Tuesday, November 28, 2006

The Microphone Part 2

The first Microphone was the Carbon Microphone. The word "microphone" comes from the Greek word "micro", which means "small", and another greek word "phone" that means "voice". It first appeared in a dictionary in 1683 as "an instrument by which small sounds are intensified". In this era the word was meant the acoustical hearing devices such as the ear trumpets and megaphones of that era. While Wheatstone was the first to use it in the electrical context, the word predates everything.

David Hughes was born in London in 1831 and grew up in the United States. He like Wheatstone was a musician. Hughes became a professor of music at St. Joseph's College in Bardstown, Kentucky, in 1850. He also developed an interest in electrical engineering and brought his two main interests together when he began studying the transmission and amplification of sound. Also similar to Wheatstone, his introduction to electronics revolved around the Telegraph. In 1855, David Hughes received his first U.S. patent for a printer used with a telegraph instrument. In 1857, Hughes returned to London and took his work with him.

In 1878, Davie-boy invented the carbon mic. Hughes was working on a telephone receiver and found this loose contact in a simple circuit made of a battery and a telephone receiver. He noticed the loose contact created a situation where sounds in the receiver matched the vibrations on the diaphragm of the telephone mouthpiece.

What makes this interesting is that Bell, the inventor of the telephone hated the battery. Mr.Bell did not want to use battery power in his telephone system at all. Many of his his early phones had no batteries but had great difficulty in receivinng the weak signals. If he had succeeded, Hughes would never met that loose wire. So many tinkerers were working on this faintmness problem at roughly the same time. Emile Berliner had a loose-contact metal-to-metal transmitter. At the same time Hughes was wiggling 'carbon rods, a man named Blake was workign with carbon blocks and Mr. Hunnings was pressing forward with a carbon-granule design. Interesting that both Berliner and Hughes used the term "microphone" to describe their transmitters... (diagram from http://www.doramusic.com/patentdetails.htm) THEY RULE!)

So anyway there's Hughes wiggling that wire. He was wiggling it and thinking about the shortcomings of Edison's carbon telephone transmitter. It was here that he realized that the arrangement was causing variable electrical resistance. The variation in resistance was such that it produced an exact representation of the sound waves as to height, length and form. He published the results in 1878 but refused to patent it!

Well-honored in his own lifetime, Hughes was the recipient of many honors and awards including a Fellowship of the Royal Society, a Grand Gold Medal in 1867, the Royal Society gold Medal in 1885, and The Albert Gold Medal, Society of Arts in 1897. It's no surprise I've written about him before.