Backwards Masking

Refers to the technique of putting material in recordings that can (usually) only be heard or deciphered when the recording is played backwards. The Beatles were one of the first groups to experiment heavily with this. There are a variety of things on some of their albums which, when played forward just sound like part of the music, but played backwards become a recognizable sound or vocalization.

Often times the sounds that are heard, even when the recording is played backwards, are so difficult to recognize that it is debatable whether they are just a coincidence or are an intentionally placed message of some sort. A number of artists have been accused of putting hidden satanic messages in recordings in this fashion, but little of it has ever been conclusively proven.

Baffled Stereo

When one is confused about how to mix in stereo and just mixes to mono instead. Actually it is really a generic term for a lot of different stereo miking techniques using an acoustic baffle to enhance the channel separation of the stereo signals. When placed between the two microphones in a spaced stereo set-up like ORTF stereo, DIN stereo or NOS stereo, the shadow effect from the baffle will have a positive influence on the attenuation of off-axis sound sources and thereby enhancing the channel separation. Baffles should be made from an acoustic absorbent and non-reflective material to prevent any reflections on the surface of the baffle to cause coloring of the audio.

Balanced

In audio, the opposite of Unbalanced. For us balanced refers to a type of AC electrical signal having two "legs" independent of ground. One is generally considered positive (+) and the other negative (-) in voltage and current flow with respect to ground. Unlike unbalanced audio lines there is no "signal" carried in the shield or ground connection unless there is a fault. The main benefit is that any noise that gets induced into the line will be common to both the positive and negative sides and thus canceled when it arrives at its destination, assuming the destination is balanced. This phenomenon is called "Common Mode Rejection" and basically just means that any signals common to both the positive and negative legs of balanced lines get canceled. This happens because when the receiving device looks at the signal the common noise actually shows up as out of phase with itself, and gets cancelled. Think of it as if the negative (-) signal gets inverted to positive (+) before use, which puts the desired audio signal in phase with the already positive other leg and at the same time causes the undesired common noise to become out of phase with itself. Clear as mud? Balanced lines are generally much better for long cable runs due to their ability to reject induced noises. XLR and TRS type cables are designed to transmit balanced audio from one balanced device to another. A standard 1/4-inch guitar cable is an example of an unbalanced cable. Another (newer) application of balancing that is becoming popular in audio systems is the idea of balanced power systems. Fundamentally the concept is the same. There is a positive and negative (with respect to ground) leg of electricity at every electrical outlet. The idea is that the power supply of any devices connected can then reject any noise induced on the AC line and thus will produce cleaner audio. We'll talk more about balanced AC systems in the future.

Banana Plug

An electrical connector designed to join audio wires such as speaker wires to the binding posts on the back of many power amplifiers or to special jacks known as (surprise) banana jacks. A common configuration of banana plugs is to have two of them molded together and spaced 3/4 of an inch apart, which also happens to be the spacing of the binding post receptacles on the back of power amps. This assembly is commonly called a banana plug, but the more technically correct term is "double-banana plug," or it is sometimes called a "GR" plug, after the General Radio Corporation, which introduced it many years ago.

Bandwidth

Literally, bandwidth is a frequency span. Beyond that definition, its meaning will depend somewhat on context. For example, the bandwidth of a bandpass filter is the upper cutoff frequency minus the lower cutoff frequency (cutoff frequency being the filter's -3 dB point). The audio bandwidth is generally given as 20 Hz to 20,000 Hz, although there are harmonic components of audio that extend far above the 20k point. In most situations where bandwidth is given as an audio spec, the wider the frequency range the better. Be sure that when comparing bandwidth on different devices, that the same spec is being expressed. For example, some effects devices cite their bandwidth spec based on the dry, or unprocessed signal, while others give the bandwidth of the actual processed sound. These difference between these two specs (both listed as "bandwidth") can be substantial!

