Balanced - A circuit that carries information by means of two equal but opposite polarity signals, on two conductors.
Bidirectional Microphone - A microphone that picks up equally from two opposite directions. The angle of best rejection is 90 degrees from the front (or rear) of the microphone, that is, directly at the sides.
Boundary/Surface Microphone - A microphone designed to be mounted on an acoustically reflective surface.

-C-
Cardioid Microphone - A unidirectional microphone with moderately wide front pickup (131 degrees). Angle of best rejection is 180 degrees from the front of the microphone, that is, directly at the rear.
Cartridge (Transducer) - The element in a microphone that converts acoustical energy (sound) into electrical energy (the signal).
Clipping Level - The maximum electrical output signal level (dBV or dBu) that the microphone can produce before the output becomes distorted.
Close Pickup - Microphone placement within 2 feet of a sound source.
Comb Filtering - An interference effect in which the frequency response exhibits regular deep notches. Condenser Microphone - A microphone that generates an electrical signal when sound waves vary the spacing between two charged surfaces: the diaphragm and the backplate. Critical Distance - In acoustics, the distance from a sound source in a room at which the direct sound level is equal to the reverberant sound level. Current - Charge flowing in an electrical circuit. Analogous to the amount of a fluid flowing in a pipe.

-D-
Decibel (dB) - A number used to express relative output sensitivity. It is a logarithmic ratio.
Diaphragm - The thin membrane in a microphone which moves in response to sound waves.
Diffraction - The bending of sound waves around an object which is physically smaller than the wavelength of the sound.
Direct Sound - Sound which travels by a straight path from a sound source to a microphone or listener.
Distance Factor - The equivalent operating distance of a directional microphone compared to an omni directional microphone to achieve the same ratio of direct to reverberant sound.
Distant Pickup - Microphone placement farther than 2 feet from the sound source.
Dynamic Microphone - A microphone that generates an electrical signal when sound waves cause a conductor to vibrate in a magnetic field. In a moving-coil microphone, the conductor is a coil of wire attached to the diaphragm.
Dynamic Range - The range of amplitude of a sound source. Also, the range of sound level that a microphone can successfully pick up.

-E-
Echo - Reflection of sound that is delayed long enough (more than about 50 msec.) to be heard as a distinct repetition of the original sound.
Electret - A material (such as Teflon) that can retain a permanent electric charge.
EQ - Equalisation or tone control to shape frequency response in some desired way.

-F-
Feedback - In a PA system consisting of a microphone, amplifier, and loudspeaker, feedback is the ringing or howling sound caused by amplified sound from the loudspeaker entering the microphone and being re-amplified. Flat Response - A frequency response that is uniform and equal at all frequencies.
Frequency The rate of repetition of a cyclic phenomenon such as a sound wave.
Frequency Response Tailoring Switch - A switch on a microphone that affects the tone quality reproduced by the microphone by means of an equalization circuit. (Similar to a bass or treble control on a hi-fi receiver.) Frequency Response - A graph showing how a micro-phone responds to various sound frequencies. It is a plot of electrical output (in decibels) vs. frequency (in Hertz).
Fundamental - The lowest frequency component of a complex waveform such as musical note. It establishes the basic pitch of the note.

-G-
Gain - Amplification of sound level or voltage.
Gain-Before-Feedback - The amount of gain that can be achieved in a sound system before feedback or ringing occurs.
Gobos - Movable panels used to reduce reflected sound in the recording environment.

-H-
Harmonic - Frequency components above the funda-mental of a complex waveform. They are generally mul-tiples of the fundamental which establish the timbre or tone of the note. Hypercardioid - A unidirectional microphone with tighter front pickup (105 degrees) than a supercardioid, but with more rear pickup. Angle of best rejection is about 110 degrees from the front of the microphone.

-I-
Impedance - In an electrical circuit, opposition to the flow of alternating current, measured in ohms. A high-
impedance microphone has an impedance of 10,000 ohms or more. A low-impedance microphone has an
impedance of 50 to 600 ohms. Interference - Destructive combining of sound waves or electrical signals due to phase differences.
Inverse Square Law - States that direct sound levels increase (or decrease) by an amount proportional to the square of the change in distance. Isolation - Freedom from leakage; the ability to reject unwanted sounds.

-L-
Leakage - Pickup of an instrument by a microphone intended to pick up another instrument. Creative leak-age is artistically favourable leakage that adds a "loose" or "live" feel to a recording

-M-
Maximum Sound Pressure Level - The maximum acoustic input signal level (dB SPL) that the microphone can accept before clipping occurs.

-N-
NAG - Needed Acoustic Gain is the amount of gain that a sound system must provide for a distant listener to hear as if he or she was close to the unamplified sound source.
Noise - Unwanted electrical or acoustic energy.

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