Beam-steerng digital num array paramétrico

Mestrado em Engenharia Electrónica e TelecomunicaçõesActualmente existem diversos m etodos que permitem a realiza c~ao de beamsteering num altifalante param etrico. No entanto, a maioria dos m etodos e incapaz de proporcionar uma elevada resolu c~ao angular usando um projecto de hardware e ciente. Mais ainda, poucos s~ao os sistemas que proporcionam um controlo do beam de pot^encia em tempo real. Neste documento, e proposta uma nova abordagem para colmatar estes problemas tirando partido da alta frequ^encia inerente a modula c~ao sigmadelta. Esta implementa c~ao leva a um projecto compacto que proporciona uma elevada resolu cao angular associada a uma solu c~ao de baixo custo e com baixo consumo de pot^encia devido ao uso de apenas uma DAC sigmadelta. O sistema implementado sobre FPGA alia a natural alta frequ^encia dum modulador sigma-delta ao uso dum unico shift-register para introduzir os atrasos necess arios a realiza c~ao de beam-steering. A escolha do atraso adequado e feita com o uso de multiplexers que encaminham os diversos sinais sigma-delta para as sa das do sistema desejadas.Several methods enable a steerable beam using an parametric loudspeaker. However, many of them are not able to use a high angular resolution with an e cient design. More, even the ability to change the beam steering in real time is neglected by several methods. In this document, we propose a new approach to the beam-steering problem using the intrinsic high frequency of a sigma-delta digital to analog converter conjugated with online con gurable digital delays obtained only through a programmable wide shift-register. This implementation leads to a real time beam-steering with a simple digital processing block that enables a high resolution angle. Additionally the use of a sigma-delta DAC provides a low-cost, highly integrated and energy e cient system using only a DAC. The implemented system takes advantage of the high frequency of the digital signal from the sigma-delta modulator allied with the use of a shiftregister to obtain the ne time delays necessary to do the beam-steering. The several outputs delays are chosen between the sigma-delta signals in the shift-register using a group of multiplexers

Beam-steering digital num array paramétrico

Engenharia Electrónica e TelecomunicaçõesActualmente existem diversos m etodos que permitem a realiza c~ao de beamsteering num altifalante param etrico. No entanto, a maioria dos m etodos e incapaz de proporcionar uma elevada resolu c~ao angular usando um projecto de hardware e ciente. Mais ainda, poucos s~ao os sistemas que proporcionam um controlo do beam de pot^encia em tempo real. Neste documento, e proposta uma nova abordagem para colmatar estes problemas tirando partido da alta frequ^encia inerente a modula c~ao sigmadelta. Esta implementa c~ao leva a um projecto compacto que proporciona uma elevada resolu cao angular associada a uma solu c~ao de baixo custo e com baixo consumo de pot^encia devido ao uso de apenas uma DAC sigmadelta. O sistema implementado sobre FPGA alia a natural alta frequ^encia dum modulador sigma-delta ao uso dum unico shift-register para introduzir os atrasos necess arios a realiza c~ao de beam-steering. A escolha do atraso adequado e feita com o uso de multiplexers que encaminham os diversos sinais sigma-delta para as sa das do sistema desejadas.Several methods enable a steerable beam using an parametric loudspeaker. However, many of them are not able to use a high angular resolution with an e cient design. More, even the ability to change the beam steering in real time is neglected by several methods. In this document, we propose a new approach to the beam-steering problem using the intrinsic high frequency of a sigma-delta digital to analog converter conjugated with online con gurable digital delays obtained only through a programmable wide shift-register. This implementation leads to a real time beam-steering with a simple digital processing block that enables a high resolution angle. Additionally the use of a sigma-delta DAC provides a low-cost, highly integrated and energy e cient system using only a DAC. The implemented system takes advantage of the high frequency of the digital signal from the sigma-delta modulator allied with the use of a shiftregister to obtain the ne time delays necessary to do the beam-steering. The several outputs delays are chosen between the sigma-delta signals in the shift-register using a group of multiplexers

Advances in Architectural Acoustics

Satisfactory acoustics is crucial for the ability of spaces such as auditoriums and lecture rooms to perform their primary function. The acoustics of dwellings and offices greatly affects the quality of our life, since we are all consciously or subconsciously aware of the sounds to which we are daily subjected. Architectural acoustics, which encompasses room and building acoustics, is the scientific field that deals with these topics and can be defined as the study of generation, propagation, and effects of sound in enclosures. Modeling techniques, as well as related acoustic theories for accurately calculating the sound field, have been the center of many major new developments. In addition, the image conveyed by a purely physical description of sound would be incomplete without regarding human perception; hence, the interrelation between objective stimuli and subjective sensations is a field of important investigations. A holistic approach in terms of research and practice is the optimum way for solving the perplexing problems which arise in the design or refurbishment of spaces, since current trends in contemporary architecture, such as transparency, openness, and preference for bare sound-reflecting surfaces are continuing pushing the very limits of functional acoustics. All the advances in architectural acoustics gathered in this Special Issue, we hope that inspire researchers and acousticians to explore new directions in this age of scientific convergence

Effects of errorless learning on the acquisition of velopharyngeal movement control

Session 1pSC - Speech Communication: Cross-Linguistic Studies of Speech Sound Learning of the Languages of Hong Kong (Poster Session)The implicit motor learning literature suggests a benefit for learning if errors are minimized during practice. This study investigated whether the same principle holds for learning velopharyngeal movement control. Normal speaking participants learned to produce hypernasal speech in either an errorless learning condition (in which the possibility for errors was limited) or an errorful learning condition (in which the possibility for errors was not limited). Nasality level of the participants’ speech was measured by nasometer and reflected by nasalance scores (in %). Errorless learners practiced producing hypernasal speech with a threshold nasalance score of 10% at the beginning, which gradually increased to a threshold of 50% at the end. The same set of threshold targets were presented to errorful learners but in a reversed order. Errors were defined by the proportion of speech with a nasalance score below the threshold. The results showed that, relative to errorful learners, errorless learners displayed fewer errors (50.7% vs. 17.7%) and a higher mean nasalance score (31.3% vs. 46.7%) during the acquisition phase. Furthermore, errorless learners outperformed errorful learners in both retention and novel transfer tests. Acknowledgment: Supported by The University of Hong Kong Strategic Research Theme for Sciences of Learning © 2012 Acoustical Society of Americapublished_or_final_versio