Bank Select

A special set of MIDI messages designed to allow programs to be recalled from multiple banks of MIDI instrument. The MIDI specification was originally developed to access up to 128 programs using the Program Change message (0Ð127). At that time (mid 1980's) no synthesizer held more than 128 sounds, but as technology advanced rapidly in the early 1990's and RAM prices decreased, we found more and more synthesizers with greater than 128 patches. The MIDI Association recognized this problem and developed a new MIDI command called the Bank Select Command. The Bank Select command is made up of two messages: Continuous Controller 0 (Most Significant Bit or MSB) and Continuous Controller 32 (Least Significant Bit or LSB). Continuous Controller messages are often abbreviated as CC (For example: CC0 and CC32). Having two messages allows you the ability to access up to 16,384 banks, each with 128 patches for a total of 2,097,152 patch locations! Unfortunately the MIDI Association left the implementation of the Bank Select commands up to the synthesizer manufacturers and each company implemented it differently. Some synthesizers require both CC0 and CC32 while others require one or the other. You must check your synthesizer's MIDI implementation chart to determine what message your machine needs.

Bantam

A word used to describe patch bays or cables. For all practical purposes it has the same meaning as TT (Tiny Telephone). Western Electric/AT&T invented the Long Frame plug for switchboards, that's why it's called a 'phone' plug. Switchcraft invented the Tini Telephone and registered Tiny, Mini, TT, etc. In the 1960's, ADC was formed by a group of x-Soundcraft employees and they needed a name which would not infringe on Switchcraft's trademark. The Bantam boxing class was the source for the name. Switchcraft now uses the terms "Bantam-Type™", "TT™" and "TT-Jax™" in the same sentence.

Bass Reflex

A type of speaker cabinet design. Bass Reflex cabinets use an opening, or port, in the speaker cabinet to enhance bass frequencies. The idea is that the sound pressure generated by the back of the woofer (inside the cabinet) is routed out the port, where it is mixed with the sound coming from the front of the woofer. By careful design of port size and position, the amount of low frequencies and how low they extend can be greatly modified.

Baud Rate

The transmission speed (or rate) of a modem. Named for French telegrapher Emile Baudot, who developed a five-level telegraph code. Baud rate is roughly one half dot cycle per second in Morse code, one bit per second in binary signals, or other values depending on the coding system used. Note that baud rate is not the same thing as bit rate, although the two are often used interchangeably - with a modem, its baud rate can be quite different from its bit rate.

You'll often see MIDI specified as 31.25 KBaud. Technically, this is not correct. The spec should actually be a bit rate of 31,250 bits per second.

Beats (or "Beating")

The result of combining two sounds less than 30 Hz or so apart in frequency together, beating is the alternate reinforcement and cancellation of amplitude in the combination sound (over around 30 Hz in difference results in an rougher "out of tune" sound, rather than distinct beats). Most easily heard when the original sounds are of equal volume, the frequency of the beats will be the difference in frequency between the two signals. Beats are common in most musical instruments, and are often used for tuning; when the instruments are in tune, beating disappears. When complex sounds are combined, beating occurs between various partials in the signals - listen to a piano for a good example of this. Beating is not restricted to musical instruments, it can occur between any two signals or sounds. A good example: We were recently subjected to an extended airplane trip in a small twin engine prop-driven plane. The pilot never did manage to completely "tune" the two engine's speeds to where they were completely beat-free...

Bias

On tubes, bias is a small direct voltage applied to the grid to move the operating point of the device into a more linear range so as to reduce distortion.
On FETs, bias is a small direct voltage applied to the gate to move the operating point of the device into a more linear range so as to reduce distortion.
One bipolar transistors, bias is a small direct current applied to the base to move the operating point of the device into a more linear range so as to reduce distortion.
In magnetic tape recorders, bias is a very high frequency signal (often in the 100 kHz or higher range) mixed with the audio signal during recording. The purpose of bias is to reduce distortion by rapidly saturating the tape in both directions, minimizing the time spent in its non-linear magnetic hysteresis (see the WFTD Archives) curve. In more basic terms, bias makes it easier for the tape to respond to the audio signal in a linear fashion, and reduces distortion.

In all cases, the level of the bias must be carefully adjusted to achieve the best results. Too little bias increases distortion, too much reduces signal level and diminishes high frequencies.

Binaural

A system of recording with a plastic replica of the human head, with microphones placed in the ears, replicating as near as possible human hearing functions regarding phase, directionality etc. This signal information is absent from ordinary microphone pickups. Signals from the two mikes placed in each ear of the dummy head are kept entirely separate all the way to the two drivers of the final listener's stereo headphones. The result is a convincing preservation of the 360° soundfield and localization abilities present where the dummy head was placed.

