h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

INTRODUCTION

What is a microphone? How does it work? Where does it come from, and how does it effect society today? The microphone is a device that has undergone drastic changes in a relatively short period of time, and is taken for granted by most people on a daily basis. They are now so common and reliable, they are frequently overlooked. It is the goal of entry answer these questions, and to examine the microphone’s impact on our lives, and on society.


BODY

A microphone is a transducer, a device capable of converting energy from one form to another. By transmitting a varying value down a transmission line, sounds can be reproduced. Today, microphones use many different techniques to achieve this, from changing values in voltage to changes in resistances, but the concept remains the same. By vibrating a diaphragm, with our voice, for example, some electrical value is altered, and by transmitting the changes of that value, we can transmit sound.

On the other end, using a voice coil, a braided wire wrapped around a magnet, we once again create a transducer that this time changes analogous voltages into magnetic force, a by-product of which is actual physical force. By using the “paper” or cone of a speaker to harness this force, we cause the compression and rarefaction of air molecules, the same mechanism used in the transmission of sound through the air. Both the diaphragm of a microphone and the voice coil of a speaker are controlled by the electrical laws that govern inductors.

The energy of sound waves move a diaphragm inside the microphone capsule. This is typically connected to a coil of wire positioned around a magnetic source. As the diaphragm moves the coil back and forth, it cuts through magnetic lines of force, thereby generating a current that is directly proportional to the sound that moves the diaphragm. The design of current microphones in use today range from vintage audio pieces such as ceramic, carbon, and dynamic microphones, to large diaphragm condenser microphones, ribbon, electret condenser, boundary layer, even piezoelectric, or crystal, microphones that have a diaphragm connected to a crystal. As the crystal is deformed, or shock excited, it produces a voltage. This just scratches the surface of today’s microphone technology. The science and technology is beyond the scope of this paper. It is mentioned to simply indicate the incredible range, or different “flavors”, of microphones in existence today, each of which is suited to it’s own particular task.
The origin of the microphone is somewhat shrouded in mystery, and is a convoluted path to trace, considering the fact that several independent inventors all had similar concepts at roughly the same time.

The concept of the microphone can be directly traced back to Charles Bourseul, who was first inspired to electrically transmit the human voice in an attempt to improve the telegraphy system of his time, pioneered by Samuel Morse. However, while his concept was fairly close to the microphone of later generations, attempts to convert the resultant changes in current back into soundwaves failed. Still, his thesis on the electrical transmission of sound was published in “L’Illustration de Paris” in 1854.

Although Philip Reis and Alexander Bell can be credited with the first pedestrian microphone, patented on February 14th of 1876, and later demonstrated at the World Exhibition in Philadelphia later that year, they would later acknowledge the work of Bourseul as a major contribution to their discovery.

Bell’s first microphone was funnel-shaped, and the diaphragm membrane was connected to a rotor. The rotor in turn was connected to a coil, which would induce a voltage. When Bell offered to sell his patent to the Western Telegraph Company in 1877 for $100,000, “…the response was ‘What shall we do with a toy like that?’….later the same company offered him $25,000,000 for his patent, but this time Bell was the one to refuse the offer.”

The methods of modulation used in microphones today are far from the original concept that Elisha Grey, founder of American Telephone and Telegraph Company, had when he developed the carbon microphone, later improved upon by David Edward Hughes in 1878. Originally, the carbon microphone had a diaphragm adjacent to granulated carbon. The speaker’s voice would strike the diaphragm, thereby moving the carbon granules, through which a current was being passed. Variations in the current corresponded to the sound pressure striking the diaphragm. This is archaic even by the standards of today’s carbon microphones, which appear around us everywhere.

The carbon microphone of today was once widely used in telephones, which connected the country, and eventually the world, with an easily accessible communications network. The customary condenser microphones have now generally replaced these. Also, used in radio broadcast for many years at the turn of the century, carbon microphones were commonly used in fast-food drive-thru’s. Because speakers and microphones act on the same principle, for many years the speaker you heard the order taker on acted as a microphone to relay your order back to the store. This process actually works, albeit not very well. If you’re interested, try plugging your headphones into a microphone jack, and record yourself talking into the speaker of the headphones, then play it back to hear how it sounds. It makes a rough, but effective recording. It’s no wonder that fast-food restaurants are notorious for misunderstandings in the drive-thru line, but even stranger is the fact that as technology has improved, and the presence of both a microphone and a speaker on each end have replaced this archaic system, the communication has not been noticeably improved.

An important footnote to the history of the microphone is that in 1877 Thomas Alva Edison made the first recording of sound, on his ingenious wax cylinder device, to record himself singing “Mary Had a Little Lamb”. This is more remarkable when we consider that the device itself required no electricity. It was powered solely by acoustical and mechanical energy. It’s microphone consists simply of a large horn for the compression and focusing of soundwaves, and contains a thin, pliable sheet of material at the bottom with a knife-shaped stylus inserted in the center. As sound travels down the horn, it moves the pin that carves the wax cylinder as it rotates in the machine. Ironically, musicians had to place themselves around the horn at different distances to achieve the clearest recording, unlike the microphone placement techniques used in recording today.

Today, microphones have hundreds of practical applications, from in-house communication systems in schools to the public address systems used by orators, musicians, and anyone wishing to be heard by large groups of people.

Microphones are finding even more unconventional uses in our society. In the Broadway run of the show “Bring in ‘Da Noise, Bring in ‘Da Funk”, amazingly unusual microphone techniques were used to deliver the unique flavor of tap the show’s designers and choreographers were looking for. After lengthy experimentation, they added Sennheiser Red Dot model microphones to each dancer’s shoes, secured by velcro to the laces, and secured to the dancer’s ankles by straps. These wireless microphones helped project the sound of the dancing, which was just as integral to the show as the traditional role the music takes, in part due to the percussive nature of tap dancing. Thanks to the velcro, quick changes of shoes required by the show could be accomplished quickly, and in one number onstage, without difficult rearrangement of the microphones. The lead dancer required Sennheiser Blue Dots, identical to the Red Dot model but with a –50 dB pad because of the force with which Savion Glover dances. Other microphone “extras” for the show included supplementary pressure zone microphones and C:ducer microphones mounted under a specially constructed “tap-friendly maple stage deck”, which would be secured to the stage in a manner that rendered the microphones inaccessible should they be needed for maintenance or other adjustment. In all, 58 stereo microphone inputs were used just for the dancer’s shoes, in addition to the normal assortment of vocal and foot mikes.

Theater and communication are not the only areas of our lives to be touched by this useful tool. Law enforcement is rife with use of the microphone, from the wire-tapping exploits of Linda Tripp to the shotgun mics used to film the wildly successful television show COPS. The phrase “he’s wearing a wire” is ingrained in our society, stemming from the occurrence of informants trying to capture shady individuals breaking the law by wearing small, concealed microphones. And as the size of these microphones become smaller and smaller, detection of them becomes more difficult as well. On a daily basis, new precedents regarding the use of microphones, and their results being used as evidence in legal trials, are being written not just across our country, but around the world.


CONCLUSION

The microphone has innumerable uses, from personal tape recorders for to microphones which allow us to discuss our opinions with others by telephone, by amateur radio, and now even via the internet. The positive possibilities of a microphone are unlimited, and as with any technology, it’s misuses are just numerous. The good or harm generated by this item falls to us, the end-user. I hope that it, as with all technologies, will be used for constructive, rather than destructive purposes.