Trends in Technology: Microphones


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RCA 44A

RCA 44A


Microphones are, perhaps, one of the most taken-for-granted electrical devices ever developed for wide-spread use. They have been used to guide military troops in times of war, provide millions of play-by-play sports broadcasts, announce details of Presidential candidate races -- and Presidential passings, and for the transmission of trillions and trillions of telephone calls. Microphones have been used for Earth-to-space communications and Moon-to-Earth communications when Neil Armstrong first set foot on the Moon on July 20, 1969. Our world would certainly be a bit quieter and less informed if it weren't for the invention of the microphone. Throughout this article we will look at microphones of the past, present, and, with a bit of visionary imagination, the future. Because this publication is focused toward the radio broadcast industry, we will journey in that direction as well.

Past

A microphone is defined as an instrument capable of transforming sound waves into changes in electric currents or voltage as used in recording or transmitting sound. According to history, the term microphone was first coined by Sir Charles Wheatstone in 1827 and was used to describe a stethoscope-type device he had developed to amplify weak sounds. The word is Greek in origin with "micro" meaning small and "phon" meaning sound. In 1876 Emile Berliner invented a microphone that was used as a telephone voice transmitter. The patent rights to that invention were then sold to the Bell Telephone Company for $50,000.

RCA Model 77

RCA Model 77


Inventor David Hughes is credited with inventing the carbon microphone in 1878. Early carbon microphone development supported the telephone and broadcast industry through the first several decades of the 20th century. While carbon microphones were widely used in broadcasting until the late 1920s, they continued in use in the telephone industry up until the 1980s when the use of miniature electret condenser microphones began.

Ribbon microphones came into play in the 1920s when the RCA Company developed its first version known as the PB-31/PB-17. These were replaced with the Model 44A and then later an improved magnetic material brought about the Model 44-B/BX. Early ribbon microphones used field coils and permanent magnets. Later models used double ribbon elements. In later years, the RCA Model 77 ribbon microphone became the most popular model for recording and broadcast because of its smooth sound and directional pickup patterns. The company went on to produce many other ribbon microphone models that have to this day remained staples of the early broadcast and recording industries and are dearly cherished by collectors worldwide. RCA terminated production of their microphones in 1973. Ribbon microphones of various brands have enjoyed a recent revival in the vocal and instrument recording markets with over two dozen new models showing up in the past two years.

Western Electric Model 618-A

Western Electric Model 618-A


Over the expanse of time, dynamic microphone elements have become one of the more popular types. Invented in 1897 by Ernst Siemens, the first commercially available dynamic microphone was the Western Electric Model 618-A introduced in 1931, a mere nine months before the RCA 44A.

In 1964 Bell Laboratories was awarded a patent for their creation of the electret microphone. That technology allowed for the manufacture of microphones of greatly reduced size, lower cost, improved reliability, and much-improved frequency response. Improvements to electret condenser microphone technology occurred over the following decades. The two most popular microphone technologies in use today are dynamic and condenser.

-- continued on page 2



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