TA 20 - Analogue and digital audio

IEC 61937-16:2024 describes the method to convey non-linear PCM bitstreams encoded in accordance with the AVSA format.

IEC 60268-24:2023 is applicable to active acoustic noise-cancelling headphones and earphones which have the function of reducing the noise heard by the user by the output sound from the transducer generated by the environment noise detection microphone and the noise reduction signal processing circuit.
This document specifies the terms and definitions of this type of headphones or earphones, the characteristics to be specified, and the measurement and evaluation methods.
The noise detection microphone or microphones are mounted in the body, on the surface, or on an accessory of the headphones or earphones. Signal processing circuits are analogue and digital electronic circuits.
This document does not deal with equipment intended for hearing protection.
The noise cancelling characteristic measurement methods can be applied to headphones and earphones having no active noise cancelling function.

IEC 60268-23:2023 specifies acoustical measurement methods that apply to TV sets, monitors with built-in loudspeakers, and other audio devices having similar acoustical properties (e.g. flat-panel loudspeakers). The acoustical measurements are performed under free-field conditions and in-situ.
This document does not assess the perception and cognitive evaluation of the reproduced sound, nor the impact of perceived sound quality.

IEC 60958-3:2021 specifies the consumer application of the interface for the inter-connection of digital audio equipment defined in IEC 60958-1. IEC 60958-3:2021 cancels and replaces the third edition published in 2006, Amendment 1:2009 and Amendment 2:2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) The relevant part of IEC 60958-5 is supported.

IEC 60958-1:2021 describes a serial, uni-directional, self-clocking interface for the interconnection of digital audio equipment for consumer and professional applications. It provides the basic structure of the interface. Separate documents define items specific to particular applications. The interface is primarily intended to carry monophonic or stereophonic programmes, encoded using linear PCM and with a resolution of up to 24 bits per sample. When used for other purposes, the interface is able to carry audio data coded other than as linear PCM coded audio samples. Provision is also made to allow the interface to carry data related to computer software, multimedia technologies, or signals coded using non linear PCM. The format specification for these applications is not part of this document. The interface is intended for operation at audio sampling frequencies of 32 kHz and above. Auxiliary information is transmitted along with the programme. IEC 60958-1:2021c ancels and replaces the third edition published in 2008, and Amendment 1:2014. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) The relevant part of IEC 60958-5 is supported.

IEC 61937-11:2021 describes the method to convey non-linear PCM bitstreams encoded in accordance with the MPEG-4 AAC format and its extensions (spectral band replication, parametric stereo and MPEG surround), and non-linear PCM bitstreams encoded in accordance with the MPEG-D USAC format, framed in MPEG-4 LATM/LOAS. IEC 61937-11:2021 cancels and replaces the first edition published in 2010, and Amendment 1:2018. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) MPEG-D USAC has been added.

IEC 61937-2:2021 specifies the digital audio interface to convey non-linear PCM encoded audio bitstreams applying IEC 60958-1 and IEC 60958-3. This document specifies burst-info, which defines content information about the data contained in the burst-payload. IEC 61937-2:2021 cancels and replaces the second edition published in 2007, Amendment 1:2011 and Amendment 2:2018. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) new audio data-types of MPEG-D USAC, ACX, ACX HBR2, ACX HBR4 and ACX HBR8 have been added;
b) extended data-type field in Pe has been activated.

IEC 61937-15:2021 describes the method to convey non-linear PCM bit streams in accordance with the Auro-Cx format.

IEC 61937-1:2021 applies to the digital audio interface using the IEC 60958 series for the conveying of non-linear PCM encoded audio bitstreams.
It describes the way in which this digital interface can be used in consumer applications. The professional mode is not considered within the scope of this document.
IEC 61937-1:2021 cancels and replaces the second edition published in 2007, and amendment 1 published in 2011. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) Activation of Pe field;
b) Enhanced usage of channel status bits.
c) Addition of Annex B.
The contents of the corrigendum of March 2024 have been included in this copy.

