Reflection Of Sound Waves Research Articles

Validez y confiablidad de un test en línea sobre los fenómenos de reflexión y refracción del sonido

This work presents the results of a validation and reliability process of a conceptual test on reflection and refraction phenomena of sound waves, a process that was carried out online using Knowledge Applied Technologies (TAC). The development of this process was done by using the Classical Test Theory as a theoretical framework and the use of a website for remote implementation. The use of TAC allowed the validation process to be more agile and extended to a larger sample, allowing application in several universities in Mexico, Colombia, Ecuador, and Chile. The obtaining and analysis of data to achieve the validation and reliability of the instrument was given by means of a system designed specifically for this work, which allowed the realization of the necessary statistics to obtain indicators such as difficulty, discrimination and reliability. Obtaining a test that can be applied and resolve online is a novelty in grounds of the Educational Physics.

EVALUATION OF BONE HEALING AFTER APICAL RESECTION BY ULTRASONOGRAPHY

<h3>Background</h3> Apical resection is a reliable method for the treatment of teeth with persistent periapical lesions or in cases where nonsurgical treatment is not successful. Generally, outcome assessment of apical resection is based on 2-D periapical radiographs. Ultrasound imaging is based on reflection of sound waves at the interface between 2 different tissues and is also recognized as the most risk-free imaging modality. <h3>Objective(s)</h3> Our aim was to evaluate healing of bone after apical resection by using ultrasonography. <h3>Study Design</h3> Ethical approval and patient consent were obtained. Three patients with periapical lesions of endodontic origin were examined with cone beam computed tomography (CBCT) and ultrasonography before surgery. ACUSON S 2000 color Doppler ultrasonography unit with 15 MHz intraoperative probe was used to obtain ultrasound images. In all patients, root canal treatment and apical resection surgery were performed. In 1 patient, during apical surgery, bone graft (Creos Greft, Nobel Biocare Services AG, Zurich, Switzerland) and resorbable collagen membrane (Creos xenoprotect, Nobel Biocare Services AG, Zurich, Switzerland) were used. The other cases were left to secondary healing. Three months after apical resection, periapical radiographs and ultrasonographic examination were performed for follow-up assessment. <h3>Results</h3> The resection area was filled with bone, and hyperechogenic bone healing was monitored by ultrasonography in the patient in whom bone graft and membrane were placed. In 1 patient, the resection area was filled with soft tissue, and ultrasound showed an echogenic area surrounded a hyperechogenic bone border. No internal vascularization was detected. In the other patient, ultrasonography showed a well-contoured anechogenic area with no vascularization, and 3 months after apical surgery, the tooth was extracted. <h3>Discussion/Conclusions</h3> Ultrasound imaging can be a useful tool for the monitoring of apical surgery outcomes without ionizing radiation. Further research is essential with inclusion of more patients.

High-frequency ultrasound for diagnosing skin cancer in adults.

