Why Are Microphones Called Microphones?

Microphones are everywhere in our lives: at music concerts and live speaking events, in our phones, computers, and intercom systems. They've been called microphones for a long time. As silly a question as it may be, I figured I'd explain why in this article!

So why are microphones called microphones? The term ‘microphone' can be broken into ‘micro' and ‘phone.' Micro (from Greek mikros) means “small,” and phone (from Greek phone) means “sound” or “voice.” Microphone translates to “small sound,” which is accurate, as the microphone deals with small audio signals.

Let's discuss the term microphone and how it came about in this brief article.

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Why Are Microphones Called Microphones?

So we've discussed the derivation of the word microphone: micro means “small” and phone means “sound.” Therefore microphone directly translates to “small sound.” Let's expand on this idea.

Are microphones really small sound? Well, no, they're not literally small amounts of sound. But they do deal with small amounts of sound.

Microphones are transducers of energy. They change mechanical wave energy (sound) into electrical energy (audio signal).

Microphones capture loud sounds accurately. Some dynamic microphones are capable of recreating sound so loud that they don't even have a maximum sound pressure level value. However, the electrical signal voltage produced by microphones is relatively small to other audio signals.

So the microphones change sound energy into a low-level audio signal. In other words, microphones output a “small sound.”

To learn more about microphones and their role as transducers, check out my articles How Do Microphones Work? (A Helpful Illustrated Guide) and Microphone Types: The 2 Primary Transducer Types + 5 Subtypes.

How Micro?

A typical passive professional microphone has a sensitivity rating of 1-4 mV/Pa (@ 1,000 Hz). That's 1 to 4 millivolts per 1 pascal of pressure (at a reference tone of 1,000 Hz).

1 Pascal is equal to 94 dB SPL (decibels sound pressure level).

The measurement of Pascals, in this case, is not absolute pressure. The standard atmospheric pressure is 101,325 Pascals. The Pascal values related to sound are the variations from standard (average) pressure caused by sound waves. 

Decibels are logarithmic. Every doubling of the sound pressure level is equal to an additional 6 dB. However, voltage and pressure are linear.

Let's say a microphone outputs 2 mV/Pa. We would see the following input/output values:

• 64 dB SPL = 0.03125 Pascal = 0.0625 millivolt output convcersational speech at 1 meter distance
• 70 dB SPL = 0.0625 Pascal = 0.125 millivolt output
• 76 dB SPL = 0.125 Pascal = 0.25 millivolt output
• 82 dB SPL = 0.25 Pascal = 0.5 millivolt output
• 88 dB SPL = 0.5 Pascal = 1 millivolt output
• 94 dB SPL = 1 Pascal = 2 millivolts output
• 100 dB SPL = 2 Pascal = 4 millivolts output
• 106 dB SPL = 4 Pascal = 8 millivolts output
• 112 dB SPL = 8 Pascal = 16 millivolts output
• 118 dB SPL = 16 Pascal = 32 millivolts output
• 124 dB SPL = 32 Pascal = 64 millivolts output
• 130 dB SPL = 64 Pascal = 128 millivolts output commonly referred to as the threshold of pain

These output voltages are relatively small. For example, in order to drive a loudspeaker to produce 124 dB SPL, we'd need much more than a 64 mV AC voltage.

Decibels can be confusing to understand. For more information, check out my article What Are Decibels? The Ultimate dB Guide For Audio & Sound.

Mic Level Versus Line Level

Mic level and Line level are two common standards for nominal voltage levels. Both these levels are in reference to the voltage of an audio signal.

Note that mic and line levels are merely specified as averages and are not absolutes (much like microphones don't only produce one level of output voltage). These levels are useful to understand when dealing with audio signal flow between various pieces of gear.

• Mic level is typically specified between −60 dBu and −40 dBu where 0 dBu = 0.775 volts.
• Line level is professionally specified as +4 dBu.
• To confuse things, consumer-grade line level is given as −10 dBV  where 0 dBV = 1 volt. We won't talk about consumer-grade.

At a nominal +4 dBu, line level is the level of a signal that travels through mixing consoles and recording systems. Line level is sent to the power amplifiers that power loudspeakers and studio monitors (speakers need “speaker level” signals, which are even stronger than line level signals).

At +4 dBu, the voltage is roughly 159 times that at −40 dBu and 1585 times that at −60 dBu (mic levels). As you can see, mic (microphone) level is very small!

In general, we may think of line level as being 1000 times stronger than mic level.

Mic level is the signal produced by a microphone. 

Passive microphones (those without built-in active amplification) generally have sensitivity ratings between 1-4 mV/Pa. Active microphones can have a sensitivity rating upwards of 32 mV/Pa. Of course, microphones will accurately reproduce much higher sound pressure levels than 1 Pascal, so sensitivity isn't a great measurement of mic level.

The Neumann U87 is a famous active microphone capable of −6dBu maximum output voltage. This is considered an extremely high mic level. This level of signal would not need much amplification to bring it up to line level. However, the point is it's still smaller than the nominal line level!

To learn more about microphone output signals, check out my articles What Is A Microphone Audio Signal, Electrically Speaking? and Do Microphones Output Mic, Line, Or Instrument Level Signals?

This is one way of considering the term microphone (“small sound”).

Yet another, perhaps stronger, consideration is to look through history…

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A Brief History Of The Microphone

The term microphone was coined in 1827 by Sir Charles Wheatstone, an English scientist and inventor.

