Knowledgebase

Metadata is literally data about data. In its simplest form it could be a note attached to an item of recording medium (e.g. a tape or disc) telling the user what is on the medium, how long it is and where and when it was recorded. More practically it will be digital information embedded in…

Alternating Current or AC refers to a flow of electrons that reverses in direction in a cyclical manner

Boom is defined in the Concise Oxford English Dictionary as “a movable arm carrying a microphone or film camera” and in Collins Concise as “a pole carrying an overhead microphone and projected over a film or television set“. In sound studios a boom is either an arm fixed to a floor-mounted microphone stand or a…

The iXML specification is designed to provide an unambiguous communication of file and project based metadata between various stages of workflow in production, telecine, picture editorial and audio post production. iXML is primarily designed to be used as a  RIFF (embedded tagged data) chunk inside a Broadcast Wave file (although it can be optionally included…

“Off Tube” is when commentary for an event is provided by the commentary team just watching the televised pictures. While commentators almost always have a picture monitor (or “tube”) regardless of their location, there is great advantage to be had from also being in a position to see the proceedings with their own eyes, and…

A Cross Point is a notional intersection between an input and an output in a Matrix, which may be represented graphically by a cross-hatch of horizontal and vertical lines. Usually the horizontal lines represent the inputs and the vertical lines the outputs, and a cross overlaid at an intersection indicates a connection – a “cross…

Volts (symbol V – not v) measure the electrical pressure, or potential difference available to force current through a circuit. The name derives from the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile, the first chemical battery. Voltages can have a fixed polarity (Direct Current volts), or can change more or less cyclically…

Running a business, owed money from another business? Then you have a statutory right to interest and compensation under the Late Payment of Commercial Debts (Interest) Act 1998 (as amended). There is no obligation to charge interest or claim compensation on a late payment, you just have a legal right to do so. Be aware…

A “Cue” may be visual or aural. In television it is usual for somebody in the studio to be given a visual cue to begin by a wave from the Floor Manager, and also sometimes to conclude by “winding up” gestures (which become more frantic as time runs out!). In radio a cue light is…

Problems are usually bus and/or buffer overload. As Macs and PCs now share the same Intel chipsets, hopefully the “rules” that you have to apply to optimise a PC for audio will be similar. Basically the machine needs to be focussed entirely on handling audio and minimising system interrupts on its data buses. While the…

For large items where ordinary postal services may be too expensive, members have had success using the following providers. Most are reselling the services of other major courier/delivery firms and collect from your premises. Parcel 2 Go Appear to offer a choice of carrier at various price points depending mainly on how quickly you want…

This page lists the most common digital interface standards used to connect between digital mixers, recorders, editing systems and microphones etc. Contents ADAT AES/EBU SPDIF SDIF TDIF-1 Mitsubishi ProDigi MADI Yamaha ADAT ADAT is an acronym for Alesis Digital Audio Tape, a format for recording 8 tracks of digital audio onto Super VHS magnetic tape.…

Electrical impedance is effectively resistance in an AC circuit (see Ohms). Impedances are significantly more complicated than simple resistance because they are frequency conscious and because they can apply to the behaviour of an entire circuit rather than a single element. There are load impedances, having the effect of a virtual resistor across the input…

Timecode in audio operations refers to the SMPTE/EBU time and control code which is used for synchronising audio with video and for locating sections of programmes. Linear Time Code (LTC) is most commonly used, although Vertical Interval Timecode (VITC) may be encountered in television operations. Both versions use an 80-bit binary code to identify video…

The Polar Pattern of a Microphone describes its directional sensitivity. The main family of patterns is a continuous spectrum between omni and bi-directional (figure-of-eight). Thus their titles are somewhat arbitrary, often overlap and, perversely, in most cases they are best defined by their ability to reject sound. Polar Patterns are generalised – they give an…

Microphones work by sensing minute changes in air pressure. Pressure A pressure operated microphone is essentially a sensitive barometer and reacts only to changes in pressure irrespective of the direction of the sound source. It comprises a sealed box with air inside and a thin diaphragm that deflects for small pressure changes. Some form of…

First of all to quash a big misnomer. A Diary Service is not there in order to ‘get you work’. That is what an Agent does. Now – to more detailed thoughts. When looking at Diary Services it might be wise to take a brief look at how they emerged and why. In the late…

