitters and have evolved through a number of major changes to the high quality instruments of today....
