A microphone, sometimes referred to as a mike or mic (both pronounced /ˈmaɪk/), is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. A transducer is a device usually electrical, electronic, Electro-mechanical, Electromagnetic, Photonic, or Photovoltaic A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies In the fields of communications, Signal processing, and in Electrical engineering more generally a signal is any time-varying or spatial-varying quantity
Microphones are used in many applications such as telephones, tape recorders, hearing aids, motion picture production, live and recorded audio engineering, in radio and television broadcasting and in computers for recording voice, VoIP, and for non-acoustic purposes such as ultrasonic checking. Georg Neumann GmbH ( Neumann) founded in 1928 and based in Berlin, Germany, is a prominent manufacturer of professional recording Microphones Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information This article deals mainly with analog tape recorders for audio applications information on digital recording, recording of video signals, and A hearing aid is an electroacoustic body-worn apparatus which typically fits in or behind the wearer's Ear, and is designed to amplify and modulate sounds Audio engineering is a part of audio science dealing with the recording and reproduction of Sound through mechanical and electronic means Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Voice-over-Internet protocol ( VoIP, vɔɪp is a protocol optimized for the transmission of voice through the Internet
History
Several early inventors built primitive microphones (then called transmitters) prior to Alexander Bell, but the first commercially practical microphone was the carbon microphone conceived in October 1876 by Thomas Edison. The carbon Microphone, also known as a carbon button microphone (or sometimes just a button microphone) or a carbon transmitter, is a sound-to-electrical Many early developments in microphone design took place at Bell Laboratories, including the first condenser microphone, described by Edward Christopher Wente of Western Electric Engineering in 1914. Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is the Research organization
Principle of operation
A microphone is a device made to capture waves in air, water (hydrophone) or hard material and translate them into an electrical signal. Edmund Dantes Lowe ( March 3, 1890 - April 21, 1971) was an American actor A hydrophone (Greek "hydro" = "water" and "phone" = "sound" is a Microphone designed to be used underwater for recording or listening The most common design uses a thin membrane which vibrates in response to sound pressure, this movement being subsequently translated into an electrical signal. Most microphones in use today for audio use electromagnetic generation (dynamic microphones), capacitance change (condenser microphones) or piezoelectric generation to produce the signal from mechanical vibration.
Microphone varieties
Condenser, capacitor or electrostatic microphones
Technology
In a condenser microphone, also known as a capacitor microphone, the diaphragm acts as one plate of a capacitor, and the vibrations produce changes in the distance between the plates. In a Loudspeaker, a diaphragm (also known as the cone) is the thin semi-rigid membrane attached to the central Magnet. A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors
There are two methods of extracting an audio output from the transducer thus formed. They are known as DC biased and RF (or HF) condenser microphones.
DC-biased microphone operating principle
The plates are biased with a fixed charge (Q). Biasing in Electronics is the method of establishing predetermined Voltages and/or Currents at various points of a circuit to set an appropriate The voltage maintained across the capacitor plates changes with the vibrations in the air, according to the capacitance equation:
where Q = charge in coulombs, C = capacitance in farads and V = potential difference in volts. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical The coulomb (symbol C) is the SI unit of Electric charge. It is named after Charles-Augustin de Coulomb. This is about the capacitance unit of measure For the charge unit see Faraday (unit. The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force. The capacitance of the plates is inversely proportional to the distance between them for a parallel-plate capacitor. (See capacitance for details. Capacitance is a measure of the amount of Electric charge stored (or separated for a given Electric potential. )
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 and the value of the bias resistor form a filter which is highpass for the audio signal, and lowpass for the bias voltage. Note that the time constant of a RC circuit equals the product of the resistance and capacitance. A resistor–capacitor circuit (RC circuit, or RC filter or RC network, is an Electric circuit composed of resistors and capacitors driven by
Within the time-frame of the capacitance change (on the order of 100 μs), the charge thus appears 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.
RF condenser microphone operating principle
In a DC-biased condenser microphone, a high capsule polarization voltage is necessary. In contrast, RF condenser microphones use a comparatively low RF voltage, generated by a low-noise oscillator. The oscillator may either be frequency 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 amplitude of the fixed-frequency oscillator signal. An LC circuit is a variety of resonant circuit or tuned circuit and consists of an Inductor, represented by the letter L and a Capacitor, represented Demodulation yields a low-noise audio frequency signal with a very low source impedance. This technique permits the use of a diaphragm with looser tension, which may be used to achieve better low-frequency response.