Automated Dialog Replacement (ADR) was used by the Magnatech Corp as a marketing phrase (mid 1960s). Magnatech made the system which comprised the projector, the recorder and the control box. It enabled record drop-ins and -outs across 3 tracks (3 attempts) to be programmed to the footage counter, and the whole reel of 10 minutes…

An Induction Loop or Audio Frequency Induction Loop System (AFILS) is a system commonly used by hearing aid users to clearly hear the sound in a theatre, through the bandit-proof glass screens in a bank or just a telephone call. It can also be used to provide wireless talkback or IEM to crew or presenters…

Stereo, short for Stereophonic, is a system of sound recording and reproduction which uses two synchronised channels, usually referred to as A (left) and B (right). There are several conventions for colour-coding analogue signals; the BBC adopted the nautical convention of Red for Port (Left) and Green for Starboard (Right), which can be confusing when…

Electret personal microphones are all unbalanced. They all need a screen, both for the cable and for the grille and casing around the capsule. This usually gets connected to 0V. The electronics inside the capsule will have two external connections. One connection always needs to be kept more +ve than the other but it makes…

Analogue audio signal levels have historically been categorised for professional usage in two groups – microphone level (low) and line level (high). Domestic equipment generally falls into a third category, just below professional line level. Signal levels are measured using units based on the Decibel. There are many different types of Level Meter used for…

Broadcast Wave Format was developed by an EBU Project Group (see The Broadcast Wave Format – an Introduction) to provide a product-independent means of exchanging programme material between workstations from different manufacturers. It is based on the Microsoft WAVE audio file format (file extension .wav), which is one of a number of file types specified…

The European Broadcasting Union or EBU was formed on 12 February 1950 by 23 broadcasting organisations from Europe and the Mediterranean. Members are radio and television companies, most of which are government-owned public service broadcasters or privately owned stations with public missions. In 2007 the EBU has 74 active members from 55 countries, and 43…

Earthing for Audio The following is taken from an article published in the Nov/Dec 2005 issue of LineUp by Peter Thomas, Managing Director of the Professional Monitor Company, with his kind permission. At the outset, I need to make clear that there are no references to PMC loudspeakers at all (except in this introduction). Neither…

Direct Stream Digital (DSD) uses a sampling rate of 2.8224 MHz to directly record a 1-bit signal. Used for recording SACD, launched by Sony in 1999.

A Sabin is the amount of absorption equivalent to one square metre of open window (which would allow the sound to escape from the room with no reflections). Named after American acoustician Wallace Clement Sabine (June 13, 1868 – January 10, 1919).  See also Sound Absorption Coefficients for Some Common Materials.

This “Bright Eyes” device was described by Hugh Robjohns in this Line Up article (June/July 2006) and uses a circuit designed by Chris Woolf. A Bright Eyes can be a very useful tool to have during rigging or fault finding to check if an XLR cable has active microphone powering. It is simple to construct…

Mix Minus describes the arrangements used when a broadcast studio is connected to an external site such as an Outside Broadcast as a contribution or another studio which is simultaneously broadcasting the same programme in another region, two way working. In both cases the remote source needs a feed of the programme but not of…

Taken from Annex B of AES11. “AES recommended practice for digital audio engineering – Synchronization of digital audio equipment in studio operations” Annex B (Informative) Word Clock It is possible to meet all the timing requirements of AES11 by means of a square wave at sampling frequency basic rate, commonly called word clock. It is…

Black and Lane’s Ident Tones for Surround (BLITS) developed by Sky Television Sound Supervisors Martin Black and Keith Lane in 2005/6 to provide a standardised form of channel identification and alignment for surround sound material. BLITS is a broadcast-specific line up tone system for use with 5.1 surround sound formats, and is currently being considered…

Critical Distance or Dc is the distance from a sound source where the level of direct sound equals that of any reverberant sound. Dc applies to all sound gathering but measuring it is normally only required when advance planning of microphone positions is needed. Critical Distance does not dictate where a microphone must be placed…

An Interference Tube is simply a long metal tube with a series of circumferential slots cut into it, fitted onto a directional Microphone. These slots produce interference patterns in sound waves from the sides, resulting in partial cancellation of off-axis sounds and a resultant apparent increase in the gain of sounds from directly in front.

