Editing Microphone (section)

=== Condenser <span class="anchor" id="Condenser microphone"></span>===
<!--"Condenser microphone", "Consensor microphone", "Condenser mic" redirect here.-->
[[File:Oktava319-internal.jpg|thumb|upright|Inside the Oktava 319 condenser microphone]]
[[File:Condenser microphone.svg|thumb|Inner workings of the condenser microphone]]

The '''condenser microphone''', invented at Western Electric in 1916 by E. C. Wente,<ref>{{cite web |url=http://www.stokowski.org/Development_of_Electrical_Recording.htm |title=Bell Laboratories and The Development of Electrical Recording |website=Stokowski.org (Leopold Stokowski site) |archive-url=https://web.archive.org/web/20230621223522/http://www.stokowski.org/Development_of_Electrical_Recording.htm |archive-date=June 21, 2023 }}</ref> is also called a '''capacitor microphone''' or '''electrostatic microphone'''—capacitors were historically called condensers. The diaphragm acts as one plate of a capacitor, and audio vibrations produce changes in the distance between the plates. Because the capacitance of the plates is inversely proportional to the distance between them, the vibrations produce changes in capacitance. These changes in capacitance are used to measure the [[audio signal]].<ref>{{cite encyclopedia |title=Electromechanical Transducer |url=https://www.britannica.com/technology/electromechanical-transducer |encyclopedia=Britannica |access-date=June 2, 2024 }}</ref> The assembly of fixed and movable plates is called an ''element'' or ''capsule''.

Condenser microphones span the range from telephone mouthpieces through inexpensive karaoke microphones to high-fidelity recording microphones. They generally produce a high-quality audio signal and are now the popular choice in laboratory and [[recording studio]] applications. The inherent suitability of this technology is due to the very small mass that must be moved by the incident sound wave compared to other microphone types that require the sound wave to do more work.

Condenser microphones require a power source, provided either via microphone inputs on equipment as [[phantom power]] or from a small battery. Power is necessary for establishing the capacitor plate voltage and is also needed to power the microphone electronics. Condenser microphones are also available with two diaphragms that can be electrically connected to provide a range of [[#Microphone polar patterns|polar patterns]], such as cardioid, omnidirectional, and figure-eight. It is also possible to vary the pattern continuously with some microphones, for example, the [[Røde]] NT2000 or CAD M179.

There are two main categories of condenser microphones, depending on the method of extracting the audio signal from the transducer: DC-biased microphones, and radio frequency (RF) or high frequency (HF) condenser microphones.

==== DC-biased condenser ====
With a '''DC-biased condenser microphone''', the plates are [[Voltage bias|biased]] with a fixed charge (''Q''). The [[voltage]] maintained across the capacitor plates changes with the vibrations in the air, according to the capacitance equation (C = {{fract|Q|V}}), where Q = charge in [[coulomb]]s, C = capacitance in [[farad]]s and V = potential difference in [[volt]]s. A nearly constant charge is maintained on the capacitor. As the capacitance changes, the charge across the capacitor does change very slightly, but at audible frequencies it is sensibly constant. The capacitance of the capsule (around 5 to 100&nbsp;[[Farad|pF]]) and the value of the bias resistor (100&nbsp;[[Ohm|MΩ]] to tens of GΩ) form a filter that is high-pass for the audio signal, and low-pass for the bias voltage. Note that the time constant of an [[RC circuit]] equals the product of the resistance and capacitance.

Within the time frame of the capacitance change (as much as 50&nbsp;ms at 20&nbsp;Hz audio signal), the charge is practically constant and the voltage across the capacitor changes instantaneously to reflect the change in capacitance. The voltage across the capacitor varies above and below the bias voltage. The voltage difference between the bias and the capacitor is seen across the series resistor. The voltage across the resistor is amplified for performance or recording. In most cases, the electronics in the microphone itself contribute no voltage gain as the voltage differential is quite significant, up to several volts for high sound levels.