The RF biasing process results in a lower electrical impedance capsule, a useful byproduct of which is that RF condenser microphones can be operated in damp weather conditions which would effectively short out a DC-biased microphone. The Sennheiser "MKH" series of microphones use the RF biasing technique. Sennheiser electronic GmbH & Co KG is a private German company that makes Microphones Headphones Telephony accessories and Avionics
Usage
Condenser microphones span the range from cheap throw-aways to high-fidelity quality instruments. Patricia Lee Smith ( born December 30 1946 is an American Singer-songwriter and poet The Shure SM58 is a professional Cardioid dynamic Microphone, commonly used in live vocal applications They generally produce a high-quality audio signal and are now the popular choice in laboratory and studio recording applications. They require a power source, provided either from microphone inputs as phantom power or from a small battery. Phantom power (labeled as +48 V on some audio equipment is a method that sends a DC electrical voltage through microphone cables Power is necessary for establishing the capacitor plate voltage, and is also needed for internal amplification of the signal to a useful output level. Condenser microphones are also available with two diaphragms, the signals from which can be electrically connected such as to provide a range of polar patterns (see below), such as cardioid, omnidirectional and figure-eight. It is also possible to vary the pattern smoothly with some microphones, for example the Røde NT2000 or CAD M179. RØDE Microphones, based in Silverwater New South Wales, Australia, is a company established in 1967 by Henry and Astrid Freedman that designs and
Electret condenser microphones
An electret microphone is a relatively new type of capacitor microphone invented at Bell laboratories in 1962 by Gerhard Sessler and Jim West[1]. Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is the Research organization Gerhard M Sessler (Rosenfeld Baden-Württemberg, Germany, February 15, 1931) is a German inventor and scientist James Edward Maceo West ( February 10, 1931 &ndash is an American inventor and Acoustician. The externally-applied charge described above under condenser microphones is replaced by a fixed charge in an electret material. An electret is a ferroelectric material that has been permanently electrically charged or polarized. Electret (formed of elektr- from " Electricity " and -et from " Magnet " is a Dielectric material that has a quasi-permanent Ferroelectricity is a physical property of a material whereby it exhibits a spontaneous electric polarization, the direction of which can be switched between equivalent Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. The name comes from electrostatic and magnet; a static charge is embedded in an electret by alignment of the static charges in the material, much the way a magnet is made by aligning the magnetic domains in a piece of iron. They are used in many applications, from high-quality recording and lavalier use to built-in microphones in small sound recording devices and telephones. A lavalier microphone or lavalier (or lav or lapel mic) is a small electret or dynamic Microphone used for television theatre Though electret microphones were once low-cost and considered low quality, the best ones can now rival capacitor microphones in every respect and can even offer the long-term stability and ultra-flat response needed for a measuring microphone. Unlike other capacitor microphones, they require no polarizing voltage, but normally contain an integrated preamplifier which does require power (often incorrectly called polarizing power or bias). A preamplifier (preamp or control amp in some parts of the world is an Electronic amplifier which precedes another amplifier to prepare an electronic This preamp is frequently phantom powered in sound reinforcement and studio applications. Phantom power (labeled as +48 V on some audio equipment is a method that sends a DC electrical voltage through microphone cables While few electret microphones rival the best DC-polarized units in terms of noise level, this is not due to any inherent limitation of the electret. Rather, mass production techniques needed to produce electrets cheaply don't lend themselves to the precision needed to produce the highest quality microphones.
Dynamic microphones
Dynamic microphones work via electromagnetic induction. Faraday's law of induction describes an important basic law of electromagnetism which is involved in the working of Transformers Inductors and many forms of They are robust, relatively inexpensive and resistant to moisture, and for this reason they are widely used on-stage by singers. There are two basic types: the moving coil microphone and the ribbon microphone.
Moving coil microphones
Technology
The dynamic principle is exactly the same as in a loudspeaker, only reversed. The Shure SM57 is a common professional low Impedance Cardioid dynamic Microphone in live sound reinforcement and studio recording For the Marty Friedman album see Loudspeaker (album A loudspeaker, speaker, or speaker system is an electroacoustical A small movable induction coil, positioned in the magnetic field of a permanent magnet, is attached to the diaphragm. An induction coil or "spark coil" ( archaically known as a Ruhmkorff coil) is a type of Disruptive discharge Coil. In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges A magnet (from Greek grc μαγνήτης λίθος " Magnesian stone" is a material or object that produces a Magnetic field. In a Loudspeaker, a diaphragm (also known as the cone) is the thin semi-rigid membrane attached to the central Magnet. When sound enters through the windscreen of the microphone, the sound wave moves the diaphragm. When the diaphragm vibrates, the coil moves in the magnetic field, producing a varying current in the coil through electromagnetic induction. Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. Faraday's law of induction describes an important basic law of electromagnetism which is involved in the working of Transformers Inductors and many forms of A single dynamic membrane will not respond linearly to all audio frequencies. Some microphones for this reason utilize multiple membranes for the different parts of the audio spectrum and then combine the resulting signals. Combining the multiple signals correctly is difficult and designs that do this are rare and tend to be expensive. There are on the other hand several designs that are more specifically aimed towards isolated parts of the audio spectrum. The AKG D112, for example, is designed for bass response rather than treble. In audio engineering several kinds of microphones are often used at the same time to get the best result.
Ribbon microphones
In ribbon microphones a thin, usually corrugated metal ribbon is suspended in a magnetic field. ribbon microphone is a type of Dynamic microphone that uses a thin Aluminum, Duraluminum or nanofilm ribbon placed between the poles of a magnet to generate The ribbon is electrically connected to the microphone's output, and its vibration within the magnetic field generates the electrical signal. Ribbon microphones are similar to moving coil microphones in the sense that both produce sound by means of magnetic induction. Basic ribbon microphones detect sound in a bidirectional (also called figure-eight) pattern because the ribbon, which is open to sound both front and back, responds to the pressure gradient rather than the sound pressure. In atmospheric sciences ( Meteorology, Climatology and related fields the pressure gradient (typically of air, more generally of any Fluid) Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies Though the symmetrical front and rear pickup can be a nuisance in normal stereo recording, the high side rejection can be used to advantage by positioning a ribbon microphone horizontally, for example above cymbals, so that the rear lobe picks up only sound from the cymbals. Crossed figure 8, or Blumlein stereo recording is gaining in popularity, and the figure 8 response of a ribbon microphone is ideal for that application. Other directional patterns are produced by enclosing one side of the ribbon in an acoustic trap or baffle, allowing sound to reach only one side. Older ribbon microphones, some of which still give very high quality sound reproduction, were once valued for this reason, but a good low-frequency response could only be obtained if the ribbon is suspended very loosely, and this made them fragile. Modern ribbon materials, including new nanomaterials[2] have now been introduced that eliminate those concerns, and even improve the effective dynamic range of ribbon microphones at low frequencies. Protective wind screens can reduce the danger of damaging a vintage ribbon, and also reduce plosive artifacts in the recording. Properly designed wind screens produce negligible treble attenuation.
In common with other classes of dynamic microphone, ribbon microphones don't require phantom power; in fact, this voltage can damage some older ribbon microphones. Phantom power (labeled as +48 V on some audio equipment is a method that sends a DC electrical voltage through microphone cables (There are some new modern ribbon microphone designs which incorporate a preamplifier and therefore do require phantom power, also there are new ribbon materials available that are immune to wind blasts and phantom power. )
Carbon microphones
A carbon microphone, formerly used in telephone handsets, is a capsule containing carbon granules pressed between two metal plates. The carbon Microphone, also known as a carbon button microphone (or sometimes just a button microphone) or a carbon transmitter, is a sound-to-electrical Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 A voltage is applied across the metal plates, causing a small current to flow through the carbon. One of the plates, the diaphragm, vibrates in sympathy with incident sound waves, applying a varying pressure to the carbon. The changing pressure deforms the granules, causing the contact area between each pair of adjacent granules to change, and this causes the electrical resistance of the mass of granules to change. The changes in resistance cause a corresponding change in the voltage across the two plates, and hence in the current flowing through the microphone, producing the electrical signal. Carbon microphones were once commonly used in telephones; they have extremely low-quality sound reproduction and a very limited frequency response range, but are very robust devices.
