Microphone Terminology: A (With Definitions)

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A-Format:

What is A-Format in ambisonics? In ambisonic recording, A-Format is the raw recording where each individual mic capsule has its own output and recording channel. For example, the first-order ambisonic tetrahedral mic outputs 4 mic signals in A-format that need to be mixed and processed into B-Format for positioning in a 3-D space.


AB Miking Technique:

What is the AB miking technique? The AB miking technique is for stereo applications and has two identical omnidirectional microphones at equal height, facing forward, and spaced 12 to 48 inches apart. At 12 inches, AB could be considered a near-coincident pair, while at 48 inches, AB is certainly a spaced pair technique.

AB Miking Technique

Absorption:

What is acoustic absorption and why is it important to microphones? Acoustic absorption is the process of a surface absorbing some or all of the energy of a colliding sound wave. As a sound wave hits a surface, part of it is reflected off of; a part is transmitted through, and another part is absorbed into the surface material. Absorptive surfaces reduce reverberation and yield “deader” acoustic spaces.


Acceptance Angle:

Also known as coverage angle or pickup angle.

What is a microphone acceptance angle? A microphone’s acceptance angle is the angle between the two points on its polar pattern where its sensitivity drops 3 dB compared to its on-axis response. Smaller angles yield more focused captures in the area the mic is pointing due to stronger off-axis rejection.

Typical acceptance angles of common polar patterns:


Acoustic Labyrinth:

What is an acoustic labyrinth and why is it used in some microphones? An acoustic labyrinth in a microphone capsule is a series of ports and pathways that act to delay sound from reaching the rear of the mic diaphragm. Capsules [most often of top-address mics] with properly designed acoustic labyrinths achieve cardioid-type polar patterns with a single diaphragm.


Acoustics:

What does acoustics mean and why is it important to microphones? Acoustics is a branch of physics about the study of mechanical waves in gases, liquids, and solids. With microphones, we’re mostly concerned with sound waves (20 Hz – 20 kHz) in air. Acoustics explains sound sources and recording spaces and helps us to understand mic design, choice, and placement.


Active Microphone:

What is an active microphone? Active mics require external power to function. Mics with internal preamps, FETs, vacuum tubes, or A/D converters are active. Condenser mics requiring external DC voltage to polarize their capsules are active. External power is provided by phantom power, DC-bias, a power supply, or a USB connection.

See: Microphone.

For a more detailed read on active microphones, check out my article Do Microphones Need Power To Function Properly?


Alternating Current (AC):

What is alternating current and how does it apply to microphones? Alternating Current (AC) is an electrical current that periodically reverses direction. Mic signals are AC, alternating between negative and positive current and voltage. A simple sine wave represents basic AC, though sound and mic signals show much more complex AC waveforms.

To visualize AC, think of how audio signals are visually represented or picture a mic or speaker diaphragm moving in one direction and then the other.

For a detailed read on microphone signals and AC voltages, check out my article What Is A Microphone Audio Signal, Electrically Speaking?


Ambient Microphone:

What is an ambient microphone? An ambient microphone is purposed with capturing ambient sounds (ie: crowd noise, distant sound and reverberation, room tone, and field ambience). Single ambient mic setups often use omnidirectional or ambisonic mics. Multiple mic setups are common for capturing stereo and surround sound ambience.

See: Microphone.

To learn about my recommended ambient microphones, check out my article Best Microphones For Recording Ambience.


Ambisonic Array:

What is an ambisonic array? An ambisonic array includes 4 or more coincident directional mic capsules pointed optimally to capture a 3-D space. This is accomplished either with multiple mics or with a single ambisonic mic. Proper mixing and processing will yield a 3-D sonic image with compatible playback formats.


Ambisonic Microphone:

What is an ambisonic microphone? An ambisonic microphone is a single mic designed to capture sound in a full-sphere surround sound format. Ambisonic mics often include 4-8 capsules (or more) in order to output sound for 3D ambisonic mixing with mi-specific software. Ambisonic mics are well suited for virtual reality recording.

See: Microphone.


Ampere (Amp):

What is an ampere and how do amperes relate to microphones? An ampere (amp) is the SI unit of electrical current (symbol: A). It is a measurement of the rate of flow of electrons (negative charge). One ampere is equal to a flow of one coulomb per second. A microphone outputs an electrical current (mic signals) to electrical represent the sound around it.


Amplification:

What is electrical amplification and how does it apply to microphones? Electrical amplification is the process of increasing the power of an electrical signal with an amplifier. Mic level signals from microphones need amplification to become line level signals for mixing consoles and DAWs. Further amplification is needed when sending these signals to loudspeakers.

For more information on microphones and amplification/amplifiers, check out the following My New Microphone articles:

Do Microphones Amplify Sound And/Or Audio?
Do Microphones Plug Into Amps? (Guitar Amps, Preamps, Power Amps, Etc).
How To Plug A Microphone Into A Guitar Or Bass Amp.


