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AES Section Meeting Reports

Argentina - November 3, 2011

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Summary

On September 29th 2011, the auditorium at Estudio Urbano, in Buenos Aires, was chosen for the start of the "Second Series of Open Conferences in Estudio Urbano; Audio & Acoustics", organized once again by AES Argentina.
This Series consist of a total of ten Seminars from different keynote speakers, each specialized in diverse areas of audio and acoustics, and taking place every Thursday from September 29th until December 1st.

On november 3th, three young engineers from the Acoustic and Electro-acoustic Laboratory of the University of Buenos Aires presented their work in the field of new audio technology. Here´s each of their paper presentations abstracts:

Pablo Gomez - Ionic Transduction System
The challenge of every sound transducer is to as closely as possible achieve the convertion of an acoustic signal into an electrical signal or vice versa.
Transducer-associated moving parts introduce distortions inherent to the mechanical system, including spurious modes of vibration of the diaphragm and Doppler distortion. To eliminate such distortions, mechanical moving parts must be avoided. For this reason, we intend to use a system based on the generation of plasma in the air. Transduction systems for air ionization have an associated number of problems (ozone generation, high-energy, background noise, etc.), making them commercially unviable. The aim of this paper is to study and improve the state of the art in transduction systems by ionizing air. The first stage will meet the necessary measuring instruments. Then numerical simulation tools used to study the system and define the design of the transducer to be tested will be implimented. From the experimental results are obtained, solutions will be formulated to effectively alleviate the problems associated with such systems.

Martin Harris - Alternative Geometries For Electrostatic Loudspeakers
Loudspeakers are electrodynamic electroacoustic devices that can not provide a reasonably flat response in the range of work without a comprehensive design or introducing colour to reproduced signals. Investigation on the electrostatic loudspeaker technology (ELS) is proposed, due to it's design being expected to exceed the electrodynamic characteristics in their inherent qualities. The advantages of electrostatic loudspeakers lie in the extremely small mass per unit area of the diaphragm and the force acting upon it being evenly distributed, as generated by the fluctuating electric field. Under efficiently controlled parasitic resonances, excellents speakers with great frequency response and phase coherence can be achieved. Beyond operational concepts, the investigation is aimed at searching alternatives to the different geometries commonly applied, in order to further minimize the impacts of the diaphragm, therefore creating an effect that really qualifies as "high end".

Lucas Rubinstein - Amplifier For Pulse Width Modulation (PWM) Control In One Cycle And Non-resettable Integrator
One of the topologies currently used in amplifiers by PWM is the "control cycle" or OCC (One Cycle Control).
In these amplifiers, the reference signal for the modulation signal is obtained by integrating the pulse until it equals the value of the input signal or any related error signal input. This significantly reduces harmonic distortion in the device, as variations in supply voltage and other changes in the output pulses are integrated together with the pulse signal to reach the desired value. This occurs for each cycle of the reference signal, hence the name of control in a cycle. The main problem with this topology lies in the integrator, as the initial value after reset it is influenced by its past history. The design of an OOC amplifier holding an integrator that does not need to be reset (and so eliminate these problems) is proposed.

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