R

RAID

An acronym for Redundant Array of Independent Disks. Sometimes you will see the word Inexpensive in place of Independent, but the basic point is the same: Multiple drives doing the work of one drive, but with redundancy. The term was coined in 1987 by researchers at the University of California at Berkeley to describe a series of redundant architectures used in fault-tolerant disk arrays (RAID levels 1 through 5). It was originally developed as a way to organize small format disk storage devices to dramatically increase input/output (I/O) speed and improve data availability. At its simplest, a RAID-1 array consists of two drives that store identical information. If one drive goes down, the other continues to work, resulting in no downtime for users. RAID-1 isn't a very efficient way to store data, however. To save disk space, RAID-3, -4, and -5 "stripe" data and parity information across multiple drives (RAID-3 and -4 store all parity data on a single drive). If a single disk fails, the parity information can be used to rebuild the lost data. Unfortunately, there is a performance trade-off: depending on the RAID type used, a RAID will be slower than a single drive at either reading or writing data. In demanding audio or video applications, however, a properly configured RAID system can actually increase bandwidth (speed) while improving reliability.

RAM

Okay, back to the basics today. RAM - An acronym for Random Access Memory. A generic for chips that are used in computing devices to store sets of instructions, which can be computer programs and data or, in the case of some musical equipment, audio data. When you run an application like Microsoft Word, the program is called up from its permanent storage area (like the hard drive, floppy disk, or Cd_ROM) and moved into the RAM, where the CPU has much faster access to it. Data can be manipulated and calculations performed very quickly and then saved back to the storage medium. Sometimes RAM is just used as a buffer between subsystems or as a cache. There are many different types of RAM (DRAM, SRAM, EDO RAM, etc.) and each has its unique properties and price/performance characteristics. RAM is usually purchased by consumers as a small circuit board (often inaccurately called RAM chips) that are made of actual RAM chips and other components. These boards can be installed in computers and other devices to expand their available memory. Because of the widespread use of RAM in all sorts of devices the prices have dropped significantly in the past decade while the quantity of manufacturers and distributors has risen. RAM circuit boards can vary widely in quality and cost. There are many subtle and not so subtle factors that go into making very high quality RAM boards so it is a good idea to be careful when purchasing RAM.

Random Access

As opposed to linear access, where data or items must be accessed sequentially (like on a cassette tape), random access allows you to randomly jump to any item on a piece of media, and retrieve or operate on it immediately (like a CD, or hard drive). The biggest difference is in the speed with which items can be accessed. By allowing you to "skip" to the item you want, random access greatly increases speed and productivity.

RAR

Abbreviation for Read After Read. Many helical scan decks recording digital data perform a read after write operation to ensure that the data written to tape reads back correctly. This is part of the error protection. In some high end models (such as the ubiquitous Sony 1630) a read after read is performed which gives double assurance of data integrity on the tape.

Ratio

In a compressor, limiter, or expander, ratio is the amount of output level change that results from a given input level change. For example, in a compressor with a 4:1 ratio, an input level increase of 4 dB will result in an output increase of only 1 dB. An expander might have a ratio of 1:4; for a 1 dB input change, a 4 dB output change will result. Limiters typically have extremely high ratios, some claiming infinity:1, which essentially means that for virtually any input level increase, there will be only a very minor output level increase.

R-DAT

Abbreviation for Rotating Digital Audio Tape as opposed to S-DAT which stands for Stationary Digital Audio Tape technology. R-DAT just refers to what we have all come to know and love simply as DAT. The "R" was originally placed in front of the name because there are some S-DAT systems out there and there needed to be a distinction between the two. R-DAT machines handle tape and record pretty much the same way a modern VCR does (so do ADAT machines for that matter). The tape moves somewhat slowly while the rotating head spins at about 2000 R.P.M. (revolutions per minute) recording the data on the tape in a helical scan fashion, which provides a much higher "effective" tape speed.

Real Time Analyzer (RTA)

An RTA is a device which uses a number of narrow bandwidth filters connected to a display to give a visual indication of the amplitude in each frequency band. RTA's are useful for getting a reading on how a room will subjectively sound, where problem frequencies might be, and how to approach EQ'ing to correct for those problem frequencies.