Binding Post

A type of electrical terminal, a binding post is most commonly found as the output connector on a power amplifier, or as the connectors on a speaker cabinet. A binding post is a very versatile connector, accepting banana plugs, alligator clips, bare wire, and others. Generally, binding posts are color coded, with the black connection going to ground, and the red connecting to hot. Binding posts offer fast, easy connections, and provide reasonably good surface area contact for good conductivity.

BIOS

An acronym for Basic Input/Output System. Mostly germane to PC compatible computers, this is usually an EPROM with computer program instructions in it. A computer motherboard BIOS controls how the hardware is defined and the basic functions of the computer (such as controlling the keyboard, monitor, etc.). With a SCSI host adapter, its BIOS is used to control SCSI hard disk drives and perform the boot function. If a host adapter does not have a BIOS, then hard disk drives controlled by that host adapter cannot be used to boot from (booting must be done from another source, such as floppy, IDE, or another SCSI host adapter with a BIOS). Hard drives can have their own BIOS as well, which defines their operation. The BIOS can also contain useful software utilities, and in some cases, can be reprogrammed or updated via software to accommodate new hardware. Older PC computers often have to have their BIOS updated in order to properly work with new hardware.

Bi-phase Sync

Bi-phase is an older synchronization technology used in the film industry. Typically, the clock was derived from a box that hung off of large film mag recorders. This box emitted a pulse that allowed sync. Working with pulses alone, bi-phase sync did not provide location information, making it a rather limited solution. (Anyone remember working with MIDI clocks before Song Position Pointer and MIDI Time Code was introduced? The situation was similar...)

Bit

A contraction of "binary" and "digit", a bit is a number used in a digital information system. A bit is easy to deal with in electronic terms, having only two values, 0 and 1, alternatively expressed as "off" and "on"; "low" and "high", or "absence of voltage" and "presence of voltage". Bits are commonly grouped into binary "words" or bytes.

Bit Mapping

The action of rearranging digital data in such a way that much of the information that would require a larger digital word can be encoded into a word of lower bit depth, thereby producing a higher quality signal than what would normally be possible for the given bit depth. This is distinct from dithering (see WFTD archive dither) which is more of a randomization of the signal at low levels. A popular bit mapping scheme right now is Sony�s Super Bit Mapping, which claims at least 20 bit performance on 16 bit recordings.

Black Burst

Also sometimes called video sync or house sync, black burst is a blank video signal. In other words it is a video signal with no picture data. It is just black. In video editing situations it has always been important for all video decks and cameras to be "gen locked," which means that their video clocks are all synchronized. They don't always have to be at the same location (which would be addressed by SMPTE Time Code), but they do have to be frame locked which means that they are moving from one frame to the next in precise synchronization. This is critical for combining (editing) video data. An easy way to achieve this is to have a master time base that all of the other equipment slaves to for synchronization. In video the relevant time base is the frame rate of the video, and thus black burst is used. As audio people began to do work for video it also became important for them to be synchronized to the exact frames of video (especially for digital audio work) so they also became acquainted with and now use black burst generators. A black burst generator is often a simple little box with one or more video outputs. The outputs simply supply an accurate, and more importantly common, source for the timing of all equipment in the studio. Thus they also are named house sync generators.

BLER

Abbreviation for Block Error Rate. In CD production (and on hard disks) data is written into a series of blocks. A block usually contains 512 or 1024 bytes of data. BLER refers to how many blocks per unit of time are in error or can't be read. BLER is inversely proportional to the readability of a disc. That is, the more block errors the more difficult the disc is to read.

Block

In audio and computing the term block merely refers to a segment of data. It is significant because digitized data is often stored in blocks of a predetermined size (often 512 or 1024 bytes). For example, a disk might be formatted to hold data in blocks that are 512 bytes in size. That means if you have a packet of data to be written that is 1,047 bytes long it will require 3 blocks to store it, even though the third block is technically almost empty. This empty space can not be used by any other data. This block method of data storage and retrieval is key to making it easy for computers to be able to quickly locate specific data on disks and other storage media.