Early, accurate detection of all skin cancer types is essential to guide appropriate management and to improve morbidity and survival. Melanoma and squamous cell carcinoma (SCC) are high-risk skin cancers with the potential to metastasise and ultimately lead to death, whereas basal cell carcinoma (BCC) is usually localised, with potential to infiltrate and damage surrounding tissue. Anxiety around missing early curable cases needs to be balanced against inappropriate referral and unnecessary excision of benign lesions. Ultrasound is a non-invasive imaging technique that relies on the measurement of sound wave reflections from the tissues of the body. At lower frequencies, the deeper structures of the body such as the internal organs can be visualised, while high-frequency ultrasound (HFUS) with transducer frequencies of 20 MHz or more has a much lower depth of tissue penetration but produces a higher resolution image of tissues and structures closer to the skin surface. Used in conjunction with clinical and/or dermoscopic examination of suspected skin cancer, HFUS may offer additional diagnostic information compared to other technologies. To assess the diagnostic accuracy of HFUS to assist in the diagnosis of a) cutaneous invasive melanoma and atypical intraepidermal melanocytic variants, b) cutaneous squamous cell carcinoma (cSCC), and c) basal cell carcinoma (BCC) in adults. We undertook a comprehensive search of the following databases from inception up to August 2016: Cochrane Central Register of Controlled Trials; MEDLINE; Embase; CINAHL; CPCI; Zetoc; Science Citation Index; US National Institutes of Health Ongoing Trials Register; NIHR Clinical Research Network Portfolio Database; and the World Health Organization International Clinical Trials Registry Platform. We studied reference lists as well as published systematic review articles. Studies evaluating HFUS (20 MHz or more) in adults with lesions suspicious for melanoma, cSCC or BCC versus a reference standard of histological confirmation or clinical follow-up. Two review authors independently extracted all data using a standardised data extraction and quality assessment form (based on QUADAS-2). Due to scarcity of data and the poor quality of studies, we did not undertake a meta-analysis for this review. For illustrative purposes, we plot estimates of sensitivity and specificity on coupled forest plots. We included six studies, providing 29 datasets: 20 for diagnosis of melanoma (1125 lesions and 242 melanomas) and 9 for diagnosis of BCC (993 lesions and 119 BCCs). We did not identify any data relating to the diagnosis of cSCC.Studies were generally poorly reported, limiting judgements of methodological quality. Half the studies did not set out to establish test accuracy, and all should be considered preliminary evaluations of the potential usefulness of HFUS. There were particularly high concerns for applicability of findings due to selective study populations and data-driven thresholds for test positivity. Studies reporting qualitative assessments of HFUS images excluded up to 22% of lesions (including some melanomas) due to lack of visualisation in the test.Derived sensitivities for qualitative HFUS characteristics were at least 83% (95% CI 75% to 90%) for the detection of melanoma; the combination of three features (lesions appearing hypoechoic, homogenous and well defined) demonstrating 100% sensitivity in two studies (lower limits of the 95% CIs were 94% and 82%), with variable corresponding specificities of 33% (95% CI 20% to 48%) and 73% (95% CI 57% to 85%), respectively. Quantitative measurement of HFUS outputs in two studies enabled decision thresholds to be set to achieve 100% sensitivity; specificities were 93% (95% CI 77% to 99%) and 65% (95% CI 51% to 76%). It was not possible to make summary statements regarding HFUS accuracy for the diagnosis of BCC due to highly variable sensitivities and specificities. Insufficient data are available on the potential value of HFUS in the diagnosis of melanoma or BCC. Given the between-study heterogeneity, unclear to low methodological quality and limited volume of evidence, we cannot draw any implications for practice. The main value of the preliminary studies included may be in providing guidance on the possible components of new diagnostic rules for diagnosis of melanoma or BCC using HFUS that will require future evaluation. A prospective evaluation of HFUS added to visual inspection and dermoscopy alone in a standard healthcare setting, with a clearly defined and representative population of participants, would be required for a full and proper evaluation of accuracy.

Visualizing sound waves with schlieren optics

Using schlieren optics as a tool to see the invisible, we describe a technique of visualizing traveling ultrasonic (28 kHz) sound waves in real time. Suitable for lecture demonstration purposes or as an instructional laboratory experiment, our setup can readily demonstrate the reflection of sound waves from surfaces, diffraction effects around objects, interference, and standing waves. Additionally, the incorporation of color filters provides information such as gradient directions and sound wave phase differences not obtainable with just a white light source. As an example, acoustic standing waves are analyzed.

Fundamental study on the acoustic fields caused by the interference of supersonic jet with a perforated plate

The supersonic jet contains intensive sound sources. It is known that when this jet collides with the perforated plate, a complicated flow field is formed on the plate and a high-amplitude sound is radiated as compared with the case without the perforated plate. Attention is paid to understanding the sound generating mechanism and proposing the measures to alleviate the sound pressure levels. In this study, two types of fundamental model tests have been carried out with a simple combination of a nozzle and a perforated plate. One is acoustic measurement in an anechoic facility. Test results indicated the amplified sound pressure levels in the forward arc of the nozzle. The aperture geometry suggested certain suppression in sound pressure levels in the arc. The other test is an optical visualization with Schlieren photographs. The photographs tried to account for reflection of high-amplitude sound waves on the plate downstream the nozzle.

