Reference

Glossary

Sixty-two terms used across the ten pieces on this site, each defined in one or two sentences, with a link to the piece that explains it properly.

Definitions are written for a reader who has met the word and wants to know what it does, not for one preparing an examination. Where a term has two unrelated meanings in this field, both appear.

A

AES67: An Audio Engineering Society standard that lets audio over IP equipment from different manufacturers exchange streams on the same network, with clocking handled by precision time protocol. See the wiring of a room that talks back.
Automatic gain control: A slow-acting level control that brings widely different sources to a common level before anything else processes them. When it is audible it is set too fast.
AQH persons: Average quarter-hour persons: the average number of people listening during a typical quarter hour of a daypart, counting anyone who listened at least five minutes of it. The unit advertising is bought in.
Attention signal: The two tones, 853 Hz and 960 Hz, sounded together for eight to twenty-five seconds before the spoken part of an emergency alert. Using it outside a genuine alert or authorised test is prohibited.
Automation: The playout system that reads a log and puts its elements to air in order, handling segues, hard start times and switching between local and networked sources.

B

Balanced line: A connection carrying the signal twice, in opposite polarity, inside a shield, so that interference picked up along the run cancels at the receiving end. The reason professional microphone cables can be long.
Baseband: On an FM station, the single composite audio-frequency signal that actually modulates the carrier, containing the mono sum, the pilot, the stereo difference channel and any data subcarriers. Also called the composite or the multiplex.
Benchmark: A recurring programme feature at a fixed time on fixed days, used to give an audience a reason to arrive at a particular minute rather than drift in.
Blanket licence: A licence covering an organisation's entire repertoire for a single fee, usually a share of revenue, rather than title by title. The mechanism that makes music radio administratively possible.
Blend: Two unrelated meanings. In an analogue receiver, the progressive move from stereo towards mono as a signal weakens. In a hybrid digital station, the cross-fade between the analogue and digital versions of the same programme.
Booster: A low-power transmitter rebroadcasting a parent station on the same frequency, inside the parent's own protected contour, used to fill terrain shadows rather than to extend range.
Burn: The point at which a listener's familiarity with a record turns into fatigue. Detecting it is the main purpose of music research, and it is what rotation arithmetic runs against.

C

Capture effect: The tendency of an FM receiver to lock onto the stronger of two signals on the same channel and suppress the weaker almost entirely, needing only a few decibels of difference. Why FM interference is abrupt rather than muddy.
Cardioid: A microphone polar pattern most sensitive at the front and deafest directly behind. Its narrower relatives, supercardioid and hypercardioid, are deafest to the sides of the rear rather than straight back.
Clear channel: A medium-wave channel on which one or more stations receive wide protection, including against night-time sky-wave interference, so that their signal remains usable at very long distances after dark.
Contour: A line on a coverage map joining points of equal predicted field strength. It is calculated from statistical propagation curves, not measured, and it says nothing about what any individual receiver will do.
Cume: The number of different people who listened to a station at least once, for at least five minutes, in a reported period. Reach, as opposed to the average quarter-hour figure, which is reach multiplied by duration.

D

Daypart: A named block of the broadcast day, conventionally morning drive, middays, afternoon drive, evenings and overnight. The blocks differ enormously in audience and therefore in investment.
dBTP: Decibels relative to full scale, measured as true peak: an oversampled reading that catches the peaks occurring between digital samples. Delivery specifications usually cap it at -1 dBTP.
dBu, audio: A voltage level referenced to 0.775 volts. Professional equipment operates at a nominal +4 dBu; consumer equipment sits about twelve decibels lower on a different reference.
dBu, field strength: Decibels above one microvolt per metre, the unit coverage contours are drawn in. The same three letters as the audio unit, with no relationship to it whatsoever.
Deviation: How far an FM carrier's instantaneous frequency swings from its assigned centre. Full modulation in the American FM service is a peak deviation of 75 kHz. See what is actually riding on an FM carrier.
Dynamic microphone: A microphone in which a diaphragm moves a coil through a magnetic field, generating its own signal with no power supply. Rugged, comparatively insensitive, and the broadcast standard for voice.

E

Effective radiated power: Transmitter power, minus what is lost in the feedline, multiplied by the antenna's gain in a given direction. Quoted for FM relative to a half-wave dipole, and much larger than the transmitter's own output.
Emission mask: The regulatory limit on how much energy a transmitter may emit at increasing distances from its assigned frequency. Every subcarrier and digital sideband has to fit underneath it.

F

Format: A stable set of expectations about what a station will play next, maintained by rotation categories, separation rules and imaging. Not a genre and not a playlist. See a format is a promise about the next song.
Format wheel: The hour drawn as a circle divided into labelled wedges, showing where music, commercial breaks, features and the legal identification fall. Also called an hour clock.

G

Gating: In loudness measurement, the discarding of quiet blocks so that silence does not drag the result down. Without it, the same programme edited tightly and edited loosely would measure differently.
Ground wave: A medium-wave signal that follows the curvature of the earth, losing energy into the ground as it goes. It is the daytime coverage of an AM station, and its reach depends heavily on soil conductivity.

