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AES Amsterdam 2008
Paper Session P19

P19 - Software, Instrumentation, and Measurement

Monday, May 19, 12:30 — 15:30
Chair: John Vanderkooy, University of Waterloo - Waterloo, Ontario, Canada

P19-1 Graphical Control of a Parametric EqualizerJörn Loviscach, Hochschule Bremen (University of Applied Sciences) - Bremen, Germany
Graphic equalizers allow the user to define a filter’s magnitude response virtually free of restrictions. Parametric equalizers are much more limited. However, they offer some vital advantages over graphic equalizers, such as consuming less computational power and operating minimally invasively with naturally soft magnitude and phase responses. This paper aims at combining the best of both worlds. It presents a range of methods to control a digital parametric equalizer graphically through a curve or a collection of anchor points. While the user is editing the graphical input, an optimization process runs in the background and adjusts the equalizer’s parameters to reflect the input. In addition, the number of bands and their type (shelving/peak) can be adjusted automatically to produce a simple solution.
Convention Paper 7437 (Purchase now)

P19-2 Audio Software Development—An Audio Quality PerspectiveJonas Ekeroot, Jan Berg, Luleå University of Technology - Piteå, Sweden
When developing audio applications, different choices on software implementation aspects influence the total audio software signal path and can be of importance from an audio quality perspective. The field is not well documented in the literature. A study was carried out aiming at identifying relevant questions that must be considered. The general development perspective was on audio software written in C++ to be run on general purpose CPUs. A research review, comprising literature from different fields such as audio engineering, computer science, and software engineering was conducted to summarize and integrate an overview of the field. The result can be viewed as a map of questions for future research activities, consisting of further literature studies and experiments with software prototypes.
Convention Paper 7438 (Purchase now)

P19-3 Multi Carrier Modulator for Switch-Mode Audio Power AmplifiersArnold Knott, Harman/Becker Automotive Systems GmbH - Straubing, Germany, and Technical University of Denmark, Lyngby, Denmark; Gerhard Pfaffinger, Harman/Becker Automotive Systems GmbH - Straubing, Germany; Michael A. E. Andersen, Technical University of Denmark - Lyngby, Denmark
While switch-mode audio power amplifiers allow small implementations and high output power levels due to their high power efficiency, they are very well known for creating electromagnetic interference (EMI) with other electronic equipment, in particular radio receivers. Lowering the EMI of switch-mode audio power amplifiers while keeping the performance measures to excellent levels is, therefore, of high general interest. A modulator utilizing multiple carrier signals to generate a two level pulse train will be shown in this paper. The performance of the modulator will be compared in simulation to existing modulation topologies. The lower EMI as well as the preserved audio performance will be shown in simulation as well as measurement results of a prototype.
Convention Paper 7439 (Purchase now)

P19-4 A Comparison of Theoretical, Simulated, and Experimental Results Concerning the Stability of Sigma Delta ModulatorsGeorgi Tsenov, Valeri Mladenov, Technical University of Sofia - Sofia, Bulgaria; Joshua D. Reiss, Queen Mary, University of London - London, UK
Sigma delta modulation is a popular form of audio analog-to-digital and digital-to-analog conversion, but suffers from stability problems for many designs and many input signals. A general theory of stability in sigma delta modulators has been developed that predicts the stability of a high order one-bit sigma-delta modulator (SDM) under a variety of designs. In this paper the theoretical approach to stability as it applies to boundedness of states is explained. Several low pass SDM designs are developed that are intended for audio analog to digital conversion, and predicted results for stability of these designs are given. Stability is examined both in terms of the maximum allowable DC input amplitude and the theoretical sufficient conditions for stable behavior. Theoretical results are compared with simulated results, and where possible, with experimental results from a realization of a third order SDM with adjustable parameters. Practical observations are then made concerning the effect of noiseshaping, pole/zero placement, and cut-off frequency on the stability.
Convention Paper 7440 (Purchase now)

P19-5 A New Method for Identification of Nonlinear Systems Using MISO Model with Swept-Sine Technique: Application to Loudspeaker AnalysisAntonín Novák, Czech Technical University in Prague - Prague, Czech Republic, and Université du Main, Le Mans, France; Laurent Simon, Pierrick Lotton, Université du Main - Le Mans, France; Frantisek Kadlec, Czech Technical University in Prague - Prague, Czech Republic
This paper presents a Multiple Input Single Output (MISO) nonlinear model in combination with sine-sweep signals as a method for nonlinear system identification. The method is used for identification of loudspeaker nonlinearities and can be applied to nonlinearities of any audio components. It extends the method based on nonlinear convolution presented by Farina, providing a nonlinear model that allows simulation of the identified nonlinear system. The MISO model consists of a parallel combination of nonlinear branches containing linear filters and memory-less power-law distortion functions. Once the harmonic distortion components are identified by the method of Farina, the linear filters of the MISO model can be derived. The practical application of the method is demonstrated on a loudspeaker.
Convention Paper 7441 (Purchase now)

P19-6 Junction Identification Using Acoustic ReflectometryAdam Kestian, Agnieszka Roginska, New York University - New York, NY, USA
Acoustic reflectometry is a non-invasive, time-domain method of identifying the geometry of an acoustical space. A sound pulse is injected into a space and the resulting impulse response details particular changes of impedance. In the present paper acoustic reflectometry is utilized to identify scattering junctions of geometric spaces. Most notably, the four most common types of scattering junctions are identified: a cross-sectional increase, cross-sectional decrease, L-intersection, and T-intersection.
Convention Paper 7442 (Purchase now)

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