A

Amplifier:
A device that increases the level or amplitude of an electrical signal, making the resulting sound louder.

B

Bandwidth:
In signal processing, bandwidth refers to the usable frequency range of a communication channel, measured by the difference between the device’s highest and lowest usable frequencies.

Bass:
The lower range of audio frequencies up to approximately 250 Hz. A reference value.

Bit:
The smallest unit of digital information representing a single “0” or “1.”

C

Cable:
A group of one or more insulated conductors, optical fibers, or a combination of both within an enveloping jacket, typically for transmitting electrical signals of different types.

Cable Assembly:
Cable that is ready for installation in specific applications and usually terminated with connectors.

Cable Harness:
A grouping of cables or wires used to interconnect electronic systems.

Cable Sheath:
Conductive protective cover that is applied to cables.

Capacitor:
An electronic device made of two plates separated by an insulator, designed to store electrostatic energy. The capacitor is a key component in condenser microphones, for example.

D

D/A:
Abbreviation for Digital to Analog conversion, which changes digital data numbers (digital audio signal) into discrete voltage level. The reverse process of A/D.

Damping Factor:
Describes an amplifier’s ability to restrain the pushback motion (back-EMF) of the loudspeaker cone when the audio signal stops.

dB:
An abbreviation for decibel, a measurement ratio that compares signal strengths (usually audio levels).

Diaphragm:
The part of a microphone that moves in response to sound waves, converting them to electrical signals.

Dolby:
The brand name of a manufacturer of noise reduction systems and other audio systems, to improve performance and fidelity of audio recording, playback, and transmission.

Dynamic Range:
1) The ratio (in dB) between the loudest peak and the softest level of a song or recording. 2) The ratio (in dB) between the softest and loudest possible levels a device or system can provide without distortion.

E

Electromagnetic Field

(Abbreviated EMF) A field of magnetic energy put out because of current traveling through a conductor.

Electromagnetic Interference (EMI)

The bane of audio professionals everywhere, EMI is a type of interference caused by nearby electromagnetic activity, which can be picked up by audio cables and equipment, causing unwanted noise, hum or buzz in audio systems. Common causes of EMI in audio systems may include high-current power lines, fluorescent lighting, dimmer switches, computers, video monitors and radio transmitters.

Electrons

Negatively charged particles revolving around the nucleus of an atom. Electrical current is generated by electrons moving along a conductor, like a metallic wire.

F

Fidelity

A term describing how accurately a sound is reproduced from its original source.

Frequency

The number of occurrences of a particular event within a certain amount of time. In audio and acoustics, frequency specifically refers to the number of complete cycles a vibration or waveform makes in a second, measured in cycles per second, or Hertz (Hz). In sound, frequency determines what we hear as pitch. The longer the wavelength, the fewer the cycles per second, and the lower the pitch.

Frequency Range

1) The range of frequencies over which an electronic device puts out a useful signal (see also “Bandwidth”). 2) The range of frequencies that can be substantially transmitted or received in relation to a sound source. Each instrument has a certain frequency range in which it can play; the human ear can also hear within a certain frequency range.

Frequency Response

The range between high and low frequencies that a component of an audio system can adequately handle, transmit or receive.

G

Gain

1) The amount of increase in audio signal strength, often expressed in dB.

H

Harmonic Distortion

The presence of harmonics in the output signal of a device which were not present in the input signal, usually for the purpose of changing the instrument’s timbre.

Headroom

The difference in dB between normal operating level and clipping level in an amplifier or audio device. Also describes the difference in dB between the peak levels of a recording and the point at which the signal distorts. (Also called “Margin.”)

Horn

1) A speaker or speaker enclosure where sound waves are sent by a speaker cone or driver into a narrow opening which flares out to a larger opening. 2) One of several different types of brass musical instruments.

Hum

1) The low-frequency pitch that occurs when power line current is accidentally induced or fed into electronic equipment. The hum reflects the fundamental frequency of the current (60 Hz in the U.S., and 50 Hz in many European countries). 2) To vocalize a pitch without opening one’s mouth.

Hz

An abbreviation for the term Hertz, or the unit of frequency.

I

Imaging

Refers to the ability to localize a specific sound within the sound space. In recording environment, it refers to “placing” instruments within the stereo or surround field so that it when the sound is played through speakers, it fools our ears into thinking the sound source is in emanating from a specific point instead of from the speakers. In live audio and sound reinforcement, the principle of imaging is the same, the goal being to make the audience perceive the sounds as coming from performers on the stage, rather than from the speakers.

