Research on the acoustic correlates of breathiness has been plagued by a lack of consistent findings across studies and low intra- and inter-rater agreement. Sources of variability can arise from different sources including: differences in stimulus types (recorded or synthesized); differences in speaker groups (for recorded stimuli) or in synthesis parameters (for synthesized stimuli); differences in experimental methodologies (task type, number of repetitions, listener backgrounds and experience). This review discussed these sources of variability, and described solutions that have the potential to address the variability and the inconsistencies often reported in the literature. A critical appraisal of the evidence about the relative importance of various acoustic measures resulted in the identification of measures of periodicity, noise content, and high-to-low frequency energy as the most likely acoustic correlates of breathiness.
An analysis method using a spectral collocation method for the vibration of cylindrical shells is proposed. Conventional spectral collocation methods have difficulty applying boundary conditions to fourth-order differential equations such as vibration equations of cylindrical shells. In this paper, an Hermite differentiation matrix is developed such that the proposed spectral collocation method can treat flexibly various boundary conditions. Since the vibration displacement of a cylindrical shell is periodic in the circumferential direction, it is solved semi-analytically using the Fourier series expansion. It is shown that the proposed method can offer more accurate solutions at a smaller number of unknowns, in less computation time and required memory than a finite element method.
In this work, we demonstrate the possibility of focusing a stream of microparticles to generate a matrixlike distribution using bulk acoustic standing waves. To achieve this goal, an axial acoustic excitation was performed on a suspension of spherical quasi-monodisperse microparticles in a flow through minichannel with a square cross section of 2 mm× 2 mm. The pair of transducer elements was also used for stimulation at several frequencies corresponding to its theoretical eigenmodes. The generation of the matrixlike tree-dimensional (3D) structures of focused particles was achieved by reflections of the acoustic radiation force associated with the square geometry. Particle positions were recorded by interferometric digital holographic microscopy, and the corresponding normalized distribution in the cross section was calculated for each experimental setting. The focusing efficiency was investigated through the variation of the acoustic energy density induced by the voltage applied to the piezo part and the injected flow rate. The acoustic field was numerically computed and compared with the experimental positions of particles in the cross section of the channel.
In this study, we observe traveling sound waves with a laser and computed tomography. In our previous research, we observed steady-state sound fields using a sine wave signal. However, transient sound fields observation is necessary in order to observe more complicated sound fields that need to be separated into direct and reflected sounds. Therefore, in this study, we use a traveling sound wave (pulse sound wave). For fundamental experiments, we observed projections of a traveling pulse sound wave generated by a 2-way loudspeaker and a flat-panel loudspeaker with a laser. For transit sound fields, we used the sound field projections obtained with a laser to observe that a flat sound wave generated by a flat-panel loudspeaker is reflected by a sound-reflecting board. Then, we reconstructed the sound field information on the transition of a pulse sound wave generated by a 2-way loudspeaker, by computed tomography.
Field measurements of noise generated from two different wind turbines, one with an upwind rotor and one with a downwind rotor, have been performed. To examine the radiation characteristics of wind turbine noise, some receiving points were set around each wind turbine and the apparent A-weighted sound power levels were calculated from the obtained data at 200 ms intervals under various wind conditions. Wind turbine operational data were collected at 1 s intervals along with corresponding acoustic data. Additionally, a simple empirical formula for the sound directivity was proposed, assuming the directivity pattern of aerodynamic and mechanical sound to be bi- and omnidirectional, respectively. The results showed that the horizontal directivity of the A-weighted sound pressure level at the ground level for the two different wind turbines is almost the same, whereas the frequency dependence of the sound directivity is different for the individual wind turbines. Furthermore, obtaining data of the rotor rotational speed, output power, and nacelle direction is strongly recommended to assess the characteristics of noise emission, such as the changes in the sound power level, sound directivity, and tonal components of wind turbine noise.