IEC 60958-5:2021 enhances the consumer application of the interface for the interconnection of digital audio equipment defined in IEC 60958-1 and IEC 60958-3, introducing:
- multichannel;
- multi-stream;
- high-resolution;
- multimedia extension;
- related applications.

IEC 60268-16:2020 defines the STI model, test signals, measurement and prediction methods.
The objective of this document is to provide a comprehensive manual for all types of users of the STI model in the fields of audio, communications and acoustics.
This document does not provide STI criteria for certification of transmission channels (e.g. criteria for a voice-alarm system), but some typical application values are provided in Annex G.
Every measurement method has limitations, and the reader is referred to clauses relating to limitations such as speech privacy, echo and systems using digital voice compression (vocoders).
This document does not cover the case of fluctuating noise on the STI, although some general comments on dealing with this complex issue are provided in 7.13 and 8.9.3.
IEC 60268-16:2020 cancels and replaces the fourth edition published in 2011. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) the spectrum of the male speech test signal has been changed, with significant reductions in the 125 Hz and 250 Hz bands being implemented;
b) some corrections to formulae have been made;
c) additional information has been included on prediction and measurement procedures;
d) spectrum and weighting factors for female speech have been removed;
e) verification information for STI measurement devices added;
f) the relationships between STI and number of other speech intelligibility measures have been updated in Annex E;
g) greater information is given in Annex M about adjustments to the measured STI results to simulate effects of alternative ambient noise and speech levels.

IEC 60268-22:2020 applies to transducers converting an electrical input signal into a mechanical or acoustical output signal. However, if the electrical input terminals and the surface of the radiator are accessible, this document can also apply to passive and active sound systems such as loudspeakers, headphones, TV-sets, multi-media devices, personal portable audio devices, automotive sound systems and professional equipment. This document describes only electrical and mechanical measurements that help assess the transfer behaviour of the device under test (DUT). This includes operating the DUT in both the small- and large-signal domains. The influence of the target application's acoustical boundary conditions (e.g. car interior) can also be considered in the physical evaluation of the sound system. Perception and cognitive evaluations of the reproduced sound and the impact of perceived sound quality are outside the scope of this document.

IEC 60268-7:2010, is applicable to headphones, headsets, earphones and earsets, intended to be used on, or in, the human ear. It also applies to equipment, such as pre-amplifiers, passive networks and power supplies which form an integral part of the headphone system. It specifies the characteristics which should be included by the manufacturer in specifications, and relevant methods of measurement. It includes a classification of the different types of earphone, mainly characterized by the way in which the transducer is coupled acoustically to the ear, and a classification code which may also be used for marking. cancels and replaces the second edition published in 1996, and constitutes a technical revision. This edition contains the following changes:
- clause/subclause renumbering in accordance with ISO/IEC Directives, Part 2;
- addition of a measurement system using HATS;
- addition of details on pinna simulators for high measurement reproducibility, see Annex A. The contents of the corrigendum of November 2012 have been included in this copy.

IEC 63034:2020 specifies the characteristics of microspeakers as well as the relevant test methods on microspeakers using steady-state sinusoidal signals, sinusoidal chirp, multi-tone or noise. The main characteristics include, but are not limited to, impedance, displacement, amplitude frequency response, distortion, and power handling.

IEC 62574:2020 specifies the general channel assignment and the metadata for multichannel audio format. This document, with its channel mapping and labelling content, provides the unified usage of channel assignments for source devices, digital audio interfaces and sink devices. The general channel assignment excludes the specification of the exact position of each loudspeaker. The metadata has the exact position of each loudspeaker; however, since the position of the loudspeaker is different in various surround sound formats, the position information of the metadata is not standardized. It is aimed at consumer applications; it is not targeted at theatrical environments. Up to 65 labels for loudspeaker positions and 15 labels for loudspeakers on the display are specified, which can be used for all current multichannel audio formats. The channel assignment concept is room centric and listener centric. This general channel assignment specifies the position of the loudspeaker as seen from the listener.
IEC 62574:2020 cancels and replaces the first edition published in 2011. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) model of channel assignment spaces is changed;
b) definition of channel maps and labels is changed;
c) metadata is newly specified;
d) channel maps and labels from the first edition are included in Annex A.