Red Book

The Red Book specifies the standards for audio compact discs. Jointly developed in 1983 by Philips and Sony, it contains detailed specs on physical and optical characteristics, and logical organization (table of contents, track, and audio stream formats). The Red Book is the primary compact disc specification, all other formats are derived from it.

Refurbished

We break outside of our normal WFTD for today to respond to some inquiries about what refurbished really means. Basically it is any product that fails quality control and must be "re-manufactured" to meet the specified standards. This can include cosmetic flaws as well as operational issues that need to be corrected. Re-manufacturing can be simply applying a dab of touch up paint or installing a whole new internal assembly. Refurbished products typically (though not always) have a manufacturer's warranty and are often the next best thing to a genuine new product.

Regeneration

Also called "feedback," among other things, regeneration is signal fed back through an effects processor to intensify, or extend an effect. For example, in a delay effect, signal passes through the processor, is delayed and sent out as an echo of the original sound. If some of the delayed signal is tapped off and sent through the delay circuit again, a second repeat will result. By increasing the amount of signal sent back through (or fed back, or regenerated) the number of repeats is increased. Another example: On a flanger, when signal is regenerated through the flanging circuit, the effect becomes more deep, or intense.

Reset All Controllers

A MIDI message used to return all continuous controller values such as pitch bend, modulation, and aftertouch to their zero or default settings. It is not uncommon in live performance and/or complex sequencing for one or more controllers to be left in a state that can cause the next patch used to sound strange. Many sequencers issue a Reset All Controllers message upon playback to help avoid this.

Resistance

A measurement of the opposition of a body or substance to current passing through it. Resistance causes a change of electrical energy into heat or another form of energy. All electrical circuits and wires have some resistance to the passage of electricity. The unit of the resistance is the ohm (¸), named after George Ohm, who formulated Ohm's Law. Impedance, a special case of resistance for AC signals, also uses the ohm as its unit of measurement.

Resolve

This word has many uses and subtly different meanings. There are two that pertain to audio. Resolve in the musical sense refers to causing a chord or series of chords to progress from a state of relative dissonance to a state of relative consonance. In audio production resolving relates to synchronization. Even in the relatively finite domain of synchronization the word gets used in a variety of contexts. When two tape machines are in synchronization with one another they can be said to be resolved, but in general it means that a time code is matched to some reference, whether that is some other time code source or a master clock of some sort. When time code is being recorded to a machine as an exact reference to time code already existing on another machine that code is said to be resolved. If the SMPTE track on a video deck is in exact synchronization (in terms of frame rate/speed) with the black burst video sync it is said to be resolved time code.

Resolution

There are many definitions, but the relevant one for our purposes is that resolution is a measurement of the fineness of detail captured in a representation of something. This could pertain to the level of detail captured in a photograph or displayed on a computer monitor. It could even relate to video frames and time code: 30 frames per second is more resolution than 24 frames per second. We most commonly speak about resolution in terms of digital audio and how much resolution a digital audio system has. In digital audio resolution is affected by the sampling rate and the bit depth of the recording: 24-bit audio is higher resolution that 16-bit audio, and a 48 kHz sample rate is more resolution that a 44.1 kHz sample rate.

Resonant

Resonance is the tendency of a mechanical or electrical system to vibrate or oscillate at a certain frequency when excited by an external source, and to keep oscillating after the source is removed. If something tends to have resonance it is said to be resonant. Resonate is the verb form - to resonate. A bell is a good example of a mechanical resonator. When exited into vibration by being struck a bell will oscillate at its many resonant frequencies and thus produce its unique sound. All mechanical structures have some resonance at some frequencies. Resonance is a particular concern with loudspeaker manufacturers because speakers, speaker enclosures, and the listening areas they are ultimately placed in all have resonances that can cause inaccuracies in sound reproduction. An example of electrical resonance would be the oscillator in a synthesizer that is used to produce sound. A good example of both electrical and mechanical resonance is feedback in a PA system.

Reverb

The remainder of sound that exists in a room after the source of the sound has stopped is called reverberation, sometimes mistakenly called echo (which is an entirely different sounding phenomenon). We've all heard it when doing something like clapping our hands (or bouncing a basketball) in a large enclosed space (like a gym). All rooms have some reverberation, even though we may not always notice it as such. The characteristics of the reverberation are a big part of the subjective quality of the sound of any room in which we are located.

