Microphone Terminology: O (With Definitions)

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OCT-Hamasaki:

What is the OCT-Hamasaki miking technique? The OCT-Hamasaki is a surround sound miking technique that uses an Optimized Cardioid Triangle front array and a Hamasaki square rear/surround array. The OCT-Hamasaki uses 1 cardioid, 2 hypercardioids, and 4 bidirectional microphones and can span 4 meters deep and 3 meters wide.

OCT-Hamasaki Drawing

OCT-IRT:

What is the OCT-IRT miking technique? The OCT-IRT is a surround sound miking technique that uses an Optimized Cardioid Triangle front array (left centre and right) and an IRT Cross rear/surround array (L, LS, R, and RS). The OCT-IRT uses 5 cardioid and 2 hypercardioid mics and can span up to 133 cm deep and 100 cm wide.

OCT-IRT Cross Drawing

OCT Surround:

What is the OCT surround miking technique? OCT Surround is a surround sound miking technique with an OCT front array (L, C, and R) with two rear mics (LS and RS). The front cardioid mic (C) is 8 cm ahead of the supercardioid L and R mics. The rear cardioid mics point opposite to C and are 48 cm back and spaced 60-120 cm apart.

OCT Surround

Off-Axis:

What does off-axis mean in reference to a microphone? Any sound source that is not directly on a microphone’s primary axis (perpendicular to the centre of a diaphragm) is considered “off-axis.” There are varying degrees of off-axis sounds and a mic’s sensitivity or response to those off-axis sounds is dependent on the mic’s polar pattern.


Off-Axis Rejection:

What is off-axis rejection in a microphone? A microphone’s off-axis rejection refers to its decrease in sensitivity at a given null point. It’s how well a mic can reject sounds that aren’t where its primary pick up is. Off-axis rejection is often given as a negative dB value in the “null points” of mic’s ideal polar pattern.


Ohm:

What is an ohm and why are ohms important to microphones? The ohm is the derived SI unit that measures electrical resistant, impedance, and reactance. Mic signals are AC voltage and so they deal with impedance, which measures the apparent resistance to an AC signal in a circuit and is measured in ohms.


Olsen Stereo 180 Microphone System:

What is the Olsen stereo 180 microphone system? The Olsen stereo 180 microphone system is a near-coincident stereo miking technique aimed to provide a very wider stereo image. The Olsen 180 has two hypercardioid mics angled at 135° and spaced 2″-8″ apart. This technique provides a wide image but often suffers from the hole-in-the-middle effect.

Olsen Stereo 180 Microphone System Drawing

Olson Wing:

What is the Olson wing miking technique? The Olson wing is a baffled near-coincident stereo miking technique. It utilizes a pair of pencil mics position 4″-24″ apart in a winged baffle. Each mic sits against its own center baffle but also sits against a bottom plate. This unorthodox “wing” baffle enhances spacial definition.


Omni+8 Array:

What is the omni+8 microphone array? The omni+8 microphone array is a front array for use with surround sound miking techniques. It utilizes two omnidirectional mics (left and right) spaced 2 m apart and a bidirectional (centre) mic positioned 40 cm ahead pointing forward/backward.

Omni+8 Drawing

Omni+8 Surround:

What is the omni+8 surround miking technique? The omni+8 surround is a surround sound miking technique that uses an omni+8 frontal array with two additional omnidirectional mics (Ls and Rs) positioned 2 m apart and 4-6 m behind the front array.

Omni+8 Surround

Omnidirectional Polar Pattern:

What is an omnidirectional polar pattern? A microphone with an omnidirectional polar pattern, in theory, is equally sensitive to sound in all directions. Omnidirectional patterns are less prone to plosives, exhibit no proximity effect, and often sound more natural than their directional counterparts.

To learn more about the omnidirectional polar pattern, check out my article What Is An Omnidirectional Microphone? (Polar Pattern + Mic Examples).


On-Axis:

What does on-axis mean in reference to a microphone? On-axis means the axis or direction in which a microphone’s pick up is the most sensitive to sound. A mic is designed to pick up sound on-axis and is spec-tested with an on-axis sound. When using the term “off-axis,” we typically are talking about a sound source rather than a mic.


Operating Frequency:

What is an operating frequency in relation to a microphone? Operating frequencies are only indirectly related to microphones in that wireless mic systems transmit wireless audio within a specific radio frequency. The radio frequency sent by the transmitter and accepted by the receiver is the operating frequency of a wireless mic system.


Optimized Cardioid Triangle:

What is the optimized cardioid triangle miking technique? The optimized cardioid triangle (OCT) is a front array (left, centre, and right) technique for a surround sound array. OCT uses 3 mics in a triangle. The centre cardioid mic points ahead and is placed 3″ in front of the left/right hypercardioids that face outward 15″-40″ from each other.

Optimized Cardioid Trianlge Drawing

ORTF Pair:

What is an ORTF microphone pair? The ORTF pair is a near-coincident stereo miking technique established by the ORTF. It utilizes two cardioid mics spaced 17 cm (6.7″) apart and at an angle of 110 degrees. This popular technique yields a spacious sound while maintaining good mono compatibility.

ORTF Pair

Out-Of-Phase:

What does out-of-phase mean in relation to microphones? Out-of-phase means that the phase of two or more audio signals (mic signals) or sound waves do not align together, causing destructive interference. To be completely out-of-phase, two signals must have equal amplitude but opposite polarity (at an instant or across time).


Output Connection:

What is a microphone output connection? A microphone output connection refers to the type of connector at mic’s output. Professional mics typically have a 3-pin female XLR output connector, or a 3-pin XLR output connection.

Other output connectors of pro mics include:

To learn more about microphone output connections, check out my article What Do Microphones Plug Into? (Full List Of Mic Connections).


Output Impedance:

What is microphone output impedance? Microphone output impedance is the measure of the opposition of the mic signal at the output (in ohms). Though frequency-specific, nominal output impedance is typically the value given on a spec sheet and must be low enough to properly bridge the mic with its preamp for optimal signal transfer.


Overhead Microphone:

What is an overhead microphone? Overhead microphones are any mics positioned some distance above a sound source and point downward to capture a wide-angle of the sound source (which is often a percussion instrument). Directional overhead mic, as singles or as stereo pairs, provide a full sound of the source below them.

See: Microphone.

To learn about my recommended overhead microphones, check out articles Best Drum Overhead Microphones and Best Boom Microphones For Film.


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