Determining the stiffness of the equation of state using low T/W dynamical instabilities in differentially rotating stars

We investigate the nature of low T/W dynamical instabilities in various ranges of the stiffness of the equation of state in differentially rotating stars. Here T is the rotational kinetic energy, while W the gravitational binding energy. We analyze these instabilities in both a linear perturbation analysis and a three-dimensional hydrodynamical simulation. An unstable normal mode of a differentially rotating star is detected by solving an eigenvalue problem along the equatorial plane of the star. The physical mechanism of low T/W dynamical instabilities is also qualitatively confirmed by a scattering of sound waves between corotation and the surface caused by the corotation barrier. Therefore, we can draw a picture of existing pulsation modes unstabilized due to an amplified reflection of sound waves from the corotation barrier. The feature in the eigenfrequency and eigenfunction of the unstable mode in the linear analysis roughly agrees with that in the three-dimensional hydrodynamical simulation in Newtonian gravity. Moreover, the nature of the eigenfunction that oscillates between corotation and the surface for an unstable star requires reinterpretation of pulsation modes in differentially rotating stars. Finally, we propose a manner by which to constrain the stiffness of the equation of state by the direct detection of mode decomposed gravitational waveforms.

Reflection and Transmission of Sound Waves through the Layer of Two-fractional Bubbly Liquid

The mathematical model that determines reflection and transmission of sound waves through a medium containing two-fractional bubbly liquid is presented. For the model of media with three layer the wave reflection and transmission coefficients are calculated. The influence of the volume content of bubbles on the investigated coefficients is shown.

Effect of Poisson's loss factor of rubbery material on underwater sound absorption of anechoic coatings

Rubbery coatings embedded with air cavities are commonly used on underwater structures to reduce reflection of incoming sound waves. In this paper, the relationships between Poisson's and modulus loss factors of rubbery materials are theoretically derived, the different effects of the tiny Poisson's loss factor on characterizing the loss factors of shear and longitudinal moduli are revealed. Given complex Young's modulus and dynamic Poisson's ratio, it is found that the shear loss factor has almost invisible variation with the Poisson's loss factor and is very close to the loss factor of Young's modulus, while the longitudinal loss factor almost linearly decreases with the increase of Poisson's loss factor. Then, a finite element (FE) model is used to investigate the effect of the tiny Poisson's loss factor, which is generally neglected in some FE models, on the underwater sound absorption of rubbery coatings. Results show that the tiny Poisson's loss factor has a significant effect on the sound absorption of homogeneous coatings within the concerned frequency range, while it has both frequency- and structure-dependent influence on the sound absorption of inhomogeneous coatings with embedded air cavities. Given the material parameters and cavity dimensions, more obvious effect can be observed for the rubbery coating with a larger lattice constant and/or a thicker cover layer.

Non-destructive testing of full-length bonded rock bolts based on HHT signal analysis

Full-length bonded rock bolts are commonly used in mining, tunneling and slope engineering because of their simple design and resistance to corrosion. However, the length of a rock bolt and grouting quality do not often meet the required design standards in practice because of the concealment and complexity of bolt construction. Non-destructive testing is preferred when testing a rock bolt's quality because of the convenience, low cost and wide detection range. In this paper, a signal analysis method for the non-destructive sound wave testing of full-length bonded rock bolts is presented, which is based on the Hilbert-Huang transform (HHT). First, we introduce the HHT analysis method to calculate the bolt length and identify defect locations based on sound wave reflection test signals, which includes decomposing the test signal via empirical mode decomposition (EMD), selecting the intrinsic mode functions (IMF) using the Pearson Correlation Index (PCI) and calculating the instantaneous phase and frequency via the Hilbert transform (HT). Second, six model tests are conducted using different grouting defects and bolt protruding lengths to verify the effectiveness of the HHT analysis method. Lastly, the influence of the bolt protruding length on the test signal, identification of multiple reflections from defects, bolt end and protruding end, and mode mixing from EMD are discussed. The HHT analysis method can identify the bolt length and grouting defect locations from signals that contain noise at multiple reflected interfaces. The reflection from the long protruding end creates an irregular test signal with many frequency peaks on the spectrum. The reflections from defects barely change the original signal because they are low energy, which cannot be adequately resolved using existing methods. The HHT analysis method can identify reflections from the long protruding end of the bolt and multiple reflections from grouting defects based on mutations in the instantaneous frequency, which makes weak reflections more noticeable. The mode mixing phenomenon is observed in several tests, but this does not markedly affect the identification results due to the simple medium in bolt tests. The mode mixing can be reduced by ensemble EMD (EEMD) or complete ensemble EMD with adaptive noise (CEEMDAN), which are powerful tools to used analyze the test signal in a complex medium and may play an important role in future studies. The HHT bolt signal analysis method is a self-adaptive and automatic process, which can be programed as analysis software and will make bolt tests more convenient in practice.