Unlike other microphone types, the carbon microphone can also be used as a type of amplifier, using a small amount of sound energy to produce a larger amount of electrical energy. Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal. Carbon microphones found use as early telephone repeaters, making long distance phone calls possible in the era before vacuum tubes. A repeater is an electronic device that receives a signal and Retransmits it at a higher level and/or higher power or onto the other side of an obstruction These repeaters worked by mechanically coupling a magnetic telephone receiver to a carbon microphone: the faint signal from the receiver was transferred to the microphone, with a resulting stronger electrical signal to send down the line. (One illustration of this amplifier effect was the oscillation caused by feedback, resulting in an audible squeal from the old "candlestick" telephone if its earphone was placed near the carbon microphone. )
Piezoelectric microphones
Technology
A crystal microphone uses the phenomenon of piezoelectricity—the ability of some materials to produce a voltage when subjected to pressure—to convert vibrations into an electrical signal. Piezoelectricity is the ability of some materials (notably Crystals and certain Ceramics including bone to generate an Electric potential in response to An example of this is Rochelle salt (potassium sodium tartrate), which is a piezoelectric crystal that works as a transducer, both as a microphone and as a slimline loudspeaker component. Potassium sodium tartrate is a Double salt first prepared (in about 1675) by an apothecary, Pierre Seignette, of La Rochelle,
Usage
Crystal microphones used to be commonly supplied with vacuum tube (valve) equipment, such as domestic tape recorders. This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. Their high output impedance matched the high input impedance (typically about 10 megohms) of the vacuum tube input stage well. They were difficult to match to early transistor equipment, and were quickly supplanted by dynamic microphones for a time, and later small electret condenser devices. In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals The high impedance of the crystal microphone made it very susceptible to handling noise, both from the microphone itself and from the connecting cable.
Piezo transducers are often used as contact microphones to amplify sound from acoustic musical instruments, to sense drum hits for triggering electronic samples and to record sound in challenging environments, such as underwater under high pressure. A contact microphone is a form of Microphone designed not for picking up airborne sound waves but rather to act as a Transducer which picks up vibrations Saddle-mounted pickups on acoustic guitars are generally piezos that contact the strings passing over the saddle. A pickup device acts as a Transducer that captures mechanical vibrations (usually from suitably equipped Stringed instruments such as the Electric guitar See also Acoustic Guitar (magazine An acoustic guitar is a Guitar that uses only acoustic methods to project the sound produced by its strings This type of microphone is different from magnetic coil pickups commonly visible on typical electric guitars, which use magnetic induction rather than mechanical coupling to pick up vibration. A pickup device acts as a Transducer that captures mechanical vibrations (usually from suitably equipped Stringed instruments such as the Electric guitar An electric guitar is a type of Guitar that uses pickups to convert the vibration of its steel-cored strings into an electrical current which is made louder
Laser microphones
Usage
Laser microphones are very rare and expensive, and are most commonly portrayed in movies as spying devices. A laser microphone is a Surveillance device that uses a Laser beam to detect Sound Vibrations in a distant object
Liquid microphones
Technology
Early microphones did not produce intelligible speech, until Alexander Graham Bell made improvements including a variable resistance microphone/transmitter. A water microphone or water transmitter is based on Ohm's law that current in a wire varies inversely with the resistance of the circuit Bell’s liquid transmitter consisted of a metal cup filled with water with a small amount of sulfuric acid added. A sound wave caused the diaphragm to move, forcing a needle to move up and down in the water. The electrical resistance between the wire and the cup was then inversely proportional to the size of the water meniscus around the submerged needle. Elisha Gray filed a caveat for a version using a brass rod instead of the needle. A patent caveat was a Legal document filed with the United States Patent Office. Other minor variations and improvements were made to the liquid microphone by Majoranna, Chambers, Vanni, Sykes, and Elisha Gray, and one version was even patented by Reginald Fessenden in 1903.
Usage
These were the first working microphones, but they were not practical for commercial application and are utterly obsolete now. It was with a liquid microphone that the famous first phone conversation between Bell and Watson took place. Other inventors, especially Thomas Edison, soon devised superior microphones.
MEMS microphones
The MEMS (MicroElectrical-Mechanical System) microphone is also called a microphone chip or silicon microphone. Microelectromechanical systems ( MEMS) is the technology of the very small and merges at the nano-scale into Nanoelectromechanical systems (NEMS and Nanotechnology The pressure-sensitive diaphragm is etched directly into a silicon chip by MEMS techniques, and is usually accompanied with integrated preamplifier. Most MEMS microphones are variants of the condenser microphone design. Often MEMS mics have built in analog-to-digital converter (ADC) circuits on the same CMOS chip making the chip a digital microphone and so more readily integrated with modern digital products. Major manufacturers producing MEMS silicon microphones are Akustica (AKU200x), Infineon (SMM310 product), Knowles Electronics, Memstech (MSMx)and Sonion MEMS.