Charles Wheatstone's microphone was an instrument for augmenting feeble sounds. This “microphone” resembled a physician's stethoscope. However, rather than pneumatic tubes carrying the sound from a diaphragm to an earpiece, Wheatstone's invention used solid metal rods. This invention was prompted, in part, by the fact that sound travels much faster through solids than through air.

This instrument is not at all what our modern microphone has come to be. However, this initial invention of the microphone does fit the name well. It deals with the augmentation and transfer of small sounds.

Half a century later, the term microphone would resurface, approximating a closer design to current microphones.

The Telephone And Liquid Transmitter

The earliest forms of the modern microphone coincided with the invention of the telephone. Though still controversial, Alexander Graham Bell is credited with the invention of the telephone (and microphone) in 1876. At its inception, the telephone (microphone) was deemed the “liquid transmitter.”

The liquid transmitter had a mouthpiece that leads sound waves through a tube to a membrane (diaphragm). This membrane moved according to the sound waves and had a small wire attached to it. This wire dipped into a conductive liquid (acid solution) within a container.

A battery was positioned outside the container, and fed electricity to a brass rod dipped into the liquid. 

As the membrane moved, the voltage of its attached wire changed. This voltage was sent along another conductive wire out to an electromagnet, which caused a similar vibration in a secondary membrane (speaker), reproducing a close resemblance of the original membrane's vibration.

This is very similar to our modern-day microphone but was not called the microphone just yet.

The Carbon Microphone And ‘Microphone' As A Modern Term

Though U.S inventor Thomas Edison was awarded the patent for this original microphone, historians mostly agree that the English inventor David Edward Hughes invented the carbon microphone in 1878.

Hughes apparently also coined the term “microphone” for this invention. Before Hughes brought forth the “microphone,” these devices were simply referred to as “transmitters.”

One could see how this terminology could get confusing with the other contemporary inventions at the time.

Hughes' carbon microphone, as the name suggests, used loosely packed carbon granules.

The diaphragm, much like modern mic diaphragms and like the membrane of the liquid transmitter, vibrated following the varying sound pressure waves around it.

This caused varying pressure on the carbon granules, resulting in a proportionate variance in the resistance of the carbon. This proportionality allowed for a reproduction of the sound waves as an electrical signal.

The accuracy of the carbon microphone was excellent when compared with that of the liquid transmitter.

So from a historical sense, the term microphone was coined by David Edward Hughes. This idea of a transducer converting acoustic sound waves into electrical signals has been greatly improved upon over time.

So even though our modern microphones are of far better design than the original carbon microphone, the name has stuck because the essence of the idea has remained consistent.

For a detailed read on microphone history, check out my article Mic History: Who Invented Each Type Of Microphone And When?

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Naming Common Transducer Principles And Diaphragm Types

There are 4 common types of microphones on the market today:

1. Dynamic moving-coil microphones
2. Dynamic ribbon microphones
3. True condenser microphones
4. Electret condenser microphones

Let's briefly discuss their names:

Dynamic Moving-Coil Microphones

Dynamic transducer types work on the principle of electromagnetism. Their capsules are based on the old technology of the dynamo. Hence the name dynamic.

Moving-coil dynamic mics are named as such because there is a coil of conductive wire attached to their diaphragms. As the diaphragm moves in reaction to sound waves, the coil moves with it. Hence the name moving-coil.

For more information on moving-coil dynamic mics, check out my article Moving-Coil Dynamic Microphones: The In-Depth Guide.

Dynamic Ribbon Microphones

Ribbon mics also work on the “dynamic” principle of electromagnetism.

They are called ribbon microphones because their conductive diaphragms look like thin ribbons.

For more information on dynamic ribbon mics, check out my article Dynamic Ribbon Microphones: The In-Depth Guide.

Electret Condenser Microphones

Condenser transducer types have capsules that are essential capacitors. Capacitors used to be called condensers. Hence the name condenser.

Condenser microphone capsules need a charging voltage to function properly. Electret material supplies a quasi-permanent voltage across the mic capsule. Hence the name electret.

Note that electret microphones require DC biasing to power their FET impedance converters properly.

To learn more about FETs and microphones, check out my articles What Are FETs & What Is Their Role In Microphone Design? and Do All Microphones Have Transformers And Transistors? (+ Mic Examples).

True Condenser Microphones

The term true condenser came about when electret microphones first became available on the market. The early electret technology was crude and low-quality. In an attempt to separate the strong condenser microphones from the weak, the term “true condenser” was coined.

True condensers require external power to activate/polarize their capacitor capsules.

Note that true condenser microphones can have either FET or vacuum tube impedance converters (electret mics are always FET).

To learn about the differences between these two types of mics, check out my article What Are The Differences Between Tube & FET Microphones?

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Related Questions

When were the moving-coil, ribbon, and condenser microphones invented? The carbon microphone was invented in 1878 by David Edward Hughes. Many years passed before the invention of our modern microphone types.

• Condenser mic was invented in 1916 by E.C Wente
• Moving-coil mic was invented in 1923 by Captain H. J. Round
• Ribbon mic was invented in 1923 by Harry F. Olsen

To learn about all the differences between condenser, dynamic, and ribbon mics, check out my article Differences Between Dynamic, Condenser, & Ribbon Microphones.

Is there such a thing as a macrophone? Technically no, there is no such thing as a macrophone. There would be no need for a device capable of capturing sounds louder than a microphone is already capable of reproducing. Dynamic mics often have theoretical maximum sound pressure levels higher than anything we'd want to record for audio playback.