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v3.0, 20040325, ME

Session Z1 Saturday, May 8 09:30 h–11:00 h
Posters: Automotive Audio & Instrumentation and Measurement

Automotive Audio:
TANDEM Digital Audio AmplifierGiovanni Franceschini1, Alberto Bellini1, Antonio De Benedetti1, Michele Burlenghi1, Francisco Violi2
University of Parma, Parma, Italy
ASK Industries, Reggio Emilia, Italy
State-of-the art audio amplifiers can be classified into two major classes: linear amplifiers and switching amplifiers. The former class features low distortion but poor efficiency, while the latter features high efficiency coupled with high distortion and low bandwidth. In this paper a hybrid architecture is presented that combines linear and switching topology in order to obtain an audio amplifier featuring high efficiency, low distortion, and high bandwidth. The intrinsic structure of the switching stage allows an automatic spreading of the switching frequency, reducing EMI issues. A prototype amplifier was realized and tailored for automotive applications. The proposed architecture is patent pending.
Z1-2 Update to Automotive Doors as Loudspeaker EnclosuresRoger Shively, Josh King, Harman Becker Automotive Systems, Martinsville, IN, USA
This paper is an update to a previous study (Convention Paper 5752, presented at the AES 114th Convention), which used mechanical dynamic behavior data, impedance, and distortion measurements of several automotive doors to compare low-frequency performance and low-frequency sound quality. The updated information further investigates a methodology for quantifying door enclosures and refines the criteria for qualifying automotive doors as loudspeaker enclosures.
Z1-3 Evaluating Different Vehicle Audio Environments through a Novel Software-Based System—Stefano Squartini1, Francesco Piazza1, Romolo Toppi2, Massimo Navarri2, Walter Lori2, Ferruccio Bettarelli3, Emanuele Ciavattini3, Ariano Lattanzi3
Universitá Politecnica delle Marche, Ancona, Italy
Faital S.p.A, Milan, Italy
Leaff Engineering S.r.l., Jesi, Ancona, Italy
An original software-based system, featuring two different tools, is proposed for vehicle audio quality assessment. The first one performs the acquisition of relevant data for system modeling and canceling the undesired effects of the acquisition chain. The second offers a user-friendly interface for real-time simulation of different car audio systems and consequent subjective evaluation, where the listening procedure is directly experienced at a PC workstation. The validity of this approach has been examined through a subjective listening test set (more than 50 participants and 3 cars involved), developed by means of a dedicated software environment and based on appropriate ITU recommendations. Experimental results have shown that the quality rating delivered by conventional in-car procedure is confirmed when the software-based approach is used.

Instrumentation and Measurements:
Measurement of Active Speech Level Inside Cars Using a Throat-Activated MicrophoneFabio Bozzoli, Angelo Farina, University of Parma, Parma, Italy
One of the most used intelligibility parameters is the Speech Transmission Index (STI). The technique for determining it uses an artificial speaker and listener. When signal-to-noise ratio is particularly low, for example inside cars, the value of STI is mainly influenced by this ratio. Determining the sound power of actual speakers is the only way to correctly determine the artificial mouth. We have implemented a technique that is based on a throat-activated microphone, which is able to find the level of a real speaker’s voice inside the noisy spaces in effective conditions. We have particularly studied the speech inside cars and discovered how the value defined by norms may be extremely different from the real one. In this way, we have been able to produce more reliable excitation signals.
Z1-5 The Use of Continuous Phase for Interpolation, Smoothing, and Forming Mean Values of Complex Frequency Response CurvesJoerg Panzer1, Lampos Ferekidis2
Consultant, Salgen, Germany
Consultant, Barsinghhausen, Germany
The direct application of interpolation, smoothing or mean-value algorithms to complex-valued frequency response data may cause interference patterns and, because to this, does not yield the expected result. This paper demonstrates the effect of the use of continuous phase in a variety of applications such as interpolation between two frequency response curves, complex smoothing with down-sampling using a logarithmic grid, and forming mean values of a set of complex frequency response curves. The continuous phase-approach takes into account the multivalued property of the exponential function of the phase term.
Z1-6 Web-Based Acoustic Noise Measurement SystemAndrzej Czyzewski, Jozef Kotus, Gdansk University of Technology, Gdansk, Poland
The concept and implementation of a multimedia computer system for the monitoring of environmental noise threats is presented. The principal aim of the project is to improve the effectiveness of prophylaxis of hearing diseases. This system makes it possible to receive, store, analyze, and visualize noise data coming from noise measurement equipment and from electronic questionnaires accessible through the Internet. A new concept of the USB noise meter with GPS is also presented.
Z1-7 Software Application for Electroacoustic Measurements Using the Time-Delay Spectrometry (TDS) Method—Evaggelos Parlantzas, Charalampos Dimoulas, George Kalliris, George Papanikolaou, Christos Sevastiadis, Aristotle University of Thessaloniki, Thessaloniki, Greece
This paper presents a software application that conducts electroacoustic measurements using a digital approach to time-delay spectrometry. Development is focused on simplified hardware requirements such as a personal desktop or laptop computer. A friendly and flexible user interface has been designed. Linear and logarithmic sweep test signals are generated and reproduced. System under test (e.g., room) response is recorded and stored in the hard disk. Energy time curve (ETC) and frequency domain analysis procedures are guided efficiently. Reverberation time in the case of a room is estimated very quickly. All task data may be restored later for further analysis. Finally, the results of comparison measurements using our application to measurements with a widely accepted TDS analyzer are presented.
Z1-8 Triode SimulatorDimitri Danyuk, Digital Research Labs, haverhill, MA, USA
The design for a low-noise amplifier is presented. The amplifier has a tube-like transfer characteristic and produces harmonic distortion components that are similar to triode preamplifiers.

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