Blumlein Microphone (or Blumlein Pair)

Named for Alan Blumlein (chief engineer at EMI in London during the 1930's, and a pioneer in stereo audio), a Blumlein pair uses two coincident bi-directional (or figure 8) pattern microphones set up at 90 degrees to each other. This stereo miking technique provides a strong center image, and good room ambience. When using this technique, absolute polarity in the entire audio system is essential, mic distance from the source is critical in balancing ambience with direct sound, and since so much ambience is captured, a good sounding room is critical. (See also WFTD "Coincident")

BNC

A type of coaxial connector often found on video and digital audio equipment, as well as on test devices like oscilliscopes. In audio gear, BNC connectors are normally used to carry synchronizing clock signals between devices. BNCs are bayonet-type connectors, rather than screw on, or straight plugs. They are named for their type (Bayonet), and their inventor, Neill Concelman.

Boot

Besides being an article of footwear, boot refers to the process of starting up a computer system, or any device with a CPU. It is spoken as to "boot up," or "booting up." Basically this is a colloquialism that comes from the idea of pulling itself up by its own bootstraps. A computer booting up generally goes through a series of self-tests and loading operational system instructions.

Bouncing

The process of combining several tracks together and re-recording them onto another track is called bouncing. This is normally done to free up tracks for more recording. For example, you might have three background vocals recorded on tracks 1 to 3. By combining these tracks with a mixer, and routing them to track 5 (for example) tracks 1 to 3 can be erased and used to record other materials. Keep in mind that bouncing does require that you pre-decide on levels, EQ, etc. for the tracks being bounced - once they are combined, it is impossible to adjust their relative levels (overall level and EQ of the bounced track can, of course, still be adjusted).

BPM

Abbreviation for Beats Per Minute, it is the standard way in which musical tempos are denoted, especially for use in electronic music composition tools like sequencers. 120 BPM means that in one minute there will be 120 musical beats regardless of any other variables such as time signature.

Breathing

In audio terms, breathing is the change in audible level of background noise due to use of noise reduction or other processing. If the processing is not set up correctly, background noise will tend to "jump up" in level during breaks in program material.

Brickwall Filter

Some low pass filters are designed with such a steep cutoff slope that they resemble a "brick wall." These types of filters have often been used as anti-aliasing (see WFTD archive Aliasing) filters for A/D converters (see WFTD archive A/D Converter). Designers prefer not to use them because their severe nature often has negative side effects on the unfiltered audio such as phase shift and non linearity near the cutoff point.

Bucking

Refers to the cancellation of one signal or frequency component of a signal by another signal of equal amplitude but opposite polarity. Sometimes this is called phase cancellation. It also is a phenomenon that is part of the sound of a phaser or flanger. As they sweep through their range various frequencies are accentuated or (nearly) cancelled producing their characteristic "whooshing" effect. Hum bucking, as in hum bucking guitar pickups, is the bucking of frequencies we associate with hum (60 Hz in the United States). In this case the cancellation is of EMI that is being picked up by the guitar's pickup, which is acting as a transformer picking up various fields nearby.

Buffer

A temporary storage area for data being transferred from one place in a system to another, or to another system. Buffers are often used in the context of computers reading from and writing to various disk drives, but can come in to play on most any type of data transfer. Buffers are needed because it often occurs that one or both of the devices cannot maintain an exact and synchronized data transfer rate. Buffers provide a place for data to sit while one of the devices catches up to the other. Cache (see WFTD archive Cache RAM) is a type of buffer.

Bus

In audio (not transportation) terms, a Bus is a point in a circuit where many signals are brought together. For example: Most electronic items have a Ground Bus where all of a device's individual ground paths are tied together. In mixers, we have Mix Busses, where multiple channels' signals are brought (or blended) together; Aux Busses, where feeds from channels are brought together to be routed to an external processor or monitor send, etc. In general, the more busses a mixer has, the more flexible the routing capabilities of that mixer will be.

Bus Bar

Typically a long rod of copper (or other conducting metal) used to ground multiple devices to a single point. The respective devices ground to the Bus Bar which, in turn, grounds to a single location. This technique is commonly used inside mixing boards to provide a good ground contact through the length of the desk.

Byte

In digital data bits are arranged into what is known as "words." A byte is a binary word that is 8 bits long. A kilobyte (Kb) contains 1024 bytes (not 1000). This is because 1024 is a power of 2, which is the basis for binary digital data.