A Simple Acoustic Sensor Test Platform for Respiratory and Cardiac Acoustical Monitoring

The properties of various acoustic interfaces (stethoscopes) for respiratory monitoring and phonocardiography are compared using a special-purpose custom-built electronic vibration platform that can be driven by an electronic test signal. Sample sensitivity data for various stethoscope designs are presented in this study.

Imaging above an extended-reach horizontal well using converted shear waves and a rig source

We evaluated a method for using 3C vertical seismic profile data to image acoustic interfaces located between the surface source and a downhole receiver array. The approach was based on simple concepts adapted from whole-earth seismology, in which observed compressional and shear wavefields are traced back to a common origin. However, unlike whole-earth and passive seismology, in which physical sources are imaged, we used the observed compressional and shear wavefields to image secondary sources (scatterers) situated between the surface source and the downhole receiver array. The algorithm consisted of the following steps: first, estimating the receiver compressional wavefield; second, using polarization to estimating the shear wavefield; third, deconvolving the shear wavefield using estimates of the source wavelet obtained from the direct compressional wave; fourth, the compressional and shear wavefields were back projected into the volume between the source and receivers; where, finally, an imaging condition was applied. When applied to rig-source VSP data acquired in an extended-reach horizontal well, this process was demonstrated to give images of formation features in the overburden, consistent with surface-seismic images obtained from the same area.

FINITE ELEMENT METHODS FOR STRUCTURAL ACOUSTICS ON MISMATCHED MESHES

In this paper, a new technique is presented for structural acoustic analysis in the case of nonconforming acoustic–solid interface meshes. We first describe a simple method for coupling nonconforming acoustic–acoustic meshes, and then show that a similar approach, together with the coupling operators from conforming analysis, can also be applied to nonconforming structural acoustics. In the case of acoustic–acoustic interfaces, the continuity of acoustic pressure is enforced with a set of linear constraint equations. For structural acoustic interfaces, the same set of linear constraints is used, in conjunction with the weak formulation and the coupling operators that are commonly used in conforming structural acoustics. The constraint equations are subsequently eliminated using a static condensation procedure. We show that our method is equally applicable to time domain, frequency domain, and coupled eigenvalue analysis for structural acoustics. Numerical examples in both the time and frequency domains are presented to verify the methods.