Speakers as microphones
A loudspeaker, a transducer that turns an electrical signal into sound waves, is the functional opposite of a microphone. For the Marty Friedman album see Loudspeaker (album A loudspeaker, speaker, or speaker system is an electroacoustical Since a conventional speaker is constructed much like a dynamic microphone (with a diaphragm, coil and magnet), speakers can actually work "in reverse" as microphones. The result, though, is a microphone with poor quality, limited frequency response (particularly at the high end), and poor sensitivity. The sensitivity of an electronic device such as a Communications system receiver or Detection device such as a PIN diode, is the minimum magnitude
In practical use, speakers are sometimes used as microphones in such applications as intercoms or walkie-talkies, where high quality and sensitivity are not needed. An intercom (intercommunication device is an electronic communications system intended for limited or private dialogue direction collaboration or announcements A walkie-talkie (more formally known as a handheld transceiver) is a hand-held portable Two-way radio Transceiver. However, there is at least one other practical application of this principle: using a medium-size woofer placed closely in front of a "kick" (bass drum) in a drum set to act as a microphone. A bass drum is a large Drum that produces a note of low definite or indefinite pitch. A drum kit (also drum set or trap set) is a collection of Drums Cymbals and sometimes other Percussion instruments such as cowbells The use of relatively large speakers to transduce low frequency sound sources, especially in music production, is becoming fairly common. Since a relatively massive membrane is unable to transduce high frequencies, placing a speaker in front of a kick drum is often ideal for reducing cymbal and snare bleed into the kick drum sound.
Less commonly, microphones themselves can be used as speakers, almost always as tweeters. A tweeter is a Loudspeaker designed to produce high frequencies typically from around 2000 Hertz to 20000 hertz (20000 Hz generally considered to be the upper This is less common since microphones are very rarely designed for handling the power speaker components are routinely required to cope with. One instance of this is the STC microphone capsule which was used as a supertweeter on the high quality B&W DM2a bookshelf loudspeaker about 1970. Standard Telephones and Cables Ltd (later STC plc) was a British Telephone, Telegraph, Radio, Telecommunications and related Bowers & Wilkins is a British Loudspeaker company that produces reference quality hi-fi and home theater speakers
Capsule design and directivity
The shape of the microphone defines its directivity. In electromagnetics, directivity is a figure of merit for an antenna. Inner elements are of major importance and concerns the structural shape of the capsule, outer elements may be the interference tube.
A pressure gradient microphone is a microphone in which both sides of the diaphragm are exposed to the incident sound and the microphone is therefore responsive to the pressure differential (gradient) between the two sides of the membrane. Sound incident parallel to the plane of the diaphragm produces no pressure differential, giving pressure-gradient microphones their characteristic figure-eight directional patterns.
The capsule of a pressure microphone however is closed on one side, which results in an omnidirectional pattern.
Microphone polar patterns
Regarding directionality, omnidirectional microphones are pressure transducers, whereas all others are pressure gradient transducers or a combination between the two.
Common polar patterns for microphones (Microphone facing top of page in diagram, parallel to page):
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A microphone's directionality or polar pattern indicates how sensitive it is to sounds arriving at different angles about its central axis. Cardioid is Closed curve with one Cusp. Definition In Geometry, the cardioid is an Epicycloid with one Cusp. The above polar patterns represent the locus of points that produce the same signal level output in the microphone if a given sound pressure level is generated from that point. In Mathematics, a locus ( Latin for "place" plural loci) is a collection of points which share a property Sound pressure is the local Pressure deviation from the ambient (average or equilibrium pressure caused by a Sound Wave. How the physical body of the microphone is oriented relative to the diagrams depends on the microphone design. For large-membrane microphones such as in the Oktava (pictured above), the upward direction in the polar diagram is usually perpendicular to the microphone body, commonly known as "side fire". For small diaphragm microphones such as the Shure (also pictured above), it usually extends from the axis of the microphone commonly known as "end fire".
Some microphone designs combine several principles in creating the desired polar pattern. This ranges from shielding (meaning diffraction/dissipation/absorption) by the housing itself to electronically combining dual membranes.
Omnidirectional
An omnidirectional microphone's response is generally considered to be a perfect sphere in three dimensions. In the real world, this is not the case. As with directional microphones, the polar pattern for an "omnidirectional" microphone is a function of frequency. The body of the microphone is not infinitely small and, as a consequence, it tends to get in its own way with respect to sounds arriving from the rear, causing a slight flattening of the polar response. This flattening increases as the diameter of the microphone (assuming it's cylindrical) reaches the wavelength of the frequency in question. Therefore, the smallest diameter microphone will give the best omnidirectional characteristics at high frequencies. The wavelength of sound at 10 kHz is little over an inch (3. 4 cm) so the smallest measuring microphones are often 1/4" (6 mm) in diameter, which practically eliminates directionality even up to the highest frequencies. Omnidirectional microphones, unlike cardioids, do not employ resonant cavities as delays, and so can be considered the "purest" microphones in terms of low coloration; they add very little to the original sound. Being pressure-sensitive they can also have a very flat low-frequency response down to 20 Hz or below. Pressure-sensitive microphones also respond much less to wind noise than directional (velocity sensitive) microphones.
Unidirectional
A unidirectional microphone is sensitive to sounds from only one direction. The diagram above illustrates a number of these patterns. The microphone faces upwards in each diagram. The sound intensity for a particular frequency is plotted for angles radially from 0 to 360°. (Professional diagrams show these scales and include multiple plots at different frequencies. The diagrams given here provide only an overview of typical pattern shapes, and their names. )
Cardioids
The most common unidirectional microphone is a cardioid microphone, so named because the sensitivity pattern is heart-shaped (see cardioid). Cardioid is Closed curve with one Cusp. Definition In Geometry, the cardioid is an Epicycloid with one Cusp. A hyper-cardioid is similar but with a tighter area of front sensitivity and a tiny lobe of rear sensitivity. A super-cardioid microphone is similar to a hyper-cardioid, except there is more front pickup and less rear pickup. These three patterns are commonly used as vocal or speech microphones, since they are good at rejecting sounds from other directions.
Bi-directional
Figure 8 or bi-directional microphones receive sound from both the front and back of the element. Most ribbon microphones are of this pattern.
Shotgun
Shotgun microphones are the most highly directional. They have small lobes of sensitivity to the left, right, and rear but are significantly more sensitive to the front. This results from placing the element inside a tube with slots cut along the side; wave-cancellation eliminates most of the off-axis noise. Shotgun microphones are commonly used on TV and film sets, and for field recording of wildlife.
An omnidirectional microphone is a pressure transducer; the output voltage is proportional to the air pressure at a given time.
