ACS - Church Audio & Acoustics Glossary

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backfeed
balance

The condition of having an equal weight of different instruments and/or voices so no one instrument or voice overpowers the others. A mix is considered to be "balanced" when all of the sounds can be heard clearly and no one sound dominates the rest (exception: when there is a lead instrument or vocalist, they will typically be louder than the others).
balance control

Typically found on consumer-level amplifiers, this knob allows the user to select the right or left channel or anywhere in between. The normal position is straight up; when turned to the right (clock-wise) the right channel will remain the same volume while the left channel will be slowly faded out. Turning the knob to the left (counter-clockwise) from the center point produces the opposite effect. A similar control is found on the input channels of a mixer.
see also pan
balanced

A wiring method using three individual wires for a single audio signal. One wire is a ground/drain/shield wire, another carries a positive audio signal, the third carries a negative audio signal. The two audio signal wires carry the same (equal) signal, but the signals are oposite polarity of each other. At the terminating end, the two signals are inversely combined (one of the signals is inverted and then the two signals are summed). Why do this? Electromagnetic interference is inducd equally on both wires--this would normally result in a noisy audio signal. Since one of the signals is opposite polarity (and is reversed when the two are summed together), the interference now cancels out because if two signals are equal but opposite in polarity, they will cancel when summed together. Balanced lines are used for microphone and line level signals.
see also unbalanced
banana plug

see MDP connector
band

1. A musical group
2. A defined portion of either the audio or radio frequency spectrums. A specific part of the frequency spectrum such as AM, FM, VHF, UHF, etc.
bass

Low audio frequencies. Often found when labeling consumer-level equalizer controls.
beat

The steady pulse in music.
beats

What occurs when two sounds mix together and cause a regular rise and fall in volume. This is most often heard in a band or orcehstra during tuning. An instrument known to be in tune plays the same note as a second similar instrument. If the frequency is the same, the sounds will combine well. If the second instrument is out of tune from the first, a rhythmic beating of the sound will be heard.
Bel

One Bel is the amount of change in the power applied to a system that a person can detect. It's a ratio of power difference, not a fixed value. When the ratio involves standard units of reference, fixed values can be derived. It's a measure of watts (power), not voltage. A Bel is usually too large of an increment, therefore the Decibel (1/10th of a Bel) is commonly used.
BetaSP
biamped

A speaker system that's fed by two separate signals. One signal contains all of the low-frequency material (feeds the woofer), the other signal contains all of the high-frequency material (feeds the horn). An active crossover is used to split a full-spectrum audio signal into the two parts, then separate amplifiers are used to power the woofer (low) and the horn (high).
see also active crossover; passive crossover
bias voltage

A fixed DC voltage which establishes the operating characteristic of a circuit element such as a transistor.
bidirectional microphone

A microphone that picks up sound equally from two directions. A good example of this type of microphone would be if you were able to put two cardioid microphones back-to-back. The resulting microphone would pick up sound from two directions and reject sound from the sides. It’s common to see such a microphone used for recording or braodcast applications. Typical specifications are: coverage angle=90-degrees (each side), maximum rejection=90-degrees (2-points)
see also: cardioid; hypercardioid; omnidirectional; supercardioid; polar pattern
bing-bang

Sound energy moving about in a most harmful and out-of-control acoustical manner (Barry Birdwell, Birdwell Acoustics, Inc.)
blocking
blurb
blurp
board

see mixer

bodypack

A wireless transmitter style which can be worn on the body. The bodypack usually contains the battery, transmitter, and is clipped to a piece of clothing. It's what a wireless lapel/lavalier microphone is connected to.
boom

1. A loud, explosive noise heard through a sound system that can be produced by many different actions.
2. A stand for a microphone. A boom stand can be described as being a normal straight stand with an adjustable arm at the top. The arm can be positioned at any horizontal angle and allows a microphone to be held several feet from the base of the microphone stand. Boom stands are used to mic a drum kit from overhead, a guitar, pianos, etc.
boost

To increase or amplify. Usually refering to a control capable of increasing or amplifying a signal.
see cut
boundry microphone

A microphone designed to be placed on a surface (boundry) such as a wall, floor, or sheet of plexiglass (or similar). Microphones like this pick up the sound directly before it's reflected off the surface. The size of the surface determines the lowest frequency the microphone will pick up.
braided shield

A type of cable where the center conductor(s) are surrounded with strands of wire that are braided together. This braid, or mesh, is the shield that protects the signal on the inner wire(s). Shielding is only about 90% (a foil shield is 100% coverage).
bridged mono

A setting on a two-channel power amplifier that joins the two inputs as well as the two outputs. The two individual amplifiers function as a single amplifier in a push-pull configuration. Most often this is done to increase the power output of the amplifier. Be sure to read and fully understand the instruction manual on the particualar unit you're doing this on or damage will result.
broadcast

To transmit a signal to a different location. Common use is in radio and television broadcasting where the audio (and picture in television) is transmitted through the air on radio-frequencies (RF).
bright (sounding)

The condition when an audio signal contains a lot of high frequencies. Often the signal is very clear and easy to understand, although not too natural sounding.
burst

The set of high-frequency pulses at the beginning of each line of video. These pulses determine the phase of the color signal. (also what happens when an inflated balloon is touched with a sharp pin.)
bus assignment switch

see assign
buzz

An unintentional rapid repeating of a popping noise. Most often caused by a ground loop or improper grounding techniques. The sound can be a single low frequency, multiple higher frequencies (harmonics), or any combination of the two. Buzzing created by a grounding problem is often difficult to isolate.
see also ground loop