Knowledgebase

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…

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.

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…

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…

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…

Phantom Power is a means of powering condenser microphones remotely, using balanced microphone cable. The AES (and IEC 61938) endorses two voltage levels, 48 V and 12 V, and they are referred to as P48 and P12

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…

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…

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…

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 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…

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…

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…

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…

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…

“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…

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.

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…

The human ear does not react to changes in sound in a simple, linear way. To double the loudness of a sound, say by turning up the volume control on an audio amplifier, most people find that they need to increase the power produced by the loudspeaker by about ten times. If we were to…

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…

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…

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/

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…

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…

Amps (Amperes) measure the flow of current that a potential difference forces through a circuit. The symbol is always A. The name derives from the French physicist André-Marie Ampère (1775-1836). As with Volts, current can be unidirectional – Direct Current (DC) – or alternating in direction (AC), and the values used can be peak or…

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…

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…

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…

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…

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…

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…

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…

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…

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…

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…

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…

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…

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…

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.…

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,…

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.

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.

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…

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 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.

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…

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