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Authors
Abstract(s)
O objectivo principal deste estudo foi o de investigar como realizar a auralização interactiva de
excertos musicais executados por músicos através de um sistema electroacústico que respeite as
características de radiação tridimensionais dos instrumentos musicais. Este trabalho consistiu na
concepção teórica, implementação prática e validação experimental de um novo modelo para a
simulação de eventos acústicos com músicos em tempo real designado VW-system (Virtual Wall
System). O conceito de parede virtual baseado na síntese de apenas uma reflexão sonora através
de um binómio microfone/altifalante foi introduzido e o fenómeno da interacção
electroacústica foi discutido. O modelo foi avaliado objectiva e subjectivamente através de
várias metodologias, onde se incluem as medições electroacústicas e o trabalho experimental
com músicos.
O modelo proposto foi comparado com os métodos de auralização tradicionais de captação
monofónica e próxima do instrumento musical. Os resultados demonstraram uma maior
imunidade à realimentação electroacústica por parte do VW-system. Constatou-se que a utilização
de vários microfones afastados da fonte sonora não comprometem o ganho acústico potencial
do sistema, tornando possível a captação tridimensional do som do instrumento musical. Para
atingir esse objectivo, um novo método para a redução do eco provocado pela realimentação foi
proposto. Conseguiu-se uma atenuação de 32dB do eco que é independente do tempo e
intensidade da reflexão simulada. Estes resultados colocam o fenómeno da realimentação abaixo
do limiar da percepção humana definido na literatura.
O trabalho experimental realizado com instrumentistas a solo permitiu verificar que o VWsystem
pode ser implementado num espaço real para simular uma concha acústica virtual
aumentando desta forma a energia reflectida no palco. Verificou-se uma diferença mínima de
percepção média (JND) de 5dB para o parâmetro STearly da intensidade das primeiras reflexões
simuladas. Identificou-se que a condição acústica preferencial para uma situação de concerto
solo corresponde a um STearly compreendido entre -9 e -6dBA. Os resultados da comparação
subjectiva entre o modelo tradicional e o VW-system apontaram para uma sensação de maior
envolvência e naturalidade através do modelo proposto.
Durante a realização deste estudo foram desenvolvidas ferramentas informáticas na linguagem
de programação MAX/MSP para a operacionalização do sistema, estando disponíveis de forma
aberta à comunidade científica e profissional.
The main goal of this study was to understand how to create interactive auralization of musical segments played by musicians through an electroacoustic system that respects the three dimensional radiation characteristics of musical instruments. This work consisted in the theoretical development, practical implementation and experimental validation of a new model for the simulation of acoustic events with musicians in real time performance designated VWsystem (Virtual Wall System). The concept of a virtual wall based on the synthesis of one single sound reflection using a microphone/loudspeaker system was introduced and the phenomenon of the electroacoustic interaction was discussed. The model was evaluated both objectively and subjectively through several methodologies, including electroacoustic measurements as well as the experimental work with musicians. The proposed model was compared with the traditional auralization methods of a monophonic aquisition close to the musical instrument. The results showed a higher immunity to electroacoustic feedback from the VW-system. The use of several microphones placed far away from the sound source does not compromise the system potential acoustic gain, allowing the three-dimensional capture of the musical instrument’s sound. A new method for eco attenuation caused by feedback was proposed. An attenuation of 32dB of the echo was achieved which is independent from time and intensity of the simulated reflection. These results place the phenomenon of feedback below the threshold of human perception defined in the literature. The experimental work realized with solo instrumentalists confirmed that the VW-system can be implemented in a real space in order to simulate a virtual acoustic shell increasing in this way the energy reflected onto stage. An average Just Noticeable Difference (JND) of 5dB for the STearly parameter on the intensity of the early reflections simulated was obtained. The preferential acoustic condition for a solo concert situation corresponds to a STearly comprised between -9 and -6dBA was identified. The results of the subjective comparison between the traditional model and the VW-system pointed towards a feeling of greater envelopment and realistic behaviour through the proposed model. Along the realization of this work, several software tools were developed to operate the system using MAX/MSP programing language. These tools are available for use by the cientific and professional community.
The main goal of this study was to understand how to create interactive auralization of musical segments played by musicians through an electroacoustic system that respects the three dimensional radiation characteristics of musical instruments. This work consisted in the theoretical development, practical implementation and experimental validation of a new model for the simulation of acoustic events with musicians in real time performance designated VWsystem (Virtual Wall System). The concept of a virtual wall based on the synthesis of one single sound reflection using a microphone/loudspeaker system was introduced and the phenomenon of the electroacoustic interaction was discussed. The model was evaluated both objectively and subjectively through several methodologies, including electroacoustic measurements as well as the experimental work with musicians. The proposed model was compared with the traditional auralization methods of a monophonic aquisition close to the musical instrument. The results showed a higher immunity to electroacoustic feedback from the VW-system. The use of several microphones placed far away from the sound source does not compromise the system potential acoustic gain, allowing the three-dimensional capture of the musical instrument’s sound. A new method for eco attenuation caused by feedback was proposed. An attenuation of 32dB of the echo was achieved which is independent from time and intensity of the simulated reflection. These results place the phenomenon of feedback below the threshold of human perception defined in the literature. The experimental work realized with solo instrumentalists confirmed that the VW-system can be implemented in a real space in order to simulate a virtual acoustic shell increasing in this way the energy reflected onto stage. An average Just Noticeable Difference (JND) of 5dB for the STearly parameter on the intensity of the early reflections simulated was obtained. The preferential acoustic condition for a solo concert situation corresponds to a STearly comprised between -9 and -6dBA was identified. The results of the subjective comparison between the traditional model and the VW-system pointed towards a feeling of greater envelopment and realistic behaviour through the proposed model. Along the realization of this work, several software tools were developed to operate the system using MAX/MSP programing language. These tools are available for use by the cientific and professional community.