We report the modeling and designing aspects of different types of photo-acoustic (PA) cell based on the excitation of longitudinal, radial and azimuthal mode using CW and pulse lasers. The results are obtained by employing fluid dynamics equations along with Bessel’s function. The obtained results based on stimulation of longitudinal, radial and azimuthally resonance modes of the Photo acousti...

An experimental investigation of the acoustical behaviour of a liner in a rectangular channel with grazing flow has been conducted. The liner consists of a ceramic structure of parallel square channels: 1mm by 1 mm in cross section, 65 mm in length, and a surface density of 400 channels/inch square. The channels are rigidly terminated, thus constituting a locally reacting structure. In the abse...

Direct numerical simulations of a turbulent boundary layer over a bump were performed to examine the effects of surface longitudinal curvature on wall pressure fluctuations (pw) and flow induced noise. Turbulence statistics and frequency spectra were obtained to elucidate the response of wall pressure fluctuations to the longitudinal curvature and to the corresponding pressure gradient. Wall pr...

Single crystals of compounds of calcium gallium germanate (CGG) structure with the general formula A3BC3D2O14, have been discussed as promising new materials for acoustic device applications. Since the CGG (or langasite) family belongs to the same acentric crystal class 32 as quartz similar acoustic properties can be expected. In particular, temperature compensated crystal cuts were predicted w...

This article proposes a hybrid numerical-analytical approach to effectively predict the sound absorption coefficient of complex periodic metamaterials with reasonably low computation time. A variation an existing metamaterial, consisting succession necks and cavities, is also proposed. The design was intended decrease frequencies resonant peaks consists in adding eccentricity neck position. com...

An efficient finite volume approach has been used to develop a three dimensional Helmholtz acoustic solver for complex geometries. This acoustic solver was utilized to obtain characteristic mode shapes and frequencies of a baffled combustion chamber. An experimental setup, including stationary and moving sensors, has also been used to measure these quantities for the same model combustion chamb...

biophysical profile (bpp) test is the most commonly used antenatal test of fetal well-being. purpose of this study is determining the influence of acoustic stimulation (as) on bpp testing time. about 55 pregnant women at 35 to 42 weeks who referred to department of obstetric & gynecology at university of medical sciences, tabriz, iran, were selected randomly. we used abdominal ultrasound guidan...