On the other hand, a figure-8 pattern is a pressure gradient transducer; A sound wave arriving from the back will lead to a signal with a polarity opposite to that of an identical sound wave from the front. Moreover, shorter wavelengths (higher frequencies) are picked up more effectively than lower frequencies.
A cardioid microphone is effectively a superposition of an omnidirectional and a figure-8 microphone; for sound waves coming from the back, the negative signal from the figure-8 cancels the positive signal from the omnidirectional element, whereas for sound waves coming from the front, the two add to each other. A hypercardioid microphone is similar, but with a slightly larger figure-8 contribution.
Since pressure gradient transducer microphones are directional, putting them very close to the sound source (at distances of a few centimeters) results in a bass boost. A transducer is a device usually electrical, electronic, Electro-mechanical, Electromagnetic, Photonic, or Photovoltaic This is known as the proximity effect[3]
Application-specific microphone designs
A lavalier microphone is made for hands-free operation. The proximity effect in audio refers to a change in the Frequency response of a Directional microphone as the sound source is brought close to the Microphone A lavalier microphone or lavalier (or lav or lapel mic) is a small electret or dynamic Microphone used for television theatre These small microphones are worn on the body and held in place either with a lanyard worn around the neck or a clip fastened to clothing. The cord may be hidden by clothes and either run to an RF transmitter in a pocket or clipped to a belt (for mobile use), or run directly to the mixer (for stationary applications).
A wireless microphone is one which does not use a cable. A wireless microphone, as the name implies is a Microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated It usually transmits its signal using a small FM radio transmitter to a nearby receiver connected to the sound system, but it can also use infrared light if the transmitter and receiver are within sight of each other.
A contact microphone is designed to pick up vibrations directly from a solid surface or object, as opposed to sound vibrations carried through air. A contact microphone is a form of Microphone designed not for picking up airborne sound waves but rather to act as a Transducer which picks up vibrations One use for this is to detect sounds of a very low level, such as those from small objects or insects. Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described The microphone commonly consists of a magnetic (moving coil) transducer, contact plate and contact pin. The contact plate is placed against the object from which vibrations are to be picked up; the contact pin transfers these vibrations to the coil of the transducer. Contact microphones have been used to pick up the sound of a snail's heartbeat and the footsteps of ants. A portable version of this microphone has recently been developed.
A throat microphone is a variant of the contact microphone, used to pick up speech directly from the throat, around which it is strapped. A throat microphone, also laryngophone is a type of Microphone that picks up sound directly through sensors in contact with the neck This allows the device to be used in areas with ambient sounds that would otherwise make the speaker inaudible.
A parabolic microphone uses a parabolic reflector to collect and focus sound waves onto a microphone receiver, in much the same way that a parabolic antenna (e. A parabolic microphone is a Microphone that uses a Parabolic reflector to collect and focus Sound waves onto a receiver in much the same way that a A parabolic reflector (or dish or mirror) is a Parabola -shaped reflective device used to collect or distribute Energy such as The parabolic antenna is a high-gain reflector antenna used for radio television and data communications and also for radiolocation ( RADAR) on the UHF and g. satellite dish) does with radio waves. A satellite dish is a type of Parabolic antenna that receives or transmits electromagnetic signals to and from another location typically a satellite Typical uses of this microphone, which has unusually focused front sensitivity and can pick up sounds from many meters away, include nature recording, outdoor sporting events, eavesdropping, law enforcement, and even espionage. Eavesdropping is the act of surreptitiously listening to a private conversation Parabolic microphones are not typically used for standard recording applications, because they tend to have poor low-frequency response as a side effect of their design.
A stereo microphone integrates two microphones in one unit to produce a stereophonic signal. A stereo microphone is often used for broadcast applications or field recording where it would be impractical to configure two separate condenser microphones in a classic X-Y configuration (see microphone practice) for stereophonic recording. For the band see Broadcast (band Broadcasting is the distribution of audio and/or Video signals which transmit Field recording is the technique for capturing the audible illustration of an environment produced outside of a Recording studio. See also Microphone There exist a number of well-developed Microphone techniques used for miking musical film or voice sources Some such microphones have an adjustable angle of coverage between the two channels.
A noise-canceling microphone is intended for noisy environments such as aircraft cockpits. They are normally installed as boom mics on headsets. They pick up environmental noise, ideally without also picking up the intended signal, with one diaphragm and electrically combine the output with the intended signal picked up with another diaphragm. In older designs, there is no active electronics involved in the cancellation technique, unlike active noise cancellation microphones. So, in the common configuration, the intended signal is voice and one diaphragm is mounted close to the mouth. The other is, often, placed behind the first, farther away from the intended signal source and electrically out of phase with the first. After combination, signals other than the voice are greatly reduced, substantially increasing intelligibility. Some noise-canceling microphones are also throat microphones.
Connectivity
Connectors
The most common connectors used by microphones are:
- Male XLR connector on professional microphones
- ¼ inch mono phone plug on less expensive consumer microphones
- 3. The XLR connector is an Electrical connector design XLR Plugs and sockets are used mostly in professional audio and Video A TRS connector, also called an audio jack, phone plug, jack plug, stereo plug, mini-jack, or mini-stereo, is a common 5 mm (Commonly referred to as 1/8 inch mini) stereo (wired as mono) mini phone plug on very inexpensive and computer microphones
Some microphones use other connectors, such as 1/4 inch TRS (tip ring sleeve), 5-pin XLR, or stereo mini phone plug (1/8 inch TRS) on some stereo microphones. A TRS connector, also called an audio jack, phone plug, jack plug, stereo plug, mini-jack, or mini-stereo, is a common Some lavalier microphones use a proprietary connector for connection to a wireless transmitter. Since 2005, professional-quality microphones with USB connections have begun to appear, designed for direct recording into computer-based software.
Impedance matching
Microphones have an electrical characteristic called impedance, measured in ohms (Ω), that depends on the design. Any linear electronic circuit or device which supplies a current may be modelled as an Ideal voltage source in series with an impedance. The ohm (symbol Ω) is the SI unit of Electrical impedance or in the Direct current case Electrical resistance, Typically, the rated impedance is stated. [4] Low impedance is considered under 600 Ω. Medium impedance is considered between 600 Ω and 10 kΩ. High impedance is above 10 kΩ.
