Knowledgebase

Balanced lines are typically – and quite incorrectly – explained as follows. A signal is split into two equal but antiphase parts in a balanced line driver. These signals are connected to each leg of a pair cable and eventually arrive at a balanced receiver. This device inverts one leg of the signal. In doing…

Ohms are a measure of the resistance to a flow of current. The name derives from the German physicist Georg Simon Ohm (1759-1854). The symbol for the ohm is the Greek capital letter omega. If the Greek letter cannot be used, the word ohm is used instead. In a simple circuit the relationship between the…

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

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…

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…

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…

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…

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…

An acronym for Root Mean Square, a mathematical means of calculating the average level of a varying audio signal for the purposes of metering or estimating the power of, for example, loudspeaker amplifiers.

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…

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.

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…

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…

Tesa Tape is a generic term applied to self adhesive foam rubber tapes or sheets a few mm thick. TESA is an American adhesive tape maker, with a UK subsidiary. Tesa Tape is commonly used stuck to the heels and soles of shoes to deaden the noise of footfalls on hard or hollow floors. It…

A Wild Track is an audio recording made on location with no reference to picture, intended to provide post production with useful background sound during editing. Recording wild tracks on documentary shoots it’s advisable not to switch the camera to bars, but to have the microphone in shot. With a fast turnaround in the edit,…

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…

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…

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…

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…

Super Audio CD (SACD) launched by Sony in 1999 and intended to supersede the original Sony/Philips CD.

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…

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…

Background Noise are sounds that are not the main sound you want to record. Sounds from traffic outside, air conditioning, lighting and so on. Ideally sources of background noise are stopped, switched off or removed but what do you do if you had no choice but record the noise? Record an atmos/room tone Wild Track…

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…

While it is possible to connect to Aircraft Intercom systems, the quality is at communications level rather than broadcast, though it may be adequate for short items and can give a useful “atmos”. Aside from the issues of obtaining the correct connector you MUST obtain permission from the pilot on each occasion before connecting location…

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…

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…

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.

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…

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…

AFL may be After-Fader Listen or After-Fader Level, depending on whether the user is more concerned with the quality and/or content of the signal or with its level. It is similar in operation to Pre-Fader Listen (PFL) except that the signal is derived after the channel fader instead of before. As AFL is also derived…

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…

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…

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…

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.…

Q: What is intermodulation? What causes intermods? A: Intermodulation generally only comes up in conversation when discussing interference. To understand about intermodulation products, or intermods, you need to know a little bit about transmitter and receiver design. Transmitters and receivers are designed to work at a particular frequency. High frequencies, such as those used in…

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…

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…

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 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…

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…

Lockit is a device manufactured by Ambient Recording which enables video cameras to be synchronised with audio recorders.

Direct Current or DC refers to the unidirectional flow of electrons from high to low potential, as opposed to Alternating Current or AC where the flow regularly reverses in direction at a specific frequency. By convention this flow is considered to be from positive to relatively negative points; note that this direction is not the…

An ATA Carnet is a multi-part document which is used to confirm an inventory of items which are taken out of the EU and returned within a pre-determined time. This is to prove that they have not been exported, or indeed imported when you return. Failure to complete all sections properly at any point when…

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…

The Electromagnetic Spectrum is the range of all possible frequencies of electromagnetic radiation. See the excellent diagram reproduced by kind permission of Louis Keiner http://www.keiner.us/. The sections of particular interest to IPS members are usually referred to as the Radio Spectrum (although they are mostly used for television!), and are: Low Frequency (LF) covers frequencies…

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…

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.

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…