About Liquid Microphones and Their Functions

The history of liquid microphones traces back to the year 1876, when the first liquid transmitter was invented by Alexander Graham Bell and Elisha Gray at the same time. These transmitters later became the liquid microphones, which marked the beginning of all the telecommunication tools that have become an indispensable part of our lives now.

The transmitter consists of a mouth piece that is in the form of a funnel with a diaphragm connected to it. A metal pin is extended from the centre of the diaphragm to a metal cup containing diluted acid. This connection caused variations in the resistance levels when the pin was agitated by the movement of the diaphragm. The cup and pin components were attached to a battery and telephone receiver and sound reproduction occurred with clarity.

Elisha Gray was another scientist, experimenting with the liquid microphone system and her design had the presence of a conductive mobile rod, which was immersed in an acidic solution reproducing sound effectively.

In this model, another rod which was fixed in position besides the first one was attached to the battery. The variation in resistance here was due to the difference in sound pressure created by the movement of the two rods. The main difference between the two types of transmitters is the rod which is made of brass in case of the one invented by Elisha Gray while a needle was used in the other model.

This heralded the invention of more advanced models like the ones developed by Thomas Edison. But these were the first microphones that worked and even today the first conversation between Bell and Watson over the liquid microphones is remembered.

The modern version of liquid microphones was invented by David Edward Hughes. He conducted some truly remarkable experiments by mounting the liquid microphone on top of a sound box which had numerous insects inside. The gnawing sound of the insects was amplified by the phone. This had a concept similar to the magnification of small objects by a microscope.

The liquid microphone was later modified and perfected by scientists like Majoranna, Chambers, Sykes and Vanni. They tried the addition of water to the liquid used in the microphones. A reservoir containing conductive fluid was used in the microphone and Majoranna used a 780 watt voltage to activate the microphone.

High voltage microphones were later invented by C.Egner and J.G Holmstrom which had about 16 carbon units cooled with the help of water. Voltages ranged from 10 to 30 volts and the current from 20 to 10 amperes, for the connection of different types of units present.

The liquid microphones were thus transformed to more sophisticated versions. During the First World War and later on, they found immense use as public address systems and for broadcasting in television, films and radio stations.

source: The Microphone Book, Second Edition: From mono to stereo to surround - a guide to microphone design and application by John Eargle