Amplitude:

What is amplitude and how does it apply to microphones? Amplitude is the maximum extent of a sound wave‘s vibration or signal’s strength from equilibrium. The amplitude of a sound wave is often measured in dB SPL or Pascals (against atmospheric pressure), whereas the amplitude of a mic signal is measured in dBV, dBu, or millivolts (against 0).


Analog:

What does analog mean and how does it apply to microphones? Analog audio refers to the electronic representation of sound. Microphones convert sound energy to electronic analog mic signals. These signals represent sound by analog AC voltages. Digital audio, by contrast, represents sound by binary digital data.

For a detailed read on analog microphones, check out my article Are Microphones Analog Or Digital Devices? (Mic Output Designs).


Analog Distortion:

What is analog distortion and how does it apply to microphones? Analog distortion in a mic is the change in its signal due to the overdriving of the electronic circuits, transistors, and tubes. Analog distortion happens as the mic is subjected to its max sound pressure level. Analog distortion is often unwanted but is used to great effect in certain situations.


Analog-Digital (A/D) Converter:

What are analog-digital converters and why are they important to microphones? Analog-digital converters (ADCs) convert analog (electrical) signals into digital information. ADCs are essential in making mic signals compatible with digital audio workstations and other digital tools. ADCs come as standalone units, in audio interfaces, and even inside of USB and digital mics.


Anechoic Chamber:

What is an anechoic chamber and what makes anechoic chambers important to microphones? An anechoic chamber is a room with surfaces that completely absorb sound and electromagnetic waves. Anechoic chambers are ideally isolated from exterior noise as well, making them 100% acoustically dead. Anechoic chambers are excellent for accurately testing mics for numerous specifications.


Angle Of Maximum Rejection:

Also known as Null Point.

What is an angle of maximum rejection in a microphone? A directional mic’s angle of maximum rejection (null point) is an angle from its axis in which it is the least sensitive to sound. Note that the directionality of mics is 3-D and so if a polar pattern has a pair of null points, it really has a “cone of rejection” rather than an “axis of rejection.”


Antenna:

What is an antenna and why are antennae important to microphones? In wireless microphone systems, an antenna is a critical interface between the mic signal itself and the radio wave propagation (carrier signal) of that mic signal through space. Antennae are essential components of wireless microphone systems in both transmitters and receivers.


Artificial Head Technique:

What is the artificial head miking technique? The artificial head miking technique utilizes a solid artificial head with a microphone placed in each ear in order to replicate a natural-sounding stereo response. The head is positioned in the ideal listening position and the mics are typically omnidirectional.


Asterisk Array:

What is a microphone asterisk array? An asterisk array is a microphone shootout method that has various mics pointing toward a single point. This is done so the engineer, producer, and/or musician can test the sound of each mic before selecting their favourite. It’s best to set the mics to have the same signal levels after preamp gain.


Attenuation:

What does attenuation mean and how does it apply to microphones? Attenuation of sound energy is the gradual decrease in a sound wave‘s power as it travels from its source. Attenuation of electrical energy (mic signals) is the reduction of signal strength in an electrical circuit. Mic placement and mic pads deal with each of these attenuation types, respectively.


Audio:

What is audio and what is the role of microphones in audio? The term audio refers to sound, especially sound that has been recorded, transmitted, or reproduced. Audio is a very broad term that can be applied to sound in the forms of electrical signals, mechanical grooves, radio transmissions, digital data, and of course, sound waves.

For a detailed read on audio, check out my article What Is The Difference Between Sound And Audio?


Audio Engineering Society (AES):

What is the Audio Engineering Society? The Audio Engineering Society (AES) is a worldwide organization for professional engineers, scientists, and others involved in the professional audio industry. The AES was founded in 1948 and is headquartered in New York City.


Audio Interface:

What is an audio interface and why are they important to microphones? An audio interface is a device that allows communication between computers and mics, instruments, loudspeakers and monitors. Audio interfaces may contain analog-digital and digital-analog converters; mic, line, and instrument inputs; USB, thunderbolt, line and other outputs; and supply phantom power.

For my recommended audio interfaces, check out my article Best Microphone Audio Interfaces.


Audio Mixer:

What is an audio mixer and why are audio mixers important to microphones? An audio mixer is a device that mixes recorded audio and/or audio inputs to make a cohesive audio output. Audio mixers can take multiple microphone signals, adjust their relative levels and panning, and add effects to create an audio mix. Mixing consoles and DAWs are the most common audio mixers.


Axis:

What is the microphone axis? The axis of a microphone is an imaginary line perpendicular to the mic diaphragm pointing away from the center of the diaphragm’s front side. On-axis sound waves propagating toward a directional mic yield the cleanest results. Top-address mics have notably different axes than side-address mics.


Axis Angle:

Also known as mutual, offset, opening or receiving angles.

What is an axis angle in reference to microphones? The axis angle is the angle between two microphone axes in a two-mic stereo miking technique. Slight variations in the axis angle can cause a sound source’s perceived position in the stereo and depth fields of stereo mixes.


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