History of Carbon, Condenser And Ribbon Microphones Used For Sound Recording And Telephone

My last article, which received tremendous interest, was on the History of Audio Recording. I am grateful to all of you that read it and made it a great success. This article is no less important. We certainly can’t discuss the History of Audio Recording without also discussing the History of the Microphone. Neither can exist without the other. Together, let’s explore the birth and development of this incredible invention.

A microphone is, simply stated, a device that captures “waves” in the air created by the voice or any other noise transmitter and translates those waves into electrical signals. Another way to say it is to convert acoustic power into electrical power. After the sound waves are converted into electrical signals, to hear them again in an acoustic setting, they must be converted back to acoustic power through some kind of loudspeaker. It is amazing to think with all the technological advancements in the last 40 years, we still use this simple process on our stereo, computer or ipod.

Have you attended a concert lately? The relatively weak signal from a voice or musical instrument is created, changed into electrical energy by some sort of microphone, boosted through a series of power amplifiers and, finally, converted back to acoustic energy through loudspeakers. It is easy to sit, enjoy the music, and forget to be thankful for this amazing power that was created in our universe which we enjoy our entire day.

Let’s meet some of the visionary people who discovered and developed the universal principles that created a microphone.

Johann Phillip Reis (1834-1874)

This German physicist designed a “sound transmitter” that employed the use of a metallic strip that rested on a membrane with a metal point contact that would complete a circuit as the membrane vibrated. His basic belief that, as the membrane responded to the increase and decrease of acoustic energy and bounced the metal point up and down with more intensity and increased the amplitude of electrical current, was brilliant. Unfortunately, this early effort was not developed enough to produce speech that could be understood.

Elisha Gray (1835-1901)

This American inventor would one day become one of the founders of the Western Electric Company. Gray’s design was called a “liquid Transmitter”. The “liquid” was an “acidic” solution. This was an incredible innovation. A diaphragm was attached to a movable electrically conductive rod that was immersed in the acidic solution. A second rod was fixed. With a battery attached, a circuit could be completed between the two rods. Acoustic vibrations traveling through the diaphragm caused the distance between the two rods to vary. The result was that this variance produced corresponding changes in electrical resistance in the acidic cell, changing the levels of current. These variations could be translated to a week audible sound.

Alexander Graham Bell (1847-1922)

Famous for his development of the telephone, he employed a similar device as Gray to produce the first transmission of intelligible speech over his primitive telephone. Most of us have heard of the famous words of Bell to his assistant, “Mr. Watson, come here. I want you.” The true inventor of the telephone, though, became a legal dispute between Bell and Gray. The courts remained neutral regarding their claims due to the overall poor quality of these early devices.

David Edward Hughes(1831-1900)

While Bell and Gray slugged it out in the courts, Hughes was diligently working to produce the first working microphone. Already a pioneer and patent holder in the telegraph industry by 1855, he designed a new kind of microphone by 1878. It was a completely different design that Bell and Gray. It incorporated the use of carbon granules loosely packed into an enclosed space. When the acoustical pressure varied as they traveled through the diaphragm, the electrical resistance that traveled through the carbon granules changed proportionally. The resulting sound was noisy and full of distortion but it was a significant step forward. Since early reports in the newspaper compared his device with a microscope, ” it acts for the ear much in the same way that the microscope serves the eye,” Hughes coined the current name “microphone” to his invention. For more details, please visit these sites:- www.bunnydirectories.com

Thomas Alva Edison (1847-1931)

Edison took Hughes design and made it simple, cheap to manufacture, efficient and durable. He created a cavity filled with granules or carbonized anthracite coal packed between two electrodes, one of which was attached to a thin iron diaphragm. His refinements became the basis for all the telephone transmitters used in most of the telephones for the last century. Further, Bell Telephone and Bell laboratories are still incredible companies that continue to produce new communication technologies.

With the invention of the radio, new broadcasting microphones, like the Ribbon Microphone in 1942, were invented. The Ribbon Microphone originally employed the use of an aluminum ribbon that was placed between two poles of a magnet to generate voltages by electromagnetic induction. As the sound wave caused the ribbon to move, the induced current in the ribbon was proportional to the particle velocity in the sound wave. Ribbon microphones have historically been delicate and expensive. Today’s modern materials make present-day ribbon microphones durable enough for loud rock music and stage use.


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