Most professional microphones are low impedance, about 200 Ω or lower. Low-impedance microphones are preferred over high impedance for two reasons: one is that using a high-impedance microphone with a long cable will result in loss of high frequency signal due to the capacitance of the cable; the other is that long high-impedance cables tend to pick up more hum (and possibly radio-frequency interference (RFI) as well). Electric hum, Mains hum, or power line hum is an audible oscillation at the frequency of the Mains Alternating current However, some devices, such as vacuum tube guitar amplifiers, have an input impedance that is inherently high, requiring the use of a high impedance microphone or a matching transformer. Nothing will be damaged if the impedance between microphone and other equipment is mismatched; the worst that will happen is a reduction in signal or change in frequency response.
To get the best sound in most cases, the impedance of the microphone must be distinctly lower (by a factor of at least five) than that of the equipment to which it is connected. Most microphones are designed not to have their impedance "matched" by the load to which they are connected; doing so can alter their frequency response and cause distortion, especially at high sound pressure levels. There are transformers (confusingly called matching transformers) that adapt impedances for special cases such as connecting microphones to DI units or connecting low-impedance microphones to the high-impedance inputs of certain amplifiers, but microphone connections generally follow the principle of bridging (voltage transfer), not matching (power transfer). A DI unit, DI box, Direct Box or simply DI is an electronic device that connects a high impedance Line level signal that has an unbalanced In general, any XLR microphone can usually be connected to any mixer with XLR microphone inputs, and any plug microphone can usually be connected to any jack that is marked as a microphone input, but not to a line input. This is because the signal level of a microphone is typically 40 to 60 dB lower (a factor of 100 to 1000) than a line input. Microphone inputs include the necessary amplification to handle these very low level signals. Certain ribbon and dynamic microphones, which are most linear when operated into a load of known impedance, are exceptions. [5]
Digital microphone interface
The AES 42 standard, published by the Audio Engineering Society, defines a digital interface for microphones. Established in 1948 the Audio Engineering Society (AES draws its membership from amongst engineers scientists manufacturers and other organizations and individuals with an interest Microphones conforming to this standard directly output a digital audio stream through an XLR male connector, rather than producing an analog output. Digital microphones may be used either with new equipment which has the appropriate input connections conforming to the AES 42 standard, or else by use of a suitable interface box. Studio-quality microphones which operate in accordance with the AES 42 standard are now appearing from a number of microphone manufacturers.
Measurements and specifications
Because of differences in their construction, microphones have their own characteristic responses to sound. The Shure SM58 is a professional Cardioid dynamic Microphone, commonly used in live vocal applications This difference in response produces non-uniform phase and frequency responses. The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0 Frequency is a measure of the number of occurrences of a repeating event per unit Time. In addition, microphones are not uniformly sensitive to sound pressure, and can accept differing levels without distorting. Although for scientific applications microphones with a more uniform response are desirable, this is often not the case for music recording, as the non-uniform response of a microphone can produce a desirable coloration of the sound. There is an international standard for microphone specifications,[6] but few manufacturers adhere to it. As a result, comparison of published data from different manufacturers is difficult because different measurement techniques are used. The Microphone Data Website has collated the technical specifications complete with pictures, response curves and technical data from the microphone manufacturers for every currently listed microphone, and even a few obsolete models, and shows the data for them all in one common format for ease of comparison. [1]. Caution should be used in drawing any solid conclusions from this or any other published data, however, unless it is known that the manufacturer has supplied specifications in accordance with IEC 60268-4.
A frequency response diagram plots the microphone sensitivity in decibels over a range of frequencies (typically at least 0–20 kHz), generally for perfectly on-axis sound (sound arriving at 0° to the capsule). The decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to Frequency response may be less informatively stated textually like so: "30 Hz–16 kHz ±3 dB". This is interpreted as a (mostly) linear plot between the stated frequencies, with variations in amplitude of no more than plus or minus 3 dB. However, one cannot determine from this information how smooth the variations are, nor in what parts of the spectrum they occur. Note that commonly-made statements such as "20 Hz–20 kHz" are meaningless without a decibel measure of tolerance. Directional microphones' frequency response varies greatly with distance from the sound source, and with the geometry of the sound source. IEC 60268-4 specifies that frequency response should be measured in plane progressive wave conditions (very far away from the source) but this is seldom practical. Close talking microphones may be measured with different sound sources and distances, but there is no standard and therefore no way to compare data from different models unless the measurement technique is described.
The self-noise or equivalent noise level is the sound level that creates the same output voltage as the microphone does in the absence of sound. This represents the lowest point of the microphone's dynamic range, and is particularly important should you wish to record sounds that are quiet. The measure is often stated in dB(A), which is the equivalent loudness of the noise on a decibel scale frequency-weighted for how the ear hears, for example: "15 dBA SPL" (SPL means sound pressure level relative to 20 micropascals). The lower the number the better. Some microphone manufacturers state the noise level using ITU-R 468 noise weighting, which more accurately represents the way we hear noise, but gives a figure some 11 to 14 dB higher. The ITU-R 468-weighting curve (originally defined in CCIR recommendation 468 is widely used when measuring noise in audio systems especially in the UK Europe and former countries of A quiet microphone will measure typically 20 dBA SPL or 32 dB SPL 468-weighted. Very quiet microphones have existed for years for special applications, such the Brüel & Kjaer 4179, with a noise level around 0 dB SPL. Recently some microphones with low noise specifications have been introduced in the studio/entertainment market, such as models from Neumann and Røde that advertise noise levels between 5 and 7 dBA. Neumann ( German for "new man" and one of the 20 most common German surnames may refer to Alfred Neumann, German playwright RØDE Microphones, based in Silverwater New South Wales, Australia, is a company established in 1967 by Henry and Astrid Freedman that designs and Typically this is achieved by altering the frequency response of the capsule and electronics to result in lower noise within the A-weighting curve while broadband noise may be increased.
