Audio Abbreviations

by Curt Taipale

I often read questions in online forums about what certain terms mean. My article titled Are You Talking to Me? encourages tech types to exercise restraint in using “shoptalk” when they are communicating in particular with church staff who may be completely unfamiliar with those terms.

It occurs to me that this might be a good time to share some of the more common abbreviations and acronyms. So let's try a handful.

A MoM is a Minister of Music.

FOH means Front of House which, depending on the conversation, refers to either the main loudspeaker system covering the congregation, or the location of the mixing desk where that portion of the sound system is controlled from.

You may find that the terms FOH, Sound Booth and Production Booth are used interchangeably.

LAR stands for “Looks About Right”, an abbreviation that I created circa 1989 to identify the wholly inadequate (or just plain lazy) approach to designing a loudspeaker system without taking the steps and time necessary to do a proper design. Rather than building a computer model to prove out the choice of loudspeakers and their exact location and aiming angles, the novice designer eyeballs the situation and figures that putting a loudspeaker “about there” and aiming it “over here” should be adequate. Of course it never is.

DSP is an abbreviation for Digital Signal Processor. The process of optimizing the frequency response of a loudspeaker system involves at least an electronic equalizer of some kind. That could be a graphic equalizer, or preferably a parametric equalizer. We might also want to include a peak limiter in order to protect our loudspeakers from damage. And the moment the system includes balcony speakers or underbalcony speakers, or speakers in the lobby, you’ve just required the need for a signal delay. Years ago it was common to find such devices in the amp rack, typically involving multiple devices that may have required six to ten rack spaces.

Today we can install a digital signal processor that incorporates all of those devices (and more), all fitting within one or two rack spaces. Another significant advantage is that a digital signal processor is basically a specialized computer, and as such can be password protected to minimize unauthorized fooling around.

EQ is of course the equalizer. On a console, that would typically be the equalizer controls on each input channel or output channel.

MUTE – another term for the on/off switch.

PFL & AFL – Pre Fade Listen and After Fade Listen. Another term is “SOLO”. Pressing the button feeds the audio signal on that channel to a discrete listening buss. On a live sound console, that will typically be to the headphone output. On a recording console, it feeds the control room monitor loudspeakers. As the name implies, the signal from the PFL button is picked off before the channel fader, which may be before or after the channel EQ. The signal from the AFL button is picked off after the channel fader (which is also post EQ), so its level is determined by the position of the channel fader. The astute reader will realize that pressing the PFL button allows one to hear the audio signal on that channel without having the channel fader up, which can be a tremendous troubleshooting advantage.

VCA & DCA – Voltage Controlled Amplifier and Digitally Controlled Amplifier respectively. In a typical analog audio console, the audio signal travels through each channel fader. One can think of the fader as a volume control knob stretched out flat. As you adjust the fader, it varies the strength of the audio signal on that channel.

With a VCA console, the audio signal actually travels through a small audio amp inside the console. (One for each channel.) A DC voltage is used to adjust the gain of that Voltage Controlled Amplifier. So in this case the fader controls the amount of DC voltage being applied to the VCA’s control input, which in turn raises or lowers the strength of the audio signal going through the VCA. This offers the sound operator a number of advantages, but to stay out of the technical weeds I'll save that for another time. The DCA is found on digital audio consoles, and offers the same functional advantages as a VCA does for an analog console.

TRS is a one-quarter inch "phone plug" type of connector, typically used either for a balanced audio connection at the back of a console, or as the connector for a set of stereo headphones. For a balanced audio connection, the tip is the (+) positive connection, the ring is the (-) negative connection, and the sleeve is the "ground" or "shield" connection. When used for a set of headphones, the tip is the (+) positive connection to the left earpiece, the ring is the (+) positive connection to the right earpiece, and the sleeve provides the ground reference for both earpieces.

TS is a one-quarter inch "phone plug" type of connector used for unbalanced audio connections, commonly found on cables used to plug in electric guitars, electronic keyboards, and similar instruments.

XLR is a 3-pin connector generally used to connect microphones to a console and other balanced audio feeds. Pin 2 is the (+) positive connection, Pin 3 is the (-) negative connection, and Pin 1 is the "ground" or "shield" connection of the balanced cable. An excellent resource on the origins of the "XL" connector can be found here.