==== RF condenser ====
[[File:AKG C451B.jpg|thumb|[[AKG Acoustics|AKG]] C451B small-diaphragm condenser microphone]]

'''RF condenser microphones''' use a comparatively low RF voltage, generated by a low-noise oscillator. The signal from the oscillator may either be amplitude modulated by the capacitance changes produced by the sound waves moving the capsule diaphragm, or the capsule may be part of a [[resonant circuit]] that modulates the frequency of the oscillator signal. Demodulation yields a low-noise audio frequency signal with a very low source impedance. The absence of a high bias voltage permits the use of a diaphragm with looser tension, which may be used to achieve wider frequency response due to higher compliance. The RF biasing process results in a lower electrical impedance capsule, a useful by-product of which is that RF condenser microphones can be operated in damp weather conditions that could create problems in DC-biased microphones with contaminated insulating surfaces. The [[Sennheiser]] MKH series of microphones use the RF biasing technique. A covert, remotely energized application of the same physical principle called [[The Thing (listening device)|the Thing]] was devised by Soviet Russian inventor [[Leon Theremin]] and used to bug the US Ambassador's residence in Moscow between 1945 and 1952.

==== Electret condenser ====
{{Main|Electret microphone}}
[[File:US Patent 3118022 - Gerhard M. Sessler James E. West - Bell labs - electroacustic transducer - foil electret condenser microphone 1962 1964 - pages 1-3.png|thumb|left|First patent on foil electret microphone by G. M. Sessler et al. (pages 1 to 3)]]

An electret microphone is a type of condenser microphone invented by [[Gerhard Sessler]] and [[James Edward Maceo West|Jim West]] at [[Bell laboratories]] in 1962.<ref>{{cite journal |first1=G.M. |last1=Sessler |last2=West |first2=J.E. |title=Self-Biased Condenser Microphone with High Capacitance |journal=Journal of the Acoustical Society of America |volume=34 |date=1962 |pages=1787–1788 |doi=10.1121/1.1909130 |issue=11 |bibcode=1962ASAJ...34.1787S }}</ref> The externally applied charge used for a conventional condenser microphone is replaced by a permanent charge in an electret material. An [[electret]] is a [[ferroelectric]] material that has been permanently [[Electric charge|electrically charged]] or ''polarized''. The name comes from ''electrostatic'' and ''magnet''; a static charge is embedded in an electret by the alignment of the static charges in the material, much the way a [[permanent magnet]] is made by aligning the magnetic domains in a piece of iron.

Due to their good performance and ease of manufacture, hence low cost, the vast majority of microphones made today are electret microphones; a semiconductor manufacturer estimates annual production at over one billion units.<ref>{{cite web |last=Van Rhijn |first=Arie |url=http://www.national.com/nationaledge/dec02/article.html |title=Integrated Circuits for High Performance Electret Microphones |publisher=National Semiconductor |archive-url=https://web.archive.org/web/20100819045334/http://www.national.com/nationaledge/dec02/article.html |archive-date=August 19, 2010 }}</ref> They are used in many applications, from high-quality recording and [[Lavalier microphone|lavalier]] (lapel mic) use to built-in microphones in small sound recording devices and telephones. Prior to the proliferation of MEMS microphones, nearly all cell-phone, computer, PDA and headset microphones were electret types.{{Citation needed|date=December 2023}}

Unlike other capacitor microphones, they require no polarizing voltage, but often contain an integrated [[Microphone preamplifier|preamplifier]] that does require power. This preamplifier is frequently phantom powered in [[sound reinforcement]] and studio applications. Monophonic microphones designed for [[personal computer]]s (PCs), sometimes called multimedia microphones, use a 3.5&nbsp;mm plug as usually used for stereo connections; the ring, instead of carrying the signal for a second channel, carries power.

==== Valve microphone ====
{{Main|Valve microphone}}

A valve microphone is a condenser microphone that uses a [[vacuum tube]] (valve) [[Valve amplifier|amplifier]].<ref>{{cite web |last=Institute BV Amsterdam |first=SAE |title=Microphones |url=http://www.sae.edu/reference_material/audio/pages/Microphones.htm |publisher=Practical Creative Media Education |access-date=March 7, 2014 }}</ref> They remain popular with enthusiasts of [[tube sound]].