The maximum SPL (sound pressure level) the microphone can accept is measured for particular values of total harmonic distortion (THD), typically 0. Sound pressure is the local Pressure deviation from the ambient (average or equilibrium pressure caused by a Sound Wave. The total harmonic distortion, or THD, of a signal is a measurement of the Harmonic distortion present and is defined as the ratio of the sum of the powers 5%. This is generally inaudible, so one can safely use the microphone at this level without harming the recording. Example: "142 dB SPL peak (at 0. Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies 5% THD)". The higher the value, the better, although microphones with a very high maximum SPL also have a higher self-noise.
The clipping level is perhaps a better indicator of maximum usable level, as the 1% THD figure usually quoted under max SPL is really a very mild level of distortion, quite inaudible especially on brief high peaks. Harmonic distortion from microphones is usually of low-order (mostly third harmonic) type, and hence not very audible even at 3-5%. Clipping, on the other hand, usually caused by the diaphragm reaching its absolute displacement limit (or by the preamplifier), will produce a very harsh sound on peaks, and should be avoided if at all possible. For some microphones the clipping level may be much higher than the max SPL.
The dynamic range of a microphone is the difference in SPL between the noise floor and the maximum SPL. If stated on its own, for example "120 dB", it conveys significantly less information than having the self-noise and maximum SPL figures individually.
Sensitivity indicates how well the microphone converts acoustic pressure to output voltage. The sensitivity of an electronic device such as a Communications system receiver or Detection device such as a PIN diode, is the minimum magnitude A high sensitivity microphone creates more voltage and so will need less amplification at the mixer or recording device. This is a practical concern but is not directly an indication of the mic's quality, and in fact the term sensitivity is something of a misnomer, 'transduction gain' being perhaps more meaningful, (or just "output level") because true sensitivity will generally be set by the noise floor, and too much "sensitivity" in terms of output level will compromise the clipping level. There are two common measures. The (preferred) international standard is made in millivolts per pascal at 1 kHz. A higher value indicates greater sensitivity. The older American method is referred to a 1 V/Pa standard and measured in plain decibels, resulting in a negative value. Again, a higher value indicates greater sensitivity, so −60 dB is more sensitive than −70 dB.
Measurement microphones
Some microphones are intended for use as standard measuring microphones for the testing of speakers and checking noise levels etc. These are calibrated transducers and will usually be supplied with a calibration certificate stating absolute sensitivity against frequency.
Microphone calibration techniques
Measurement microphones are used in sound analysis meters, noise measurement (in public nuisance abatement contexts), acoustic laboratories, loudspeaker design and quality control work, etc. They are made with greater care than most microphones and generally come with a calibration certificate. However, like most manufactured products there can be variations, which may change over the lifetime of the device. Accordingly, it is regularly necessary to test the test microphones. This service is offered by some microphone manufacturers and by independent certified testing labs. Some test enough microphones to justify an in-house calibration lab. Depending on the application, measurement microphones must be tested periodically (every year or several months, typically) and after any potentially damaging event, such as being dropped (most such mikes come in foam-padded cases to reduce this risk) or exposed to sounds beyond the acceptable level.
Pistonphone apparatus
A pistonphone is an acoustical calibrator (sound source) using a closed coupler to generate a precise sound pressure for the calibration of instrumentation microphones. The principle relies on a piston mechanically driven to move at a specified rate on a fixed volume of air to which the microphone under test is exposed. The air is assumed to be compressed adiabatically and the SPL in the chamber can be calculated from the adiabatic gas law, which requires that the product of the pressure P with V raised to the power gamma be constant; here gamma is the ratio of the specific heat of air at constant pressure to its specific heat at constant volume. The pistonphone method only works at low frequencies, but it can be accurate and yields an easily calculable sound pressure level. The standard test frequency is usually around 250 Hz.
Reciprocal method
This method relies on the reciprocity of one or more microphones in a group of 3 to be calibrated. It can still be used when only one of the microphones is reciprocal (exhibits equal response when used as a microphone or as a loudspeaker).
Microphone array and array microphones
A microphone array is any number of microphones operating in tandem. A microphone array is any number of Microphones operating in Tandem. Tandem is a Latin Adverb meaning "at length" or "finally" There are many applications:
- Systems for extracting voice input from ambient noise (notably telephones, speech recognition systems, hearing aids)
- Surround sound and related technologies
- Locating objects by sound: acoustic source localization, e. In atmospheric sound transmission or Noise pollution, ambient noise level is the sound pressure level at a given location normally specified as a reference level to study a Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information Speech recognition (also known as automatic speech recognition or computer speech recognition) converts spoken words to machine-readable input (for example to keypresses A hearing aid is an electroacoustic body-worn apparatus which typically fits in or behind the wearer's Ear, and is designed to amplify and modulate sounds 51, Multichannel audio, Multichannel music Surround 3D Surround 5 Acoustic source localization is the task of locating a Sound source given measurements of the sound field at several disparate locations g. military use to locate the source(s) of artillery fire. Aircraft location and tracking.
- High fidelity original recordings
Typically, an array is made up of omnidirectional microphones distributed about the perimeter of a space, linked to a computer that records and interprets the results into a coherent form. High fidelity or hi-fi reproduction is a term used by home stereo listeners and home audio enthusiasts ( Audiophiles to refer to high-quality reproduction The perimeter is the distance around a given two-dimensional object A computer is a Machine that manipulates data according to a list of instructions.
Microphone windscreens
Windscreens are used to protect microphones that would otherwise be buffeted by wind or vocal plosives (from consonants such as "P", "B", etc. A stop, plosive, or occlusive is a Consonant sound produced by stopping the airflow in the Vocal tract. ). Most microphones have an integral windscreen built around the microphone diaphragm. A screen of plastic, wire mesh or a metal cage is held at a distance from the microphone diaphragm, to shield it. This cage provides a first line of defense against the mechanical impact of objects or wind. Some microphones, such as the Shure SM58, may have an additional layer of foam inside the cage to further enhance the protective properties of the shield. Shure Incorporated is a consumer and professional audio electronics Corporation. The Shure SM58 is a professional Cardioid dynamic Microphone, commonly used in live vocal applications Beyond integral microphone windscreens, there are three broad classes of additional wind protection.
