AES New York 2013
Engineering Brief EB5
EB5 - E-Brief Posters—Part 2
Saturday, October 19, 5:00 pm — 6:30 pm (1EFoyer)
EB5-1 Digital Model of the Passive James/Baxandall Tonestack—Christopher Bennett, University of Miami - Coral Gables, FL, USA; Oygo Sound LLC - Miami, FL, USA; Jonathon Toft-Nielsen, Intelligent Hearing Systems - Miami, FL, USA; Connor McCullough, University of Miami - Coral Gables, FL, USA
E. J. James described a two-knob tone control in 1949 with easily selectable boost/cut depths as well as cutoff frequencies. This design was later popularized by P. J. Baxandall to provide negative feedback in active circuits, and was subsequently popular in many high-end amplifiers. Here, the authors analyzed the circuit in the s-domain, preserving parametric control of bass and treble potentiometer values. Poles and zeros were found using Ferrari’s solution to a quartic equation, followed by bilinear transformation to the z-domain, and finally lumping into second-order sections to produce a computationally efficient and faithful emulation of this classic tonestack.
Engineering Brief 124 (Download now)
EB5-2 Automatic Analog Preamp Gain Control Using Digital Command—Nicolas Sturmel, Digigram S.A. - Montbonnot Saint Martin, France; Fusheng Yu, ENSEEIHT–INP - Toulouse, France
Automatic Gain Control (AGC) is a common tool for field recording, but it usually requires specific hardware such as voltage controlled amplifiers. In this paper, we address the problem of designing an AGC when none of this hardware is present, using an ubiquitous digitally controlled high end analog preamp. To do this, we have to overcome two problems: fixed gain steps and variable delay of the gain command. In order to propose an efficient solution, we will first study the effects of each of those two problems. Finally, a very simple digitally controlled automatic gain, but of high quality will be proposed, using only 10MIPS of processing power from our high end USB sound card.
Engineering Brief 125 (Download now)
EB5-3 Testing Watermark Robustness against Application of Audio Restoration Algorithms—Bozena Kostek, Gdansk University of Technology - Gdansk, Poland; Audio Acoustics Lab.; Janusz Cichowski, Gdansk University - Gdansk, Poland; Andrzej Czyzewski, Gdansk University of Technology - Gdansk, Poland
The purpose of this study was to test to what extent watermarks embedded in distorted audio signals are immune to audio restoration algorithm performing. Several restoration routines such as noise reduction, spectrum expansion, clipping or clicks reduction were applied in the online website system. The online service was extended with some copyright protection mechanisms proposed by the authors. They contain low-level music features embedded as watermarks using the non-blind approach. After applying restoration algorithms, the watermark is extracted from the audio track. It was shown in experiments, that a watermark “attacked” by the restoration procedures may still be detected. However in some cases it is possible to retrieve only a binary information about the watermark presence in the audio carrier.
Engineering Brief 126 (Download now)
EB5-4 PsychoMasker: An iOS Application for the Visualization of PsychoAcoustic Principles—Andrew Ayers, University of Miami - Coral Gables, FL, USA; Robert Rehrig, University of Miami - Coral Gables, FL, USA; Christopher Bennett, University of Miami - Coral Gables, FL, USA; Oygo Sound LLC - Miami, FL, USA; Colby N. Leider, University of Miami - Coral Gables, FL, USA
The concept of masking in psychoacoustics has invaded the daily lives of almost every audio listener since the initial release of the MPEG-1 standard. With the ubiquity of the MP3, the consumption of
perceptually coded audio is impossible to avoid. While many people understand the concept of perceptual coding, it can be difficult to visualize what is actually happening to the information in the audio files. PsychoMasker is an App that provides real-time visualization of the psychoacoustic principles used in MPEG encoding to anyone with an iPad. The PsychoMasker App shows the user how the encoding process
aff ects any song in the user's iTunes library step-by-step.
Engineering Brief 127 (Download now)
EB5-5 Using MIDI Control Surfaces with MATLAB Programs and Simulink—Charlie DeVane, MathWorks - Natick, MA, USA
MATLAB and Simulink are widely used in the design of software and hardware for audio products. MATLAB programs and Simulink models can simulate signal processing algorithms, control logic, and other aspects of the system design in real time, yielding substantial improvements in designer productivity and product quality. When exploring a new algorithm or product concept, designers often need to simultaneously tune multiple system parameters while simulating. This can become cumbersome using GUIs, but MIDI control surfaces provide a natural, intuitive interface, further enhancing the designer's work flow. In some work flows, such as rapid prototyping, MIDI control surfaces can eliminate the need to create a GUI. Using numerous examples, including a simple reverberator, this brief shows how to use MIDI control surfaces to interactively control running MATLAB programs and Simulink models.
Engineering Brief 128 (Download now)
EB5-6 MIDI to CV Conversion Using a Livid BrainV2 and I2C Protocol—Mark Gill, University of Miami - Coral Gables, FL, USA
Bob Moog developed Control voltage (CV) in the 1960s. His introduction of CV called for an oscillator’s pitch to vary at the rate of 1 volt per octave. This scheme is widely used today in analog circuits, and can be mimicked digitally. The CV output is determined by converting various MIDI messages including USB MIDI, and physical controls including analog potentiometer inputs and momentary on, momentary off buttons. The Livid BrainV2 handles all the MIDI inputs and directs them to a digital to analog converter to create the CV signal controlled by I2C communication. This paper documents the hardware used to create the converter, the mathematical onsiderations for conversion, and techniques used to overcome the limited ability of 8-bit MIDI messages to be portrayed as an analog signal. Sound clips are available at my website markolgill.com
Engineering Brief 129 (Download now)