H

HAAT: Height above average terrain: the elevation of an antenna's centre of radiation compared with the average elevation of the land from three to sixteen kilometres out. The number that decides coverage, and not the same as tower height.
Hybrid: The device that separates the two directions of a telephone line so a caller can be put on air. It never separates them perfectly, which is why a mix-minus is required as well.

I

Imaging: Everything a station broadcasts about itself that is not programming: jingles, sweepers, liners and the positioning statement that names the one attribute it wants remembered.
Integrated loudness: The gated loudness of an entire programme, expressed in LUFS or LKFS. It is the figure a delivery specification is written against, and the only one worth arguing about.
In-band on-channel: A digital broadcast system whose carriers sit alongside an existing analogue signal inside the same channel allocation, so that analogue receivers are unaffected.

K

K-weighting: The filter used in loudness measurement, combining a high shelf that approximates the effect of a head in a sound field with a high-pass that de-emphasises the very low end.

L

Legal identification: The announcement a licensed station must make at the top of each hour, carrying its call sign and the community it is licensed to serve, at a natural break as close to the hour as feasible.
LKFS and LUFS: Two names for the same loudness unit, one from the ITU and ATSC world and one from the European Broadcasting Union. One unit of either equals one decibel.
Loudness range: A measure of how widely the short-term loudness of a programme varies, after statistical trimming. A narrow range survives a noisy car; a wide one rewards headphones.
Low power FM: A noncommercial service created in 2000, limited to 100 watts at 30 metres height above average terrain, giving a service radius of roughly 5.6 kilometres. Unlike a translator, it may originate its own programming.

M

Master use licence: Permission from the owner of a specific recording to use that recording. Separate from, and additional to, permission from the publisher of the underlying song.
Mix-minus: A feed sent to a remote participant containing the full programme mix minus that participant's own audio. Without it, a caller hears themselves delayed and cannot speak fluently.
Multipath: Reception of the same signal by two or more paths of different length, causing cancellation at some frequencies. In a moving vehicle it produces the fluttering sound called picket fencing.
Musical work: The composition itself, melody and lyrics, owned by songwriters and publishers. One of the two copyrights inside every recording; the other is the sound recording.

P

Pilot tone: The continuous 19 kHz tone in an FM stereo signal. It announces that stereo is present and provides the reference from which the receiver rebuilds the 38 kHz subcarrier.
Pre-emphasis: A treble boost applied before FM transmission and cancelled by a matching cut in the receiver, which removes hiss along with the boost. The time constant is 75 microseconds in North America and 50 elsewhere.
Profanity delay: A rolling buffer, commonly seven to ten seconds, that lets a producer discard material before it reaches the transmitter. It is rebuilt by stretching audio imperceptibly, and offers no protection while rebuilding.
Proximity effect: The bass lift that appears as a directional microphone approaches a source. It belongs to pressure gradient microphones only; a true omnidirectional has none of it.

R

RDS and RBDS: The low-rate data channel at 57 kHz carrying station name, programme type, radiotext and alternative frequency lists. RBDS is the North American variant of the European RDS specification.
Reconciliation: The comparison, after transmission, of what actually played against what was scheduled. It produces the affidavits sent to advertisers and identifies spots owed as make-goods.
Rotation category: The bucket a record sits in, which determines how often it plays: heavy current, recurrent, power gold and so on. The turnover of a category is how long it takes to play through.

S

Separation rule: A constraint in music scheduling forbidding the same artist, title, tempo, era or vocal type from returning too soon. Categories decide frequency; separation decides arrangement.
Sky wave: A medium-wave signal that refracts off the ionosphere and returns to earth far from the transmitter. It exists at night, when the absorbing D region has thinned, and not by day.
Sound recording: One specific captured performance, owned by whoever owns the master. In American law it has a public performance right for digital transmissions only, not for over-the-air broadcast.
Statutory licence: A licence granted by law rather than negotiated, at a rate set in a public proceeding. It covers non-interactive digital transmission of sound recordings, and comes with conditions on how often and how predictably a service may play them.
Stopset: A commercial break. The total per hour is the spot load, and it is the most direct lever a station has on both revenue and tune-out.
Studio to transmitter link: The path carrying programme audio from the studio to the transmitter site, whether a licensed radio link, a wired or IP circuit, or an off-air relay used as a fallback.
Subcarrier: A carrier riding inside the baseband of another signal, used on FM for the stereo difference channel, for station data and for subsidiary services.

T

Time spent listening: How long the average listener stays with a station in a reported period. Multiplied by reach, it produces the average quarter-hour figure.
Translator: A low-power transmitter rebroadcasting another station on a different frequency, with no programming of its own. A fill-in translator must sit inside the primary station's protected contour.
True peak: The highest value of the reconstructed waveform, including peaks that fall between digital samples. A sample peak meter cannot see them, and an encoder or converter can turn them into audible distortion.
Turnover: How long a rotation category takes to play through and begin again. Nearly every complaint that a station repeats itself is a turnover figure someone chose on purpose.

V

Voice tracking: Recording presenter links in advance, against the tail and head of the surrounding songs, for an automation system to place. Done carefully it is inaudible; done carelessly it produces yesterday's weather.