Microphone covers
Microphone covers are often made of soft open-cell polyester or polyurethane foam because of the inexpensive, disposable nature of the foam. Optional windscreens are often available from the manufacturer and third parties. A very visible example of optional accessory windscreen is the A2WS from Shure, one of which is fitted over each of the two SM57s used on the United States Presidential lectern. The Shure SM57 is a common professional low Impedance Cardioid dynamic Microphone in live sound reinforcement and studio recording [7]. One disadvantage of polyurethane foam microphone covers is that they can deteriorate over time. Windscreens also tend to collect dirt and moisture in their open cells and must be cleaned to prevent high frequency loss, bad odor and unhealthy conditions for the person using the microphone. On the other hand, a major advantage of concert vocalist windscreens is that one can quickly change to a clean windscreen between users, reducing the chance of transferring germs. Windscreens of various colors can be used to distinguish one microphone from another on a busy, active stage.
Pop filters
Pop filters or pop screens are used in controlled studio environments to keep plosives down when recording. A pop filter or pop shield is an anti-pop Noise protection filter for microphones, typically used in a Recording studio. A typical pop filter is composed of one or more layers of acoustically semi-transparent material such as woven nylon stretched over a circular frame and a clamp and a flexible mounting bracket to attach to the microphone stand. A pop filter or pop shield is an anti-pop Noise protection filter for microphones, typically used in a Recording studio. The pop shield is placed between the vocalist and the microphone. The need for a windscreen increases the closer a vocalist brings the microphone to their lips. Singers can be trained to soften their plosives, in which case they don't need a windscreen for any reason other than wind.
Blimps
Blimps (also known as zeppelins) are large hollow windscreens used to surround microphones for outdoor location audio, such as nature recording, electronic news gathering, and for film and video shoots. ENG is a Broadcasting (usually Television) industry acronym which stands for electronic news gathering. They can cut wind noise by as much as 25 dB, especially low-frequency noise. The blimp is essentially a hollow cage or basket with acoustically transparent material stretched over the outer frame. The blimp works by creating a volume of still air around the microphone. The microphone is often further isolated from the blimp by an elastic suspension inside the basket. This reduces wind vibrations and handling noise transmitted from the cage. To extend the range of wind speed conditions in which the blimp will remain effective, many have the option of fitting a secondary cover over the outer shell. This is usually a furry material with long soft hairs and a weave that is as acoustically transparent as possible. The hair acts as a filter to any wind turbulence hitting the blimp. A synthetic furry cover can reduce wind noise by a further 12 dB. [8].
One disadvantage of all windscreen types is that the microphone's high frequency response is attenuated by a small amount depending on the density of the protective layer.
See also
- Loudspeaker (the inverse of a microphone)
- Hydrophone (microphone for underwater use)
- Geophone (microphone for use within the earth)
- Ionophone (plasma-based microphone)
- Microphone connector
- Microphone practice
- A-weighting
- Button microphone
- ITU-R 468 noise weighting
- Nominal impedance — Information about impedance matching for audio components
- Sound pressure level
- Wireless microphone
- XLR connector — The 3-pin variant of which is used for connecting microphones
References
- ^ "Electret Microphone Turns 40"
- ^ "Local firms strum the chords of real music innovation" (February 8, 2008). For the Marty Friedman album see Loudspeaker (album A loudspeaker, speaker, or speaker system is an electroacoustical A hydrophone (Greek "hydro" = "water" and "phone" = "sound" is a Microphone designed to be used underwater for recording or listening The term geophone derives from the Greek word "geo" meaning " earth " and "phone" meaning "sound" An ionophone is a transducer for converting acoustic vibrations in plasma into an electrical signal or for converting an electrical signal into acoustic vibrations in plasma It can be used Many different electrical connectors have been used to connect microphones to audio equipment---including PA systems radios tape recorders and numerous other devices See also Microphone There exist a number of well-developed Microphone techniques used for miking musical film or voice sources A-weighting is the most commonly used of a family of curves defined in the International standard IEC616722003 and various national standards relating to the measurement of sound The carbon Microphone, also known as a carbon button microphone (or sometimes just a button microphone) or a carbon transmitter, is a sound-to-electrical The ITU-R 468-weighting curve (originally defined in CCIR recommendation 468 is widely used when measuring noise in audio systems especially in the UK Europe and former countries of The term nominal impedance in Electrical engineering or audio has a number of different meanings Impedance matching is the electronics design practice of setting the Output impedance ( Z S of a signal source equal to the Input impedance ( Sound pressure is the local Pressure deviation from the ambient (average or equilibrium pressure caused by a Sound Wave. A wireless microphone, as the name implies is a Microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated The XLR connector is an Electrical connector design XLR Plugs and sockets are used mostly in professional audio and Video Events 421 - Constantius III becomes co- Emperor of the Western Roman Empire. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Mass High Tech: The Journal of New England Technology.
- ^ http://www.tonmeister.ca/main/textbook/node473.html Introduction To Sound Recording Geoff Martin
- ^ International Standard IEC 60268-4
- ^ Robertson, A. E. : "Microphones" Illiffe Press for BBC, 1951-1963
- ^ International Standard IEC 60268-4
- ^ Shure - Accessories - A2WS Microphone Windscreens
- ^ http://www.rycote.com/products/windshield/
External links
- Info, Pictures and Soundbytes from vintage microphones
- Microphone construction and basic placement advice
- History of the Microphone
- Microphone sensitivity conversion — dB re 1 V/Pa and transfer factor mV/Pa
- Large vs. Small Diaphragms in Omnidirectional Microphones
- Microphone Expressions Lexicon
- WikiMusician's article on Stereo Microphone, including sound demos
- WikiRecording's Guide to Condenser Microphones
- How to Mic a Bass Speaker Cabinet, including diagrams and sound files from WikiMusician.org
Dictionary
microphone
-noun
- A device (transducer) used to convert sound waves into a varying electric current; normally fed into an amplifier and either recorded or broadcast.
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