Расчет коэффициента отражения концевого отверстия канала без фланца в акустических проектах

The computational error analysis for coefficient of reflection of plane sound waves at the end of opening channel without flange performed by means of formulas commonly used in practice has demonstrated their unacceptability for accurate acoustic calculations, and limitations of the Helmholtz numbers’ range, where these formulas are applicable. In this work have been proposed calculated dependences, convenient for practical usage and enabling more accurately calculate by computer approach the considered quantity’s values in a whole range of existence of the plane waves in the channel.

Sources of measurement uncertainty in determination of the directional diffusion coefficient value

Values of the directional sound diffusion coefficient, according to recommendations of ISO 17497-2 standard, are measured in the free field of an anechoic chamber. The procedure proposed in the standard for determination of directivity patterns characterizing reflection of sound wave from an examined structure is biased by a measurement uncertainty following from the effect of individual elements of the measurement chain and operations performed on the recorded signal. Further sources of uncertainty can be related to the sample itself due to possible imperfections of workmanship.The paper presents an analysis of possible sources of the measurement uncertainty encountered when the directional sound diffusion coefficient is determined and an attempt to evaluate the effect of individual sources on the expanded uncertainty of the measured parameter. Using the Fraunhofer approach to the wave equation and the Monte Carlo method, the effect of the measurement angular resolution, microphone and sample position, repeatability of generated and recorded signals, the signal-to-noise ratio, and precision of sample workmanship on uncertainty of the directional sound diffusion coefficient was determined. For the value of 0.025 adopted as the admissible maximum of the expanded uncertainty of the parameter, maximum allowable values for uncertainties of individual input parameters were identified.

Transmission and reflection of sound wave from a layer of liquid with gas bubbles

The problem of reflection and transmission of sound wave through the two-layer medium containing a layer of bubble liquid is considered. A comparison of the reflection and transmission of wave coefficients with known experimental data is presented.

Doppler Comparative Measurements in the Reconstruction of Limbs with Flaps and Grafts

Abstract Doppler technique was first described by the Australian physicist and mathematician Christian Doppler. Doppler effect is defined as a reflection of high frequency sound waves of different frequency when they come in contact with the movable structure in the blood vessel. Waves that go to transducers are coded red, while waves that move away from the transducer are coded blue. Doppler main types can be classified as following: continuous wave (CW) Doppler, spectral Doppler, color Doppler and Power Doppler color. The study was realizedat the University Clinic for Plastic and Reconstructive Surgery. It is a randomized prospective study. During the study two groups of 30 patientseach were formed. Each patient was required a permission for reconstructive surgery procedure and an informed consent for participation in the study. For all patients a specially designed questionnaire (non-standardized) was filled out. 1. First (I) group of patients treated with flaps. In this group a type of reconstructive technique with skin or complex flapshas been applied. 2. Second group (II) of patients treated with grafts (split thickness grafts). In this group applied reconstruction comprised application of skin grafts with partial thickness. The study included patients with defects of the skin and soft tissues, whohad an indication for reconstructive surgery procedure. Exclusion criteria of patients for participation in the study were: children under 14 years of age, adults over 75 years, people with systemic diseases that can affect the results of reconstructive intervenetions and patients who have without periosteum bone-like surface defect as contraindication for skin grafting. The results of the reconstructive procedures according to the objectives set were investigated clinically into three time periods: preoperative, postoperative day 7 and day 30 postoperatively. The following investigations were carried out: determination of the circulation levels by means of Doppler; determination of the levels of limbs circulation is distal to the site of reconstruction in the pre-and postoperative period (day 7 and day 30); For the evaluation of blood flow the following parameters were used: • PSV-Peak systolic velocity • PI - Pulsatility index RI - Resistance indexPI and RI were calculated using the formula: • PI = PSV - EDV / Vmean • RI = PSV - EDV / PSV EDV indicates the flow velocity in late diastole and V mean, the average speed of blood flow through the artery. By assessment of arterial status before and after surgery through the analysis ofvascular waves at different locations of the vascular tree of the upper and lower extremities, we registered significant difference between the two examined groups, which speaks in favor of the use of flaps in reconstruction of the lower limbs.