Impedance

Refers to the resistance of a circuit or device to alternating current, which can be mathematically described as the ratio of voltage to current. Differences in impedance between devices in the studio can affect how they work together. Impedance is abbreviated by the letter Z, and measured in ohms (W).

In Phase

The desirable situation in which two or more devices (and their respective audio signals) are on the same side of the polarity spectrum, producing waveforms that do not conflict or cancel each other out.

Inductance

A characteristic of electrical conductors in which electrical charge (voltage) is produced or stored magnetically due to the natural resistance to change in the electrical current. Inductance is an electromagnetic principle that can either assist in audio applications (as in loudspeakers) or cause resistance (as in using speaker wire whose gauge is too low for the application).

Inductor

A device (usually a coil of wire) that converts electrical energy into stored magnetic energy as electrical current passes through it. Commonly found in a variety of audio applications such as guitar pickups and loudspeakers.

O

Octave

An interval or difference of pitch of 12 half-steps. In our standard tuning system, the higher note in an octave is exactly double the frequency of the lower note.

Ohm (W)

The unit used to measure the amount of opposition (impedance) to electrical current flow in a signal or device. (See also “Impedance.”)

Ohm's Law

The mathematical relationship between voltage, current and resistance.

Open Circuit

An electrical circuit that is disconnected, interrupted or incomplete, preventing the flow of electricity.

Oscillator

1) A tone generator in a synthesizer. 2) A device that puts out test tones at various frequencies.

Out of Phase

1) Being similar to another signal in amplitude, frequency and wave shape but being offset in time by part of a cycle. 2) Having the opposite polarity.

Output Impedance

The opposition to the flow of electrical current by the output circuits of an amplifier (or other device).

Output Level

The signal level at the output of a device.

P

Pass Band

The frequency range of signals that will be “passed” by a filter, rather than reduced.

S

Shielded Cable

Cable that has a shield around an inner conductor or inner conductors.

Short (Short Circuit)

A direct connection between two points in a circuit that (usually) should not be connected.

Sine Wave

The waveform of a “pure tone”—a sound vibrating at a single frequency. Depicted graphically, a sine wave is a smooth, oscillating curve.

Solid State

In electronics, refers to the use of transistors and semiconductors (solid materials) in the building of electronic devices, as opposed to tubes. In the recording studio, solid state amplifiers have different properties than tube amps, and each has its own advantages and disadvantages. A more recent application of solid state construction is in computer devices, particularly solid state hard drives (SSD), which transfer data more quickly than conventional spinning disc drives, and are less prone to breakage.

Speaker

A device that converts electrical signals to sound; more technically, a transducer that changes an electrical audio signal into sound pressure waves.

Square Wave

A wave shape in which the voltage rises instantly to one level, stays at that level for a time, instantly falls to another level and stays at that level, and finally instantly rises to its original level to complete the wave cycle.

Standing Wave

An unwanted sound wave pattern that often occurs when the sound wave bounces between two reflective parallel surfaces in a room, and the reflected waves interfere with the initial wave coming from the sound source, in which the combined wavelength of the affected frequency is effectively the length of the room. This creates the audible illusion that the wave is standing still, so the frequency is amplified to an unwanted level in certain parts of the room while nearly absent in others. Standing waves are most common in square or rectangular rooms with parallel surfaces, so acoustic designers try to prevent these waves by installing absorptive materials or introducing other items to offset the parallel surfaces.

Stereo

A recording or reproduction of at least two channels where positioning of instrument sounds left to right can be perceived.

Stereo Image

The audible perception of stereo, in which different sounds sources appear to be coming from far left, far right or any place in between.

Surround Sound

A technique of recording and playback in which the listener hears various aspects of the sound from front to back as well as side-to-side—a 360-degree audio image, as opposed to the standard stereo left-right image. Surround sound can occur in various formats with different numbers of speakers arrayed through the room. Surround sound today is most commonly used in film and TV production.

T

Tweeter

A speaker designed to reproduce only the higher frequencies of the sound.

Two-Way Speaker

A speaker system with separate speakers to reproduce the lower frequencies (woofer) and the higher frequencies (tweeter).

V

Vacuum Tube

A diode, a glass tube with the gases removed, through which electrical current can flow. In audio, vacuum tubes are used in amplifiers, oscillators, and other analog devices.

Voltage

The difference in electrical force or pressure (“potential”) between two objects, causing a flow of electric current between them.

Volume

A common, non-technical term that either refers to sound pressure level (which we hear as loudness), or to audio voltage level.

VU Meter

A meter that reads audio voltage levels in or out of a piece of equipment and is designed to match the ear’s response to sudden changes in level.

W

Woofer

A speaker that is designed to reproduce bass frequencies only.