IEC 60098:2020 applies to analogue audio disk records and the corresponding professional and domestic reproducing equipment. It excludes amplifiers and loudspeakers, methods of measurement for which can be found in IEC 60268-3, IEC 60268-5, IEC 60268­21 and IEC 60268-22.
IEC 60098:2020 specifies the characteristics that are necessary to ensure compatibility between analogue audio disk records and the corresponding reproducing equipment.
It also lists and defines the most important characteristics affecting the performance of reproducing equipment, and establishes agreed methods of measurement for these characteristics.
IEC 60098:2020 cancels and replaces the third edition published in 1987. This edition constitutes a full revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) addition of a tolerance on groove width.

IEC 62760:2016 specifies the audio reproduction method for normalized loudness level of audio sources for consumer equipment and systems.

IEC 60268-21:2018 specifies an acoustical measurement method that applies to electro-acoustical transducers and passive and active sound systems, such as loudspeakers, TV-sets, multi-media devices, personal portable audio devices, automotive sound systems and professional equipment. The device under test (DUT) can be comprised of electrical components performing analogue and digital signal processing prior to the passive actuators performing a transduction of the electrical input into an acoustical output signal. This document describes only physical measurements that assess the transfer behaviour of the DUT between an arbitrary analogue or digital input signal and the acoustical output at any point in the near and far field of the system. This includes operating the DUT in both the small and large signal domains. The influence of the acoustical boundary conditions of the target application (e.g. car interior) can also be considered in the physical evaluation of the sound system. This document does not assess the perception and cognitive evaluation of the reproduced sound and the impact of perceived sound quality.

IEC TS 62312-2:2018 gives guidelines for methods of synchronization of audio and video. It describes the system model and general methods for the synchronization of audio and video. The methods exclude the synchronization of the signal source and the spatial delay of audio reproduction. IEC TS 62312-2:2018 cancels and replaces the first edition published in 2007. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) fingerprint is newly introduced;
b) addition of the synchronization information from fingerprint (SMPTE spec.);
c) addition of the method for using the above information.

IEC TS 62312-1-1:2018 gives guidelines for methods of synchronization of audio and video and describes general measurement methods for the synchronization of audio and video equipment. IEC TS 62312-1-1:2018 cancels and replaces the first edition published in 2008. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) new Annex B informs of general measurement and test method of audio latency;
b) comments from SMPTE (including small technical issues).

IEC 60268-4:2018 specifies methods of measurement for the electrical impedance, sensitivity, directional response pattern, dynamic range and external influences of sound system microphones, and also details the characteristics to be specified by the manufacturer. It applies to sound system microphones for all applications for speech and music. It does not apply to measurement microphones, but it does apply to each audio channel of microphones having more than one channel, for example for stereo or similar use. It is also applicable to flush-mounted microphones and to the analogue characteristics of microphones with digital audio output. For the purposes of this International Standard, a microphone includes all such devices as transformers, pre-amplifiers, or other elements that form an integral part of the microphone, up to the output terminals specified by the manufacturer. The major characteristics of a microphone are considered in Clauses 6 to 21. Additional characteristics are considered in Annex A and Annex C. IEC 60268-4:2018 cancels and replaces the fifth edition published in 2014. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) subclause 19.4 on "pop" measurement replaces Annex C;
b) new Annex D for noise measurements in the digital domain.

IEC 60268-3:2018 applies to analogue amplifiers, and the analogue parts of analogue/digital amplifiers, which form part of a sound system for professional or household applications. It specifies the characteristics that should be included in specifications of amplifiers and the corresponding methods of measurement. This part of IEC 60268 shall be used in conjunction with IEC 60268-1:1985 and IEC 60268 2:1987. This fifth edition cancels and replaces the fourth edition published in 2013. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) rated condition of digital input is newly specified;
b) tolerance of rated power supply is changed;
c) maximum effective output power is appended to output characteristics list;
d) "Terms, definitions and rated values" clause is complemented.

IEC 61937-13:2018(E) specifies the method to convey non-linear PCM bitstreams encoded according to the MPEG‑H 3D Audio format.

