Search results for "acústica"
showing 10 items of 28 documents
Acoustic properties and perception of minimal contrasts in Valencian Catalan sibilants
2017
El valencià estàndard presenta tres consonants fricatives sibilants: /s/, /z/ i /S/.Mentre que el contrast entre /z/ i /s/ sembla indiscutible, l’existència d’unaoposició real entre /S/ i /s/ és més dubtosa. El primer objectiu d’aquest treball éscomprovar si, en un estil de parla hiperarticulat (Fonet, Gonzàlvez et al., 2007), laconsonant /s/ és diferent de /z/ i de /S/ tenint en compte set paràmetres acústics:durada, harmonicitat, pic espectral i quatre moments espectrals: centre de gravetat,desviació estàndard, asimetria i curtosi. Les dades revelen que /z/ i /s/ contrastenclarament en durada, harmonicitat i asimetria; /S/ i /s/ contrasten en harmonicitat,desviació estàndard, curtosi i, e…
Polarized recombination of acoustically transported carriers in GaAs nanowires
2012
: The oscillating piezoelectric field of a surface acoustic wave (SAW) is employed to transport photoexcited electrons and holes in GaAs nanowires deposited on a SAW delay line on a LiNbO3 crystal. The carriers generated in the nanowire by a focused light spot are acoustically transferred to a second location where they recombine. We show that the recombination of the transported carriers occurs in a zinc blende section on top of the predominant wurtzite nanowire. This allows contactless control of the linear polarized emission by SAWs which is governed by the crystal structure. Additional polarization-resolved photoluminescence measurements were performed to investigate spin conservation d…
Compact Mach-Zehnder acousto-optic modulator
2006
The authors demonstrate a compact optical waveguide modulator based on a Mach-Zehnder interferometer driven by surface acoustic waves. The modulator was monolithically fabricated on GaAs with an active region length of approximately 15μm. It yields peak-to-peak modulation exceeding 90% of the average transmission and operation in the gigahertz frequency range.
Acousto-optic interaction in biconical tapered fibers: shaping of the stopbands
2016
The effect of a gradual reduction of the fiber diameter on the acousto-optic (AO) interaction is reported. The experimental and theoretical study of the intermodal coupling induced by a flexural acoustic wave in a biconical tapered fiber shows that it is possible to shape the transmission spectrum, for example, substantially broadening the bandwidth of the resonant couplings. The geometry of the taper transitions can be regarded as an extra degree of freedom to design the AO devices. Optical bandwidths above 45 nm are reported in a tapered fiber with a gradual reduction of the fiber down to 70 μm diameter. The effect of including long taper transition is also reported in a double-tapered st…
Tunable coupled surface acoustic cavities
2012
We demonstrate the electric tuning of the acoustic field in acoustic microcavities (MCs) defined by a periodic arrangement of metal stripes within a surface acoustic delay line on LiNbO3 substrate. Interferometric measurements show the enhancement of the acoustic field distribution within a single MC, the presence of a “bonding” and “anti-bonding” modes for two strongly coupled MCs, as well as the positive dispersion of the “mini-bands” formed by five coupled MCs. The frequency and amplitude of the resonances can be controlled by the potential applied to the metal stripes.
Acousto-optical multiple interference switches
2007
The authors introduce an alternative approach for acousto-optical light control based on the interference of light propagating through several waveguides, each subjected to a periodic refractive index modulation induced by a surface acoustic wave. The feasibility of the concept is demonstrated by the realization of an optical switch for arbitrary time intervals with an on/off contrast ratio of 20.
Acousto-optical multiple interference devices
2008
We present a new concept for waveguide acousto-optical devices based on coupled MachZehnder interferometers driven by acoustic waves. These acousto-optical multiple interference devices use the periodic refractive index modulation induced by the acoustic wave to realize functionalities such as ON/OFF switching for an arbitrary time interval, as well as for efficient light modulation at high harmonics of the acoustic frequency and pulse shaping for, e.g., integrated Q-switches. We also discuss application of the concepts to light modulation by very high acoustic frequencies, where the acoustic wavelengths become much shorter than the optical ones.
Metodología para la mejora acústica de recintos de culto. Aplicación en la Catedral de Valencia
2021
[ES] Los recintos de culto son espacios patrimoniales de gran valor cultural, artístico y arquitectónico. Asimismo, en ellos tienen lugar eventos, integrantes de su patrimonio cultural inmaterial, donde la transmisión del sonido es un factor preferente. Por todo ello, resulta relevante garantizar un adecuado acondicionamiento acústico de los recintos de culto para sus dos usos fundamentales, la música religiosa y la palabra. Para ello, se ha establecido una metodología compuesta por las fases de medición acústica, estudio del comportamiento acústico del recinto, levantamiento y calibración del modelo acústico y simulaciones acústicas. Al tratarse de edificios protegidos, las propuestas de i…
Phonon-induced polariton superlattices
2006
We show that the coherent interaction between microcavity polaritons and externally stimulated acoustic phonons forms a tunable polariton superlattice with a folded energy dispersion determined by the phonon population and wavelength. Under high phonon concentration, the strong confinement of the optical and excitonic polariton components in the phonon potential creates weakly coupled polariton wires with a virtually flat energy dispersion.
Los efectos de la contaminación acústica en la salud: conceptualizaciones del alumnado de Enseñanza Secundaria Obligatoria de Valencia
2010
Este trabajo parte de la hipótesis de que el alumnado de Educación Secundaria Obligatoria no considera la contaminación acústica, como un problema ambiental importante y desconoce sus efectos nocivos para la salud. A pesar de la importancia del ruido como contaminante ambiental en las sociedades modernas y de las consecuencias directas que tiene sobre la salud humana, el alumno de Secundaria no adopta una postura crítica al respecto, ni en los institutos, como parte fundamental del sistema educativo, ni en la sociedad como agente activo del futuro. This paper departs from the hypothesis that raises that the students of Secondary Obligatory Education do not consider the acoustic pollution to…