Generation of Ultrasound Based on the Frequency Response Characteristics of the “Koss Pro Headphone” with R. David Case Sound Wave Files’—A Case Study

The research aim of this work is to analyse the characteristics of R. David Case Sound waves that are posited to have positive effects on people suffering from tinnitus. Moreover, the participants who listened to these sound wave files using specific headsets or headphones of the Koss models (ktx Pro, ksc-75) showed improved health condition such as alleviating tinnitus that they are suffering from. Therefore, these discoveries have encouraged R. David Case to pursue positively his journey into finding out what is special about those sounds when being listened specifically with Koss models. In this research, we focus mainly on the technical aspects of R. David Case sound signals which he has recorded. These specific sound waves were analysed using time domain, frequency domain as well as the effect of using the Koss Pro headphone frequency response characteristics applied to the sound. Results obtained from the analysis demonstrated that the generation of ultrasound can be the underlying reason for the treatment of the tinnitus.

Experimental Investigation of Second Interface Cement Bond Evaluation

Cement bond model wells （1：10 scaled-down） were made with a gradually degrading cement annulus for cement bond evaluation of the first interface （between the casing and the cement annulus） and the second interface （between the cement annulus and the formation）. Experimental simulation on cement bond logging was carried out with these model wells. The correlation of acoustic waveforms, casing wave energy and flee casing area before and after cement bonding of the second interface was established. The experimental results showed that the arrival of the casing waves had no relationship with the cement bonding of the second interface, but the amplitude of the casing head wave decreased obviously after the second interface was bonded. So, cement bonding of the second interface had little effect on the evaluation of the cement bond quality of the first interface by using casing head wave arrivals. Strong cement annulus waves with early arrivals were observed before the second interface was bonded, while obvious ＂formation waves＂ instead of cement annulus waves were observed after the second interface was bonded.

Assessing Leak Paths in the Cement Sheath of a Cased Borehole by Analysis of Monopole Wavefield Modes

Evaluation of possible leakage pathways of CO_(2) injected into geological formations for storage is essential for successful Carbon Capture and Storage(CCS).A channel in the borehole cement,which secures the borehole casing to the formation,may allow CO_(2) to escape.Risk assessment and remediation decisions about the pres-ence of such channels depend on channel parameters:radial position r from the center of the borehole;channel thickness d;azimuthal positionφof the channel;and az-imuthal extentθof the channel.Current state-of-the-art cement-bond logging technology,which uses only the first arrival at a centralized borehole receiver,can diagnose limited details about CO_(2) leak channels.To accurately characterize the possible leak paths in the cement,we use a 3-dimensional finite-difference method to investigate the use of the abundant data collected by a modernized monopole sonic tool that contains an array of azimuthally distributed receivers.We also investigate how to improve the tool design to acquire even more useful information.For cases where borehole fluid is either water or supercritical CO_(2),we investigate various receiver geometries,multi-modal analyses of multi-frequency data to discover the type of logging tool that provides the best information for CCS management.We find that an appropriate choice of wave modes,source frequencies,source polarities,and receiver locations and off-sets provides sensitivity to d,φ,θ.The amplitude of the first arrival from a monopole source is sensitive toθ.Amplitudes at receivers at different azimuths are sensitive toφ.The slow Stoneley mode(ST2)velocity is sensitive to d,but ST2 is not easy to pick whenθand d are small.Further improvement is necessary to provide comprehensive information about possible flow channels in casing cement.

Characteristics of wave amplitude and currents in South China Sea induced by a virtual extreme tsunami

This paper investigates the potential extreme tsunami hazards of the worst case scenario of the magnitude M_w=9.30 in South China Sea（SCS）as the Manila Trench is becoming one of the most hazardous tsunami source regions.Using nonlinear shallow water equations model,the time series of surface elevation,arrival time,spatial distributions of maximum wave amplitude and velocity distribution are presented.The characteristics of wave and currents are analyzed.The numerical results indicate that most of the energy of tsunami wave distributes in central and north part of SCS.The offshore regions around SCS will be influenced significantly by the tsunami currents generated by an earthquake in the Manila subduction zone.The maximum wave amplitude near Guangdong Province,Hainan Island,and Taiwan Island exceeds 4 m and velocities at the majority of measured locations near coast exceeds 2 m/s.Nested grid with high resolution is used to study the impacts of the tsunami on Hainan Island,Taiwan Island,and Lingding Bay.The regions with high hazard risk due to strong currents are identified.Finally,a fast tsunami warning method in SCS is developed and discussed,which can provide tsunami warning information in 5 min.

The effects of bonding conditions on the propagation of acoustic waves along a cased borehole

Based on the wave equations in cylindrically layered structures and boundary conditions, the frequency equation for axisymmetric guided waves and the expression for sound fields in a cased borehole excited by a monopole or multipole source have been derived. The synthetic full waveforms excited by the monopole and dipole source are simulated using a real axis integration and FFT method. According to the axisymmetric guided wave modes, the synthetic full waveforms and the effects of the interface conditions on the sound field in a cased borehole have been analyzed and studied respectively. Numerical results indicate that it may be difficult to distinguish well bonded, poorly bonded or unbonded intermediate layer between the steel pipe and formation if only using a monopole source or dipole source. To properly estimate the case boundary conditions, a combination of monopole source logging with dipole source logging is suggested.