교과서와 교사용 지도서에 제시된 소리의 성질 단원의 파동개념에 대한 초등 교사들의 이해도, 확신도와 친숙도 분석

The purpose of this study was to analyze elementary school teachers' understanding, certainty, and familiarity with 13 key concepts of wave physics that are presented in textbook and teacher's guidebook. 123 elementary school teachers answered concept tests and questionnaires. In the results to these tests and questionnaires, teachers demonstrated a high level of understanding and high certainty in understanding with regard to the concepts of sound generation, effect of medium on wave, timbre, wavelength, and trough and crest of wave. For the topics of sound velocity, wave reflection and wave transmission, teachers demonstrated a high level of understanding but low certainty in understanding. With regard to sound propagation, teachers demonstrated a low level of understanding and an improperly high certainty in that low understanding. Teachers lacked knowledge, i.e., displayed a low level of understanding and low certainty in sound strength, sound frequency, constructive interference and destructive interference. In constructive and destructive interference, the teachers also displayed a low level of familiarity. We analyzed the differences in teacher's understanding, certainty, and familiarity according to teacher demographics defined by the teacher's gender, teaching experience with concepts of sound, career, curriculum track while in high school, and major in university. There were no significant differences in understanding, certainty, or familiarity as defined by gender, teaching experience, and career. However, these displays of knowledge were affected by the teacher's curriculum track in high school and their major. These results suggest that the teacher's understanding of, familiarity with, and certainty in wave physics concepts are more influenced by their learning experience than by their teaching experience. Therefore, we suggest additional learning opportunities for teachers (such as teacher training programs) in order to improve teacher knowledge and correct teacher misconceptions in wave physics.

Characteristics of space charge distribution in epoxy-paper composite insulation system

The HVDC dry-type bushing, with its main insulating medium being epoxyimpregnated- paper composite, is a key device in the ultra-high voltage direct current power transmission system. The HVDC bushing is under the combined effect of electricity, heat, and mechanical stress when it is in operation, in which case the electric field strength in the core of bushing is high, the temperature in the central conductor is high, and the interfacial effect between the epoxy layer and insulating paper is strong. Consequently, space charge will accumulate in the epoxy-paper composite insulation. Previous studies mainly focuses on the characteristics of space charge distribution in polymer-micro-nano filler, whereas the studies on that in epoxy-insulating-paper composite are quite limited. This paper, based on the HVDC bushing made up of epoxy-insulating-paper composite, establishes and a space charge measuring system which is suitable for the pulse electro-acoustic (PEA) method at high temperature (⩽110 °C). A modified PEA method which is applicable to the measurement of space charge in the multi-dielectric-layer composite with different acoustic impedance is put forward. By controlling the thicknesses of dielectric layers in the composite sample, the effect of sound wave reflection on the measuring system can be eliminated. An in-depth study is conducted on the effects of temperature and field strength on the characteristics of space charge distribution in epoxy-paper composite.

Enhanced Soundproof Performance of Construction Coatings Using Polyvinyl Acetate Resin and Calcium Sulfate Whiskers

AbstractThis study reports an enhanced soundproof performance of polyvinyl acetate (PVA)-based coating by adding high-aspect-ratio calcium sulfate whiskers. One efficient microwave-assisted (MA) method is adopted to synthesize CaSO4 whiskers with a high aspect ratio of 40–80. The two-step MA method is capable of forming highly crystalline CaSO4·2H2O crystals at 85°C, demonstrated by X-ray diffraction analysis. This work uses an anechoic termination method to analyze the sound transmission loss (TL) of PVA-based coatings. The TL of CaSO4/PVA composite coating shows an increased trend with the amount of CaSO4 whiskers within the frequency region of 400–3,600 Hz. The improved TL can be attributed to the fact that an air pocket is contained in the CaSO4 stacking layer, imparting the reflection and refraction during the sound wave transmission in the composite coating. The energy of incident sound waves is weakened by consecutive reflection, scattering, refraction, and diffraction of sound waves in the CaSO4/P...

