Glossary – R
Rack (or Equipment Rack) – A cabinet or framework with rails, used to mount and house various components of outboard gear.
Rack Ears/Rack Flanges – Mounting brackets that can are attached to equipment so it can be mounted in a standard equipment rack.
Rack-Mounted – Describing outboard gear that can be housed in an equipment rack.
Radiation – The angle and pattern of coverage of a speaker.
Radiation Pattern – A graphic depiction of speaker coverage. This is not unlike the polar pattern of a microphone, with the exception that a polar pattern describes the area where sound arrives at the microphone, while a radiation pattern describes how sound is dispersed from the loudspeaker.
Ramp Wave – See “Sawtooth Wave.”
Random Access Memory (RAM) – The “short-term” memory in a computer that is used in tandem with the processor for performing immediate tasks (as opposed to hard-drive storage memory where projects are saved and recalled). In the recording studios, the more RAM a computer has, the more ability it has to handle large amounts of data at a time (for example, in multi-track recording or working with virtual MIDI instruments).
Random Note Generator – A device that generates random pitches at a set rate, used in synthesizers.
Rap – To perform a spoken rhythmic part to a music or percussion performance.
Rarefaction – The reduced density of air particles during the trough of a sound wave; in the context of “compression and rarefaction,” it is the opposite of compression. (See also “Compression.”)
Rated Load Impedance – The input impedance, or opposition to current flow by an input of a device, that a piece of equipment is designed to feed.
RCA Plug (jack) – (Also called Phono Plug) A common audio connector found on most stereo systems with a center pin as one connection and an outer shell as the second connection.
Read – To retrieve information bits from a storage device; in digital audio, the reproduction of digital signals.
Read Only Memory (ROM) – A type of data storage that cannot be erased or reprogrammed by the user. The most common form of ROM in audio/video settings today is optical storage media (i.e, CD, DVD, CD-ROM and DVD-ROM).
Reason – Popular music software program from Propellerhead Software. It offers the digital equivalent of hardware synthesizers, samplers, signal processors, sequencers and mixers. Reason works as a virtual music studio, or as a set of virtual musical instruments which can be played live or used with other sequencing software.
Record Head – A device on an analog tape machine that changes electrical current to magnetic energy; the changes of the magnetism match the waveshape of the audio signal fed to the head.
Record Level – A control on a tape machine that determines the amount of magnetic flux recorded on the tape, or the DAW control that determines the level of the digital signal recorded to the sound file.
Record Monitor – On some tape machines, a switch position that allows the VU meter and sound output of the tape machine electronics to monitor the input signal to the tape machine.
Record Ready – A control state of a multitrack tape recorder where the designated track will begin recording when the record function of the tape recorder is activated.
Recording Bus – A bus that sends a mix signals from the console channels to the multitrack recorder or DAW. (See also “Bus.”)
Recording Session – A bloc of time in which music is being recorded in the studio.
Reel – 1) The hub and flanges onto which analog tape is spooled; recording and playback involves unspooling the tape from one reel and onto another. 2) Sometimes also called “demo reel,” a compilation of audio or video that demonstrates the abilities of a musician, audio engineer, actor, or other audio/visual professional. Unlike a demo, which is intended to pitch one or more songs, a reel is a demo intended to promote the abilities of the professional rather than the product itself. The term itself is a holdover from the days when this promotional material was delivered on reels.
Reference Level – 1) A standard baseline level of volume used to measure how much level is present in dB above or below the baseline. 2) See “Operating Level.”
Reference Tone – A single-frequency tone (often at 1000 kHz) used to calibrate the levels of sound equipment; the tone used to set reference level. (See also “Test Tones.”)
Reflected Sound – Sound that reaches a microphone or listener after one or more reflections from surrounding surfaces.
Reflection – In acoustics, the bouncing of sound waves off of a flat surface, as opposed to absorption. Reflection can have a great impact on how we perceive the collective sound; reflected sounds from a distance is perceived as echo, while reverberation is created from thousands of reflections. (See also “Absorption,” “Early Reflection,” “Echo,” “Reverberation.”)
Regulated Power Supply – A device to supply power to electronic equipment whose output voltage will not fluctuate when more equipment is turned on, or if there is a change in voltage of the power line. A regulated power supply is designed to protect sensitive electronics from destructive power surges.
Relay – An electromagnetically activated switch that connects or disconnects two terminals when a control voltage is applied.
Release – The final stage in the four stages of a sound (Attack, Decay, Sustain and Release, or ADSR); the release of the sound describes the rate at which the volume drops to zero as the sound stops playing. In synthesizers, describes the volume reduction of the sound once the key is released.
