Memorial Lecture at 147th: Louis Fielder / Psychoacoustics Applied to Dynamic-Range and Nonlinear-Distortion Assessment

AES 147th Convention
Javits Center, New York, NY, USA.
October 16–19, 2019

Thursday, October 17th 2019 at 6.30 pm

Louis D. Fielder, AES Silver Medal holder, will present the 41st Richard C. Heyser Memorial Lecture during the 147th Convention

Psychoacoustics Applied to Dynamic-Range and Nonlinear-Distortion Assessment

The psychoacoustics of noise detection, measurements of noise in the digital-audio recording‑storage‑reproduction chain, and measurements of peak-acoustic pressures in music performances are combined to determine the requirements for noise-free reproduction of music. It is found that the required ratio between the maximum reproduction levels and the perceived audibility of noise can be as much as 124 decibels. When more practical circumstances are considered, this requirement is shown to drop to more feasible values. Next, the concept of auditory masking is introduced to allow for the assessment of nonlinear distortions in digital-audio conversion systems operating at low‑signal levels and then several examples of digital-audio conversion systems are examined. Finally, an expanded use of masking and a model to calculate a total nonlinear-distortion audibility number are used to determine the audibility of nonlinear distortions in headphones when driven by sine-wave signals at or below 500 Hz. Examples of headphone distortion assessment are examined and extension of this measurement technique to low-frequency loudspeaker evaluation is also discussed.


Louis Fielder received a BS. degree in electrical engineering from the California Institute of Technology in 1974 and an MS. degree in acoustics from the University of California in Los Angeles in 1976.

During the period between 1976– 1978 he worked on electronic component design for custom sound‑reinforcement systems at Paul Veneklasen and Associates. From 1978 – 1984 he was involved in digital-audio and magnetic recording research at the Ampex Corporation. At that time he became interested in applying psychoacoustics to the design and analysis of digital-audio conversion systems. From 1984–2018 he has worked at Dolby Laboratories on the application of psychoacoustics to the development of audio systems and on the development of a number of bit-rate reduction audio coders for music distribution, transmission, and storage applications, i.e. AC-1, AC-2, AC-3, Enhanced AC-3, AAC, and Dolby E. Additionally, he has investigated perceptually derived limits for the performance for digital‑audio conversion, low-frequency loudspeaker systems, distortion limits for loudspeakers/headphones, loudspeaker-room equalization, and headphone virtualization. He managed the Sound Technology Research Department at Dolby Laboratories in San Francisco from 2005 – 2009.

Louis Fielder is a life fellow of the AES, a recipient of the AES Silver Medal, a senior life member of the IEEE, a life member of the SMPTE, and an emeritus member of the Acoustical Society of America. He was on the AES Board of Governors during 1990–1992, President during 1994 – 1995, and Treasurer 2005 – 2009.

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