Friday, December 08, 2006

The Microphone part 10

These are the contenders. The ones that had good ideas, put it to paper (usually) but never followed through. Mics that didn't happen, and are relegated to the footnotes. Here are three people and two mics that didn't make the cut.

1. M. Charles Bourseul
In 1854 Chuck published a plan for conveying sounds and even speech by electricity. "Suppose, that a man speaks near a movable disc sufficiently flexible to lose none of the vibrations of the voice; that this disc alternately makes and breaks the currents from a battery: you may have at a distance another disc which will simultaneously execute the same vibrations." He claimed to have performed experiemnts to support this, but I got nada. So far, just a big talker.

2. Johann Philipp Reis
In 1860 Johann Philipp Reis produced a device which could transmit musical notes, and even a lisping word or two. The Reis transmitter was a "make-break" transmitter. A make-or-break signaling was able to transmit tones, and some vowels, but since it did not follow the analog shape of the sound wave it could not transmit complex sounds like consonants. The Reis transmitter was very difficult to operate, since the relative position of the needle and the contact were critical to the device's operation at all. Eventually he did figure out how to vary current, but by then the only people who thought he was the first were his fellow Fermans.

3. Poul LaCour
Around 1874 Poul la Cour, a Danish inventor, experimented with audio telegraphs on a line of telegraph between Copenhagen and Fredericia in Jutland. In this experiment a vibrating tuning-fork interrupted the current, which, after traversing the line, passed through an electromagnet, and attracted the limbs of another fork, making it strike a note like the transmitting fork. LaCour did not transmit voice, only pure tones like Reis. Later on he did far more useful stuff with wind turbines.

4. High voltage mics
Around 1900 many wireless experimenters came up with owrking high-power microphones. The upside was greater sensitivity and amplification. the down side is that they were very hot and required cooling. Like engines of the era the options were air-cooled, and water cooled. Berliner made one carbon mic model with a high-current carbon microphone that was air cooled by a fan mounted under the microphone. The motor sound was very audible over voice in use! Toward the end of 1906 Fessenden had built a high-power microphone. This microphone could handle up to 15 amperes of current without burning up, a major step-forward. This carbon mic was water-cooled, but required so much water circulation he called it a "trough-type." There were of course workable water-cooled mics later.

5. Open Flame Microphone.
In 1902 and 1910 Blondell and Chambers developed flame microphones. Yes, there was actual fire involved. Blondell's "flame controller" worked as follows: Two spark rods are seet up in an oscillating circuit adjusted just short of sparking. One Flame is adjusted to reach up to the gap. By speaking into mouthpiece the diaphragm vibrates and alters the pressure of the gas entering the circuit. This causes the flame to change its length. As the flame varies its entrance into the gap,the resistance between the gap points varies, and sparking occurs in response to its movements. ...

Next week, no more microphones!