Our brains learn to derive a great deal of information about our surroundings from the sound of a room and it's reverberation. Consequently it is necessary to have the proper type and amount of reverberation on recordings in order for them to be aesthetically pleasing or to sound natural to us. This can be accomplished with careful microphone placement, but it is often necessary to employ artificially created reverb.

To create reverb, a device known as a reverb unit is employed. Reverb units have historically come in many shapes and sizes, and have used many different techniques to create the reverberation. These days most of the reverb units employed throughout the world are digital, where the sound of the reverb is generated by a computer algorithm and mixed with the original signal. We will be discussing other types of reverb units in the future.

ReWire

An inter-application communication engine developed by Steinberg that allows MIDI and audio applications to interact and cooperate with one another. For example, the audio output of an application may be routed to the audio engine of another and output with the second application's audio. Further, they may communicate with each other via MIDI so that one can control the other or so they can be synchronized.

RFI

Abbreviation for Radio Frequency Interference. RFI is a specific type of EMI relating only to signals produced by radio and television systems. These hi frequency RF signals can find their way into our audio equipment where they can produce hums, buzzes, and occasionally even reproduce the actual audio of the radio station through the equipment. Most audio circuits are not designed to deal with RF frequencies, which is what turns them into problems, so the normal course of action is usually to prevent them from entering in the first place. This is typically accomplished by shielding, filtering, and proper grounding among other things.

RIAA

Abbreviation for the Recording Industry Association of America. Founded in 1952, the RIAA primarily exists to be an advocate for recording artists and record companies. They are perhaps most known for the cool gold, and platinum awards given to groups for record sales, but they are also very involved in anti-piracy issues as well as other standards and concerns of the recording industry. For example, they established the technical standards for LP records. The RIAA equalization curve is still used today in phono pre amps for playing back records. They are also largely responsible for the SCMS copy protection we've had to contend with in DAT machines.

Ribbon Cable

A type of cable, usually comprised of many smaller wires, that is in a flat configuration. Ribbon cables are made to be flat so they can more easily be routed around the insides of confined equipment and because they are easier (read cheaper) to make. Because they are flat it is easy to clamp a connector on anywhere in a length of the wire, which means a given length of wire can have many connectors. Very handy in some devices. Ribbon cables are generally not able to be shielded, and do not have protective jackets around them, so they are rarely used outside of equipment.

Ring Modulator

A type of audio mixer combining two audio signals, and outputting their sum and difference. The frequencies found in the original signals are not passed through to the output. For example, if two sine waves (single frequency waveforms containing no overtones) are inputted, one with a frequency of 1000 Hz, and the second at 400 Hz, the ring modulator will output two frequencies: 600 Hz and 1400 Hz. With more complex waveforms (which contain many more overtone frequencies) ring modulators produce a clangorous, "metallic" result often used for special effects, in synth programming, and so on. One popular use has been to process vocals, which produces sci-fi sounding "robotic" voices.

RMS (Root Mean Square)

The square root of the mean of the square. RMS is (to engineers anyway) a meaningful way of calculating the average of values over a period of time. With audio, the signal value (amplitude) is squared, averaged over a period of time, then the square root of the result is calculated. The result is a value, that when squared, is related (proportional) to the effective power of the signal.

Unfortunately, calculating the RMS value of anything but a simple sine wave (.707 of peak) is very difficult. The further a signal gets in harmonic content from a sine wave, the less accurate RMS values will be. For a dynamic signal like most music, it is nearly impossible to get even close to a true RMS value.

Note: RMS Power is actually a misnomer, since the RMS of a signal is a really just a value used to calculate average, or continuous, power.

RT60

An abbreviation for Reverb Time -60dB. It is an expression used to more specifically state what a given reverb (see WFTD archive Reverb) time is. The reverberation decay time in a large empty concert hall may be as much as 15 to 20 seconds. This means that in practice it takes that long for the reverberations of a sound to decay into the ambient noise of the hall (which includes thousands of ongoing reverberations). Raise the ambient noise level in the hall by 20 dB (perhaps by turning on a heating system) and the reverb time will sound shorter because as it decays it gets lost in the sound of the heating system. The purpose of the RT60 specification is to provide an objective measure of reverb time. The spec says that reverb time is defined as the time it takes the reverb to go down in volume by 60 dB, or to 1 millionth of the original volume.