RTA stands for a Real Time Analyzer, a common audio measurement device that displays the sound energy present in discrete frequency bands. A simple Sound Level Meter only shows the overall sound level being measured, while an RTA displays the contribution of individual frequency bands that make up that overall sound level.

When we say “Aux” or “Aux Send”, we’re talking about a separate, independent mix of the inputs of an audio console. The Aux Send is typically used to send a mix of signals to a stage monitor, or to an effects device to add reverb.

DI stands for "Direct Inject", meaning that we plug the electronic instrument (bass guitar, keyboard, etc.) into the DI which then carries that audio signal directly to the console. Also known as a Direct Box.

AVL of course stands for Audio, Video and Lighting. You might hire a consultant to design the AVL systems for your new worship center, in which case that consultant will have experience with the design of each of those types of systems. An AVL system integrator has crews that are experienced with installing all three types of systems.

Labeling the Console Channels

Here is my personal console labeling system, most of which were stolen, ‘er, borrowed from fellow recording engineers and modified over the years.

PSO was created by my jazz piano teacher in college, his term for the pianos in the practice rooms which he called “piano-shaped objects” to denote their lesser quality. To this day, whenever I am labeling the inputs on a console that I’m mixing on, I typically label the grand piano inputs as PSO.

KEYS or KBD = electronic keyboard

SYZ = synthesizer

(I was never comfortable writing "SYN" on an input list.)

My labels for drum mic inputs include:

    Kick = bass drum
    SN = snare drum
    Rack 1 = first rack tom (might just be R1)
    Rack 2 = second rack tom (might just be R2)
    FL = floor tom
    HH = high hat
    OH = overhead (for the overall kit and cymbals)

BASS = bass guitar

GTR = a guitar (usually electric)

AC GTR = acoustic guitar

E GTR = electric guitar

WX = wireless mic (WX#9 is wireless mic #9)

PULPIT = hard name to shorten

PASTOR = “PSTR” looks funny on a scribble strip

SOP = soprano voice

ALTO = alto voice

TEN = tenor voice

BASS = bass voice

BAP = mic for baptism

VN = violin

VA = viola

CELLO = cello

DB = upright bass, aka double bass

TPT = trumpet

BONE = trombone

SAX = saxophone

TN SAX = tenor sax

A SAX = alto sax

TYP = timpani

PERC = percussion

A Little More Technical

T60 is an abbreviation for Reverberation Time, classically defined as the time it takes for sound to decay in a room by 60 dB after the sound is stopped (measured in seconds). Sometimes it is difficult or even impossible to measure 60 dB of sound decay, so you may instead see terms like T30 where we measure the first 30 dB of sound decay, and then extrapolate from there to determine how long it would take to decay the full 60 dB.

In designing a sound system you will often hear the word “speaker” used with different meanings. In one moment that may refer to a loudspeaker, while in another sentence that may refer to the “talker”, that is the presenter, the teacher, etc. In an effort to avoid confusion, it has become accepted practice to use the terms “loudspeaker” and “talker”.

NC. Sounds innocent doesn’t it? NC stands for Noise Criteria, and is a measure of background noise. If you are planning to build a new auditorium, you want to have a very clear agreement with the person who will be designing the mechanical systems for that auditorium, in particular the HVAC (heating, ventilation and air conditioning) system. Left to their own devices (and a meager budget), you may end up with an auditorium that has an HVAC system that is so noisy that you either have to turn up the loudspeakers to hear over it, or turn off the HVAC system during the pastor’s message. That may sound like an exaggeration, but I can tell you from firsthand experience it is not.

Not to confuse the issue, but RC stands for Room Criteria, a rating system for mechanical system noise that attempts to better define the expectations of the noise generated by such a system. For example, we might measure the noise and find an NC-30. On the face of that measurement we might determine that it would be an acceptable value for a worship center. On the other hand, let’s say that it measured an RC-30(R). That is essentially the same loudness of background noise from the HVAC system, but the “R” tells us that it has a prominent low frequency rumble characteristic which may be distracting during the message or quiet moments in the service. A suffix of (H) describes an HVAC system with audible “hiss” from air blowing over the fins of the vents. We would rather see an RC-30(N) which stands for “neutral”.

These may be too common to mention, but …

If someone says IMHO they mean "In My Humble Opinion".

ROFL means "Rolling On the Floor Laughing".

LOL is of course “Laughing Out Loud”.

IIRC means “If I recall correctly”.

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