Release Time – In dynamics signal processors, the time it takes for the output signal to return to original levels when the input signal crosses the designated threshold.
Remote – 1) A device that controls the functions of another device wirelessly. 2) Describing on-site recording, as opposed to recording in the studio.
Residual Magnetization – The amount of magnetism left in a magnetic material after the magnetizing force is removed. Residual magnetism can accumulate in tape machines over time, either creating distortions and noise in the sound output or partially erasing the tape.
Residual Noise – The noise level left on recording tape after it has been erased.
Resistance – The opposition of a substance to the flow of electrical current, measured in ohms.
Resistor – An electrical component with a specific amount of resistance to electrical current, used within the circuit to regulate the flow of current.
Resonance – 1) The natural tendency of physical substances to vibrate with more energy at certain frequencies. The principle of resonance is a key element in the design of acoustic instruments; for example, the hollow chamber of a guitar or violin is designed to resonate with the vibrations of the string. Resonance also plays a role the acoustic design of a space, and even in developing good vocal technique to project the voice.
Resonant Frequency – A frequency at which a physical item vibrates naturally.
Resonate – To vibrate at the resonant frequency. Also refers to the lingering reverberation that causes a sound to continue after the sound source has stopped. This continuing sound is due to the sympathetic resonance of nearby objects.
Return – See “Auxiliary Return.”
Reverb – 1) Short for “Reverberation.” (See “Reverberation.”) 2) A signal processor or plug-in that creates artificial reverb to a signal.
Reverb Time (RT) – The time it takes for the reverberation or echoes of a sound source to die out after the direct sound has stopped. Specifically, the reverb time is measured between the point at which the sound source stops and the point at which the reverberation levels fall by 60 dB.
Reverberant Field – Describes the space that is far enough from the sound source that the reverberations are louder than the direct sound.
Reverberation – The persistence of a sound after the source stops emitting it, caused by many discrete echoes arriving at the ear so closely spaced in time that the ear cannot separate them.
Reverberation Chamber – A device built to simulate room reflections.
Reverberation Envelope – The attack, decay, sustain and release of the reverberation volume; or how fast the reverberation reaches peak level and its rate of decay.
RF Signals (or RF) – Short for Radio Frequency Signals, electromagnetic waves that carry wireless radio and television signals. The vast majority of RF signals exist at frequencies higher than 100 kHz.
RF Interference – The unwanted noise introduced into electronics, circuits and/or audio systems by the presence of RF signals. RF interference in a system can result in humming, buzzing, static or even the reproduction of radio transmissions.
Rhythm Section – The musical instruments in a band or ensemble that are responsible for playing rhythmic parts rather than melody parts. In contemporary music, rhythm sections typically consist of drums and bass, along with some combination of percussion, piano/keyboard and/or guitars.
Rhythm Track(s) – The recording of the rhythm instruments in a music production.
Ribbon Microphone – A microphone that converts sound waves to electrical current via a thin conductive ribbon set between magnetic poles. Ribbon microphones are almost always responsive to sound on both sides of the ribbon, creating a bi-directional or figure-8 pattern.
Riff – A short melody repeatedly played in a tune often with variation between vocal lines.
“Ringing Out a Room” – The process of identifying and compensating for problem frequencies within a room for the purpose of optimizing live audio within that space. This is typically done by sending pink noise through the speakers, turning up the microphones to the point of feedback, and using EQ to notch out the offending frequencies.
Rise Time – The rate at which an audio waveform makes a sudden increase to a higher amplitude.
RMS Meter – A meter that recognizes and responds to the effective average, the RMS level, or the effective average value of an AC waveform, rather than to the peak level. (See also “Root-Mean-Square,” “Peak Meter.”)
Roll-Off –The reduction of signal level as the frequency of the signal moves away from the cut-off frequency, especially when the cut-off rate is mild.
Room Equalization – In live audio, an equalizer inserted in the monitor system that attempts to compensate for frequency response changes caused by room acoustics.
Room Sound – The natural ambience of a room, including the reverberation and background noise.
Room Tone – The natural background noise occurring in a room without music playing or people speaking. In recording audio for film and TV, on-set sound mixers capture a take of room tone for the purpose of providing continuity between clips of dialogue during post-production.
Root Mean Square (RMS) – The effective average value of an AC waveform. Used as a measure of the overall level of the sound rather than just measuring by the peaks. (See also “RMS Metering,” “Peak Metering.”)
Rotating Head – A circular head with two (or more) gaps that rotates against the direction of tape motion at a slight angle to the tape travel.
Rumble – A low-frequency noise, typically caused by earth/floor vibration or by uneven surfaces in the drive mechanism of a tape recorder or playback unit.