Specifies the functions and performance characteristics of measuring assemblies and the methods of test to be used to determine compliance with the requirements of this standard.

IEC 61938:2018 gives guidance on current practice for the characteristics of multimedia analogue interfaces to achieve interoperability between equipment from different manufacturers. It is not a performance standard. Recommendations for interfaces for equipment used in vehicles, and for analogue video interfaces for broadcast and similar equipment, are not given. Refer to IEC 60958 for the interconnection of digital signals. This third edition cancels and replaces the second edition published in 2013. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) electric tolerance is standardized;
b) recommended value of output source impedance is adjusted;
c) value of 6 Ohms is additionally recommended to impedance-defined loudspeaker systems;
d) values in each table are chosen with respect to the state of the art and representative of best practice in industry.

IEC 61937-9:2017(E) describes the method to convey non-linear PCM bitstreams encoded according to the MAT format.
This second edition cancels and replaces the first edition published in 2007. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition: addition of new frame rates.

IEC 61937-10:2017(E) specifies the method for IEC 60958 to convey non-linear PCM bitstreams encoded in accordance with the MPEG-4 audio lossless coding (ALS) format.
This second edition cancels and replaces the first edition published in 2011. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) Addition of Levels 2, 3, 4 of MPEG-4 ALS Simple Profile;
b) Addition of data-type bits 0-4 and data-type bits 5-6 for MPEG-4 ALS with LATM/LOAS header.

IEC 61937-3:2017 describes the method used to convey non-linear PCM bitstreams encoded according to the AC-3 and enhanced AC-3 formats. This third edition of IEC 61937-3 cancels and replaces the second edition published in 2007. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) removal of support for enhanced AC-3 bitstreams with a sampling frequency of 32 kHz;
b) updates to normative and informative references;
c) clarification of pause data-burst usage for enhanced AC-3 bitstreams.

IEC 63035:2017 specifies a hardware and software specification which makes it possible to exchange symbolic music and control information between different musical instruments or other devices such as sequencers, computers, lighting controllers, mixers, etc. using MIDI technology (musical instrument digital interface):

IEC 62777:2016 determines of the performance of directional loudspeaker array systems, compares these system types, and determines their proper practical application, by listing the characteristics which are useful for their specification. It specifies uniform measurement methods for these characteristics.

IEC 60268-4:2014 specifies methods of measurement for the electrical impedance, sensitivity, directional response pattern, dynamic range and external influences of sound system microphones, and also details the characteristics to be specified by the manufacturer. This fifth edition cancels and replaces the fourth edition published in 2010, and constitutes a technical revision. It includes the following changes:
- clarification of Table 5 of classification of characteristics;
- clarification of graphical representation;
- clarification of environmental influences;
- rewritten clause for EMC;
- tolerances and more specific values for noise measurements;
- inclusion of near-field response for sound source-to-microphone distances of the order of 30 cm.

IEC 60268-16:2011 specifies objective methods for rating the transmission quality of speech with respect to intelligibility. It provides a comprehensive manual for all types of users of the STI method in the fields of audio, communications and acoustics. Three methods are presented, which are closely related and are referred to as STI, STIPA, and STITEL. The first two methods are intended for rating speech transmission performance with or without sound systems. The STITEL method has more restricted uses. This fourth edition cancels and replaces the third edition, published in 2003, and constitutes a technical revision. It includes the following significant technical changes with respect to the previous edition:
- development of more comprehensive, complete and unambiguous standardization of the STI methodology;
- the term STIr is discontinued. A new function for the prediction of auditory masking effects is introduced;
- the concept of 'speech level' and the setting of the level of the test signal have been introduced;
- additional information has been included on prediction and measurement procedures. The French version of this standard has not been voted upon.

