Microphone Terminology: E (With Definitions)

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Early Reflections:

What are early reflections and how do they affect microphones? Early reflections are the first reflections a mic picks up from a sound source. Early reflections include the initial reflection and arrive at the mic less than 50 ms after the direct sound. They are not heard as echoes but as a reduction in clarity and in stereo miking, a degraded stereo imaging.


EBS Pair:

What is the EBS Pair? The EBS pair is a stereo miking technique that utilizes a pair of cardioid mics. This near-coincident pair has its mics spaced 25 cm from one another at an angle of 90°.

EBS Pair

Echo:

What is echo and how does it apply to microphones? Echo is the sound or the series of sounds caused by the reflection of a sound off a surface. Echoes should be considered when positioning mics in acoustically live spaces so that a proper balance of direct and indirect sound is picked up. Echo is also a time-based effect for mic signals in the mix.


Echo Chamber:

Also known as a reverberation chamber.

What is an echo chamber? An echo chamber is a room with highly reflective walls that is used to generate reverberation of a sound source. Echo chambers are often referred to a reverb chambers since there are no discrete echoes. There are many audio effects units that simulate echo chambers.


Edge-Terminated Capsule:

What is an edge-terminated microphone capsule? An edge-terminated mic capsule is a condenser capsule with its electrical lead terminated at the edge of the diaphragm or backplate (rather than at the centre). Though not a major factor, edge-terminated capsules, in theory, are more prone to plosives and resonance but have extended frequency response.


Electret Condenser Microphone:

What is an electret condenser microphone? An electret condenser microphone is a condenser mic that utilizes electret material to permanently polarize its parallel-plate capacitor capsule. Electret mics make up the vast majority of cell-phone, computer, headset, and lavalier mics and are also a big part of the professional microphone market.

See: Microphone.


Electrical Recording:

What is electrical audio recording? Electrical audio recording was revolutionary and established in 1925. Electrical recording allows us to effectively record and reproduce the electric AC voltages we call microphone signals. Electrical recording paved the way for tape and digital audio recording.


Electrodynamic Microphone:

What is an electrodynamic microphone? An electrodynamic mic is an antiquated type of dynamic mic that utilized an electromagnet instead of a permanent magnet. An electromagnet needs current to pass through it to create a magnetic field. As permanent magnets became more powerful and available, electrodynamic mics became obsolete.

See: Microphone.


Electromagnetic Induction:

What is electromagnetic induction and how does it apply to microphones? Electromagnetic induction is the production of a voltage across an electric conductor in a changing magnetic field. It is the working principle of dynamic mics, where the conductor (voice coil or ribbon) moves within a permanent magnetic field and, therefore, induces a voltage (the mic signal).


Electromagnetic Interference:

What is electromagnetic interference and how does it affect microphones? Electromagnetic interference (EMI) is a term for disturbances in an electrical circuit caused by external electromagnetic induction, electrostatic coupling, or conduction. EMI affects microphones, mic cables, and other audio circuits. Humbucking coils, balanced cables, and other methods help reduce EMI.


Electrostatic Principle:

What is the electrostatic principle that applies to microphones? Condenser mics work on electrostatic principles. A condenser capsule is a parallel-plate capacitor designed to hold a nearly fixed charge. The capacitance of the capsule changes as the diaphragm (movable plate) vibrates, causing an inversely proportional AC voltage (mic signal) across the plates.

The two main electrostatic equations for understanding condenser microphones are:

V=Q/C

C=kƐ0A/d

Where:

  • C is the capacitance of the capsule in farads(changes with d)
  • Q is the charge of the capsule in coulombs – (nearly constant)
  • V is the voltage across the capsule in volts(changes inversely with C)
  • k is the relative permittivity between the plates (1 for air) – (constant)
  • Ɛ0 is the permittivity of free space (8.854 x 10-12) – (constant)
  • A is the area of the two plates in meters squared – (constant)
  • d is the distance between the two plates in meters – (changes with the movement of the diaphragm)

Element:

What is a microphone element? A microphone element refers to the collective pieces that allow it to transduce energy. It is often used synonymously with the term “capsule.” Condensers, moving-coil and ribbon dynamics each have their own types of elements. Element, confusingly, can also refer to specific piece of a mic’s transducer set up.


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