The Reliability of Oral and Pharyngeal Dimensions Captured with Acoustic Pharyngometry.

Acoustic Pharyngometry (APh) is a method for quantifying oropharyngeal tract configuration using sound wave reflection and is commonly used in diagnostics and research of sleep apnea. The standard preset output of APh (minimal cross-sectional area) has been established as reliable. However, by conducting post-processing measures on specific breathing tasks, APh data can also reveal oral length, oral volume, pharyngeal length, and pharyngeal volume. Given that these measures may have utility in dysphagia research, the reliability of these measures is unknown and is the focus of the current study. Ten young healthy female volunteers completed two sessions of APh data collection to obtain measures of oral length, oral volume, pharyngeal length, and pharyngeal volume 1week apart. Two-way mixed intraclass correlation coefficients were calculated to establish intra-rater reliability, inter-rater reliability, and test-retest reliability. Results revealed excellent levels of agreement within and across raters for all oropharyngeal tract parameters. Levels of test-retest agreement for oral length and oral volume indicated these parameters are appropriate for monitoring change within an individual. All parameters were deemed to have acceptable test-retest values as outcome measures in group-level analysis.

Relative contributions of various modes of acoustic radiation force to creating mechanical stress in soft tissues

There are several physical effects responsible for the generation of acoustic radiation force (ARF) in soft tissue. The first effect, which is widely used in elastographic applications of ARF, is the transfer of momentum from ultrasonic wave in an attenuating medium due to absorption and scattering. Two other effects include reflection of sound wave from the boundaries between tissues differing in the acoustic impedance and second, spatial variations of the energy density of the propagating wave as a result of variations in the sound wave velocity in a medium. The latter mode of ARF can be directed both outward and toward the source of the propagating wave. In this study, relative contributions of various modes of acoustic radiation force are investigated both theoretically and experimentally. Using Green function for the acoustic potential near the boundaries between tissue structures, the expression for the motion of tissue interfaces under the action of short ultrasonic pulses is derived. Theoretical estimates of dynamics of the soft tissue response to various modes ARF induced by the microsecond range ultrasonic pulses are in agreement with experimental data. Findings of this study may serve as the basis of new approaches in soft tissue elastography.

Light-weight poly(vinyl chloride)-based soundproofing composites with foam/film alternating multilayered structure

Poly(vinyl chloride)-based (PVC) multilayered composites with alternating foam and film layer structure were designed through a multilayered co-extrusion system. Light-weight composites with good soundproofing properties were obtained. The effects of foaming process, acoustic impedance mismatch, and layer number on the soundproofing properties were investigated. Sound transmission loss (STL) was used to characterize the soundproofing properties. The experimental results revealed that the foam/film multilayered composites showed higher STL and lower density than the film/film multilayered composite without foaming process. In addition, the multilayered composite presented better soundproofing properties when there was a bigger acoustic impedance mismatch between adjacent layers. Moreover, as the layer number increased from 2 to 16, the STL of the PVC composite increased gradually and reached a maximum at 8 layers (an average value of 26.3dB). However, the STL of 16-layer composite decreased because of the reduction of scattering and reflection of sound waves among the bubbles.

Smoothed particle hydrodynamics simulation of sound reflection and transmission

Mesh-based methods are widely used in acoustic simulations nowadays. However, acoustic problems with complicated domain topologies and multiphase systems are difficult to be described with these methods. On the contrary, Smoothed Particle Hydrodynamics (SPH), as a Lagrangian method, does not have much trouble in solving these problems. The present paper aims to simulate the reflection and transmission of sound waves with the SPH method in time domain. Firstly, the linearized acoustic equations are represented in the SPH form by using the particle approximation. Then, one dimensional sound reflection and transmission are simulated with the SPH method and the solutions are compared with the theoretical results. Finally, the effects of smoothing length and neighboring particle numbers on the computation are discussed. The errors of sound pressure, particle velocity, and change of density show that the SPH method is feasible in simulating the reflection and transmission of sound waves. Meanwhile, the relationship between the characteristic impedance and the reflected waves obtained by the SPH simulation is consistent with the theoretical result.