Acoustic gaps are normally observed in granular inhomogeneous structures made of composite materials. The modulation of the elastic properties in such media creates the coherent effects of scattering and interference that ultimately lead to frequency intervals where sound propagation is forbidden. Contrastingly, we report here an experimental observation of acoustic gaps in homogeneous media; s...

The characteristics of arbitrary amplitude dust ion acoustic solitary waves (DIASWs) are studied in unmagnetized dusty plasmas whose constituents are cold uid ions, nonextensive electrons and stationary negative/positive dust particles. The pseudopotential approach has been used to investigate the structure of localized waves. It is found that, solitary waves exist in a definite interval for th...

This paper is concerned with an improved network model in acoustical application to petroleum logging and seismic exploration. Utilizing acoustic-electric analogue, we report in this paper a newly developed acoustic-logging network model. Important relationships amongst various physical factors are established, i.e. driving-voltage signal, electric-acoustic conversion of source-transducer, acou...

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...

Our recent experiments with Gaussian mixture (GMM) based acoustic models have shown that employing context dependent acoustic models, namely triphones, can greatly improve recognition accuracy [1] in comparison to systems based on context independent units. Significant portion of our research has been aimed at exploring the possibilities of neural networks as acoustic models for speech recognit...

Perforates are for instance used in mufflers for automotive applications and in acoustic liners for aircraft engines. In these applications they are often exposed to high level acoustic excitation in combination with grazing or bias flow. The paper is based on an experimental study of the nonlinear properties of these types of samples without mean grazing or bias flow as well as on a study of a...

A popular phantom in photoacoustic imaging is poly(vinyl alcohol) (PVA) hydrogel fabricated by freezing and thawing (F-T) aqueous solutions of PVA. The material possesses acoustic and optical properties similar to those of tissue. Earlier work characterized PVA gels in small test specimens where temperature distributions during F-T are relatively homogeneous. In this work, in breast-sized sampl...