Digital Audio Papers
The contents of some of these papers are available electronically
in Adobe PDF format by following the links. The others are available through
the Audio Engineering Society.
If you have problems getting these papers then please contact firstname.lastname@example.org.
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96 kHz Digital Audio
Abstract: Reports that 96 kHz sampled digital audio systems have greater
transparency than those sampling at 44.1 kHz apparently conflict with knowledge
of the capability of human hearing. The band-limiting filters required are examined
for a role in producing these differences. Possible mechanisms are presented for
these filters to produce audible artefacts and filter designs avoiding these artefacts
Julian Dunn - `The benefits of 96 kHz sampling rate formats
for those who cannot hear above 20 kHz' Preprint 4734, presented at the
104th AES Convention, Amsterdam, May 1998.
Interfacing and Jitter
Interfacing Digital Audio Equipment to the Standards AES3, AES5, AES11
Abstract: The implications of various parts of the digital audio
interface are critically examined. Some specific design approaches are
recommended for implementing the interface and some additional specifications
are suggested for the system designer to consider.
Julian Dunn - `Considerations for Interfacing Digital Audio
Equipment to the Standards AES3, AES5, AES11' Published in `Images of Audio',
the Proceedings of the 10th International AES Conference, London, September
1991. pp 115-126.
Abstract: Timing jitter in digital audio equipment can subtley degrade
the audio quality or even cause data transmission failure. This paper examines
the jitter performance requirements for digital audio equipment in the
context of the audibility of sampling jitter modulation effects and the
digital audio interface specification. It concludes by presenting techniques
for the measurement of jitter performance.
Julian Dunn - `Jitter: Specification and Assessment in Digital
Audio Equipment'. Preprint 3361, presented at the 93rd AES Convention,
San Francisco, October 1992.
Abstract: An ad-hoc Task Group within the SC-2-2 (Digital Input/Output
Interfacing) Working Group is developing a more detailed specification
for jitter in the embedded clock of the digital audio interface signal.
The discussion and the intermediate conclusions of this work are presented
in this paper as an invitation for informal comment and debate about the
Julian Dunn, Barry McKibben, Roger Taylor and Chris Travis
- `Towards Common Specifications for Digital Audio Interface Jitter' Preprint
3705, presented at the 95th AES Convention, New York, October 1993.
Abstract: Timing jitter can cause the failure of a digital audio
interface, or subtle degradation in the quality of an A-D or D-A conversion.
This paper presents measurement techniques which can be used in the diagnosis
and analysis of jitter-related problems, and gives examples of their application.
Julian Dunn and Ian Dennis - `The Diagnosis and Solution
of Jitter-Related Problems in Digital Audio' Preprint 3868, presented at
the 96th AES Convention, Amsterdam, February 1994.
Jitter and Digital Audio
Abstract:It is well known that timing jitter in digital audio converters
can subtly degrade performance. Unfortunately standard audio measurements
are not very useful for assessing sensitivity to jitter. Mathematical formulae
are derived to relate the modulation artifacts produced by sampling jitter
with the jitter amplitude and frequency. The audibility of these modulation
artifacts is considered in relation to the jitter spectral content. After
examining the main sources of jitter in digital audio systems, measurement
techniques appropriate to assessing the sensitivity to each source are
described. Results of these measurements are shown for some digital audio
Julian Dunn - 'Jitter and Digital Audio Performance Measurements',
Published in `Managing the Bit Budget', the Proceedings of the AES UK Conference,
London, 16-17 May 1994.
Abstract: The asynchronous clocks within the IEEE1394 high performance
serial bus present challenges for sample timing recovery in conjunction
with the transmission of digital audio. Moreover the systematic nature
of the jitter produced means that prototype systems are unlikely to produce
worst-case performance. This is analysed and, with jitter audibility models
developed elsewhere, a sampling jitter attenuation requirement is estimated.
Julian Dunn – ‘Sample clock jitter and real-time audio over
the IEEE1394 high performance serial bus.’ Preprint 4920, presented at
the 106th AES Convention, Munich, May 1999
IEEE1394 and Sampling Jitter
Abstract: Timing fluctuations, or jitter, in clocks can degrade
audio quality when the clocks are used in analogue to digital or digital
to analogue conversion. The asynchronous clocks within the IEEE1394 high
performance serial bus produce jitter. This may present challenges for
low jitter sample clock recovery in conjunction with the transmission of
digital audio using that bus and so the nature of this jitter requires
investigation. Measurements of recovered clock jitter in a simple system
are presented which confirm the results of a previous simulation of jitter
generation mechanisms. Possible engineering solutions are discussed.
Julian Dunn - 'IEEE1394 and sampling jitter' Published in
`Moving Audio', the Proceedings of the AES UK Conference, London, 8-9 May
2000. pp 47-62.
High Dynamic Range Digital Audio
Abstract: Application of digital signal processing to audio is often
limited by available converter technology and recorder datawidth to processes
controlled dynamic range. In digital mixing consoles some analogue gain
control is normally required to achieve adequate performance for the input
channel ADCs and digital multi-track recorders.
Julian Dunn - 'High Dynamic Range Audio Applications for
Digital Signal Processing '. Preprint 3434, presented at the 93rd AES Convention,
San Francisco, October 1992.
Of The Sonic Differences Between Numerically Identical Compact Discs
Abstract: It has been observed that CD media apparently containing
identical data can have varying subjective sound qualities on replay. It
is difficult to suggest a theoretical basis for this. This paper describes
an analytical study of a variety of CD media and players in an attempt
to identify the differences and to isolate their causes. The research is
still in progress.
Ian Dennis, Julian Dunn and Doug Carson'An Investigation
Of The Sonic Differences Between Numerically Identical Compact Discs Preprint
4399, presented at the 101st AES Convention, Los Angeles, November 1996.
In 2001 Audio
Precision, a US audio test & measurement manufacturer, asked Julian
to write a book on digital audio measurement. This book quickly became a definitive
resource for design engineers working in the field of digital audio the world
over. In his classic tradition, the book covered the subject material in sufficient
depth to be valuable to advanced readers while presenting the information in
a way that a novice could grasp the concepts. The book is in its second printing
in English; a Japanese translation was published in February 2004.
Techniques for Digital Audio
focuses on the measurement of digital audio signals, and examines in great detail
both techniques used to evaluate the performance of the converters and the digital
interface signal that carries the audio.
- Chapter One,
Jitter Theory, studies the causes and effects of the interface
timing variations called jitter with a number of tests designed to
characterize this problem.
- Chapter Two,
Analog-to-Digital Converter Measurements, looks at key ADC parameters
and behavior and includes 15 AP Basic macros to run the necessary tests.
- Chapter Three,
Digital-to-Analog Converter Measurements, does the same for DACs.
A sidebar looks at dither. Twenty-five macros are included.
- Chapter Four,
The Digital Interface, discusses the AES3/IEC60958 digital interface,
examining the basic format and the means of characterizing the signal. Sidebars
focus on the international standards and on synchronization considerations.