Noisy Floors can be the bane of a Sound Recordists life. There are two main problems; noise from things like heels hitting a hard and hollow floor and noise from the floor itself as objects move over the surface. Heels and Legs High heels and chair legs can easily produce enough noise to drown out…

Watts are a measure of power. The symbol is W (never w). Electrically Watts = Amps x Volts. The name derives from Scottish engineer and inventor James Watt (1736 – 1819) in honour of his work that transformed the primitive steam engine into a practical power unit. Watts are obviously useful for indicating the power…

Most mixers, except for portable types, have an associated Jackfield, also known as a Patchbay, either integral with the mixer frame or fitted nearby in a wall-mounted rack or free-standing console. The jackfield is used to terminate incoming lines from remote studios, tape machines etc and to provide access to the mixer line inputs and…

Contents 1 Sex 2 XLR 2.1 3 pin 2.2 4 pin 2.3 5 pin 2.4 6 pin 2.5 7 pin 3 Jack 3.1 ‘A’ gauge 3.2 ‘B’ gauge 3.3 MIL-plug 3.4 Bantam 3.5 3.5mm 3.6 2.5mm 4 Hirose 4.1 4 pin 4.2 10 pin 5 Tajimi 5.1 12 pin 6 DIN 6.1 2 pin 6.2…

PFL usually stands for “Pre-Fader Listen”. PFL is a combined channel and monitoring function. On an analogue mixer with PFL, each channel has a switch which can connect the channel signal path, at a point just before the fader, to the pre-fade bus. This bus is picked up in the monitor module and made available as an…

Advice/Tips on getting good sound for aircraft PTCs (Piece to Camera) The general advice here is to get your microphone as close as possible to the presenter’s mouth. A common technique is to attach your personal mic to the aviation boom but on the opposite side to the mouth as this helps shield the microphone…

Stick Pads are the soft rubber things that you fit onto the end of a walking stick to protect the end of the stick and reduce the noise of the stick hitting the ground. Sound Recordists use them on high heels or chair legs to reduce the sounds of walking or chair movements on hard…

This is a selection of computer software for audio applications which is either free or inexpensive. It has been compiled from various sources, and inclusion in this listing does not in any way imply any endorsement by the IPS, or any warranty that it will be satisfactory. User (and buyer) beware! Contents 1 PC Software…

Pressure Zone Microphone is a registered trade mark of Crown International, and describes a method of mounting a microphone close to a flat surface to minimise room acoustics. Other variants are described as Boundary Microphones. See http://www.uneeda-audio.com/pzm/

The following hints and tips have been collated from emails on IBSNET. from Florian Camerer (ORF) I used the PD-2, which is – in my opinion – more reliably built (metal housing etc.) and consumes more power, yes, more power, and that means more heat in the machine!! I conducted tests in Vienna in a…

A member asked on IBSNET for advice on hydrophones. Chris Woolf responded:- Hydrophones vary quite a bit in quality from high grade phantom powered  devices to some pretty poor plug-in power versions. The are invariably omnis and since the propagation of sound in water is very different to air you can expect a lot of LF…

Foldback is a feed of audio to the studio, via either loudspeaker, headphone or earpiece (IEM). It may be to provide the presenter and/or performers with a Cue feed from an external source or from a singer’s Microphone, to reinforce a singer’s voice for confidence or as an aid to tuning, or to provide actors…

An Edit Decision List (EDL) is simply an ordered list of items of recorded video and audio with Timecode references which enables a video editor to assemble a version of the final programme.

A Creative Commons Licence allows authors, artists, and educators to mark their creative work with the freedoms they want it to carry, changing the default of “All Rights Reserved” into “Some Rights Reserved”, as the creator chooses. There are three areas that the licence covers; attribution, commercial use and derivatives. These can be combined in…

Sound Pressure Levels Our ears respond to fluctuations in the steady atmospheric pressure, so when measuring sound, that is what we usually measure. Sound pressure levels (or Sound Levels for short) are specified in Decibels, relative to a reference pressure of 20 micropascals. This reference pressure of 20 micropascals is nominally equal to the threshold…

Tonader Power, T Power, T12 or AB Power all refer to a method of powering microphones via their cable. This system uses 180 ohm feed resistors and a 12V supply but does not send the DC power as a common mode signal like Phantom Power. The powering is unbalanced and shares the same path as…

Talkback originated in radio studios, where staff in the control cubicle who could hear the presenters and performers on their monitor loudspeaker were able to communicate with them using a dedicated microphone/loudspeaker system, “talking back” to the studio. This system was extended by the introduction of “reverse talkback” which provided the presenter with an additional…