IEC 62459:2010 applies to the suspension parts of electroacoustic transducers (for example, loudspeakers). It defines the parameters and measurement method to determine the properties of suspension parts like spiders, surrounds, diaphragms or cones before being assembled in the transducer. The measurement results are needed for engineering design purposes and for quality control. Furthermore, this method is intended to improve the correlation of measurements between suspension-part manufacturers and loudspeaker manufacturers. The measurement methods provide parameters based on linear and nonlinear modelling of the suspension part and uses both static and dynamic techniques. It cancels and replaces IEC/PAS 62459 published in 2006. It constitutes a technical revision. The main changes are:
- descriptions of the methods of measurement are adjusted to the state of the technology;
- addition of Clauses 5 to 13;
- integration of Annex A in the main body of the standard;
- overall textual review.
The contents of the corrigendum of November 2015 have been included in this copy.

IEC 62458:2010 applies to transducers such as loudspeaker drive units, loudspeaker systems, headphones, micro-speakers, shakers and other actuators using either an electro-dynamical or electro-magnetic motor coupled with a mechanical suspension. The large signal behaviour of the transducer is modelled by a lumped parameter model considering dominant nonlinearities such as force factor, stiffness and inductance. It defines the basic terms and parameters of the model, the methods of measurements and the way the results should be reported. It cancels and replaces IEC/PAS 62458 published in 2006. It constitutes a technical revision. The main changes are:
- descriptions of the methods of measurement are adjusted to the state of the technology;
- addition of Clauses 4 to 15;
- integration of Annex A in the main body of the standard;
- overall textual review.

IEC 61606-1:2009 is applicable to the basic methods of measurement of the audio characteristics of the digital audio part of audio and audiovisual equipment for all of consumer use, professional use and personal computer. The common measuring conditions and methods, described in this standard, are used for the measurement of the performance characteristics of equipment having an audio bandwidth equal to approximately one-half of the sampling frequency of a system, where the audio information is processed in the form of digital data. CD players, DAT recorders, digital amplifiers, digital sound broadcast receivers and television broadcast receivers with digital sound are examples. It describes test methods for equipment which has digital input with analogue output and analogue input with digital output. Future revisions of this standard will cover digital-in/digital-out and analogue-in/analogue-out tests. It constitutes a technical revision. The significant technical changes with respect to the first edition are the following:
- changed the period of preconditioning;
- add A weighting filter in measuring instruments;
- correct the wrong reference number;
- some inappropriate descriptions have been improved.

IEC 61606-2:2009 is applicable to the basic measurement methods of the audio characteristics of the digital audio part of audio and audiovisual equipment for consumer use. It specify conditions and methods of measurement for consumer equipment.The common measuring conditions and methods are described in IEC 61606-1. It constitutes a technical revision. The significant technical changes with respect to the first edition are the following:
- changed the period of preconditioning;
- add A weighting filter in measuring instruments;
- correct the wrong reference number;
- some inappropriate descriptions have been improved.
This publication is to be read in conjunction with IEC 61606-1:2009.

IEC 61606-3:2008 is applicable to the basic measurement methods of audio equipment for professional use. The definitions, measuring conditions and methods common to both consumer and professional equipment are described in the IEC 61606-1. This standard contains details of definitions and measuring conditions and methods applicable to professional equipment which differ from those described in IEC 61606-1.
This publication is to be read in conjunction with IEC 61606-1:2009.

IEC 62503:2008 provides a subjective (or perceptible) and statistical method of assessment of overall, or end-to-end, difference of delays between real world and reproduced scenes in terms of video and accompanying audio recoded in a medium.

IEC/TS 62312-1-1 gives guidelines for methods of synchronization of audio and video and describes general measurement methods for the synchronization of audio and video equipment.

It gives guidelines for methods of synchronization of audio and video. It describes the system model and general methods for the synchronization of audio and video. The methods exclude the synchronization of the signal source and the spatial delay of audio reproduction.

IEC 61606-4:2005 specifies the basic measurement methods of a linear PCM signal for an audio part of personal computers (PCs) and applies to both desktop and portable computers. The common measuring conditions and methods are described in IEC 61606-1. Specific conditions and methods of measurement for PCs are given in this standard. This bilingual version (2012-05) corresponds to the monolingual English version, published in 2005-12.

Applies to loudspeakers conforming to IEC 61305-5 and intended for home use to establish standards for comparison of the sound characteristics of various loudspeakers with each other. Two test procedures are described: single stimulus ratings; paired comparisons.