S20  Vibroacústica    Titulo: CARACTERIZAÇÃO DE MATERIAIS PARA MODELAGEM NUMÉRICA DE DIAFRAGMAS DE ALTO-FALANTES   Resumo : MATERIAL CHARACTERIZATION FOR THE NUMERICAL MODELING OF LOUDSPEAKER DIAPHRAGMS ABSTRACT. ONE OF THE MAIN DIFFICULTIES IN THE DESIGN STAGE OF LOUDSPEAKERS IS THE PREDICTION OF ITS DYNAMIC ACOUSTICAL RESPONSE AT MEDIUM AND HIGH FREQUENCIES. A LOUDSPEAKER DIAPHRAGM WORKS AS A RIGID PISTON UP TO A CERTAIN FREQUENCY. ABOVE THIS FREQUENCY, PEAKS AND DIPS SHOW UP IN THE RESPONSE SPECTRUM, WHICH CHARACTERIZE THE LOUDSPEAKER TIMBRE. THE NUMERICAL MODELING OF LOUDSPEAKER DIAPHRAGMS HAS BECOME, IN RECENT YEARS, A VALUABLE TOOL IN QUALITY LOUDSPEAKER DESIGN. THE NUMERICAL MODELING MAY BE PERFORMED USING METHODS SUCH AS THE FINITE ELEMENT AND BOUNDARY ELEMENT METHODS. IN ORDER TO MODEL THE DIAPHRAGM NUMERICALLY USING ONE OF THESE METHODS IT IS NECESSARY TO CHARACTERIZE THE BEHAVIOR OF THE MATERIALS INVOLVED. THE MATERIALS OF WHICH LOUDSPEAKERS ARE MADE OF ARE NON CONVENTIONAL AND, THEREFORE, THEIR MATERIAL PROPERTIES HAVE TO BE DETERMINED EXPERIMENTALLY. THE MAIN OBJECTIVE OF THIS PAPER IS TO SHOW RESULTS OF MATERIAL PROPERTY DETERMINATION USING DIFFERENT EXPERIMENTAL METHODS. THE RESULTS ARE USED WITH A COMMERCIAL FINITE ELEMENT CODE TO MODEL A LOUDSPEAKER DIAPHRAGM. DIAPHRAGM MODES PREDICTED WITH THE FINITE ELEMENT ANALYSIS ARE COMPARED WITH EXPERIMENTAL MODAL ANALYSIS RESULTS. THE VELOCITIES OVER THE DIAPHRAGM SURFACE WERE MEASURED USING A LASER DOPPLER VIBROMETER. KEYWORDS: LOUDSPEAKER, ACOUSTICS, MODAL ANALYSIS, DIAPHRAGM, MATERIAL PROPERTIES     Autores : Arruda, José Roberto de França Ferreira, Rodrigo José Hernandes, Cristiane Silveira Hernandes, Cristiane Silveira     Trabalho Completo :   COBEM99 | Comissão  Organizadora | Palestras | Sessões Técnicas | Autor | Simpósios e Sessões Especiais | Revisores |  Título  dos  Trabalhos | Local