On the area-averaged effective sound absorption coefficient of porous materials excited by a monopole.

The area-averaged effective sound absorption coefficient (SAC) of a rigid-backed homogeneous porous material subjected to a monopole excitation is calculated as the absorbed-to-incident sound power ratio. Using Allard's model to describe the sound propagation above the porous material, an analytical model for this power-based SAC is proposed and proves to give a good approximation of the sound absorption performance under monopole excitation of sufficiently large areas of material. The impact of factors on the power-based SAC, such as monopole height, material radial dimension used to calculate the sound powers, and material properties is discussed. The power-based SAC frequency-dependent behavior is analyzed through sound intensity field assessments at the material surface and is compared to normal incident plane wave and diffuse field SACs. The sound absorption behavior of sound absorbers under monopole excitation exhibits notable distinctions and peculiar results compared to those observed under plane wave and diffuse fields, particularly at low frequencies and for sources close to the material.

Series and parallel coupling of 3D printed micro-perforated panels and coiled quarter wavelength tubes.

Micro-perforated panel sound absorbers are widely used in noise control applications in the fields of architectural acoustics and transport acoustics. Combining micro-perforated panels with other resonant or sound absorbing systems may broaden the frequency range in which they absorb sound while ensuring that large sound absorption values are reached. In this work, a hybrid sound absorber that combines a micro-perforated panel and a coiled quarter wavelength tube is proposed. Series and parallel configurations of these two systems are studied from analytical, numerical, and experimental point of views. A comparison of two three-dimensional (3D) printing techniques for the production of samples highlights the main challenges for the practical implementation of the proposed design. The advantages and limitations of series and parallel arrangements are discussed and while the parallel configuration is more complex to setup in practice, it provides an improved sound-absorbing performance compared with the series configuration. Finally, the reproducibility of the hybrid absorber in parallel configuration is confirmed by testing samples that were produced with two different 3D printers and in two different laboratories.

Comparison of three full-field optical measurement techniques applied to vibration analysis.

Digital image correlation, deflectometry and digital holography are some of the full-field optical measurement techniques that have matured in recent years. Their use in vibroacoustic applications is gaining attention and there is a need for cataloging their performance in order to provide, to a broad community of users and potential future users, quantitative and qualitative evaluations of these three approaches. This paper presents an experimental comparison of the three optical methods in the context of vibration measurements, along with classical reference measurements provided by an accelerometer and a laser Doppler vibrometer. The study is carried out on two mechanical structures exhibiting various vibration responses when submitted to an impact.

Inter and intra-observer agreement of arterial wall contrast-enhanced ultrasonography in giant cell arteritis.

Objective: The aim of this study was to analyze inter- and intra-observer agreement for contrast-enhanced ultrasonography (CEUS) for monitoring disease activity in Giant Cell Arteritis (GCA) in the wall of axillary arteries, and common carotid arteries. Methods: Giant cell arteritis patients have CEUS of axillary arteries and common carotid. These images were rated by seven vascular medicine physicians from four hospitals who were experienced in duplex ultrasonography of GCA patients. Two weeks later, observers again rated the same images. GCA patients were recruited in from December 2019 to February 2021. An analysis of the contrast of the ultrasound images with a gradation in three classes (grade 0, 1, and 2) was performed. Grade 0 corresponds to no contrast, grade 1 to moderate wall contrast and grade 2 to intense contrast. A new analysis in 2 classes: positive or negative wall contrast; was then performed on new series of images. Results: Sixty arterial segments were evaluated in 30 patients. For the three-class scale, intra-rater agreement was substantial: κ 0.70; inter-rater agreement was fair: κ from 0.22 to 0.27. Thirty-four videos had a wall thickness of less than 2 mm and 26 videos had a wall thickness greater than 2 mm. For walls with a thickness lower than 2 mm: intra-rater agreement was substantial: κ 0.69; inter-rater agreement was fair: κ 0.35. For walls with a thickness of 2 mm or more: intra-rater agreement was substantial: κ 0.53; inter-rater agreement was fair: κ 0.25. For analysis of parietal contrast uptake in two classes: inter-rater agreement was fair to moderate: κ from 0.35 to 0.41; and for walls with a thickness of 2 mm or more: inter-rater agreement was fair to substantial κ from 0.22 to 0.63. Conclusion: The visual analysis of contrast uptake in the wall of the axillary and common carotid arteries showed good intra-rater agreement in GCA patients. The inter-rater agreement was low, especially when contrast was analyzed in three classes. The inter-rater agreement for the analysis in two classes was also low. The inter-rater agreement was higher in two-class analysis for walls of 2 mm thickness or more.

An illustrated tutorial for logarithmic scales and decibels in acoustics.

Acoustics is generally defined as the science that deals with the production, transmission, and reception of sound and the understanding and control of its effects. In fact, the fields of acoustics cover an especially broad range of subjects and domains, and comprehensive acoustics textbooks are usually quite thick as a consequence. While they are valuable resources for researchers, these books might appear a little daunting for a young audience or for people who are new to acoustics. This paper is an example of how educational comics can be designed and used to introduce one of the most commonly discussed topics when the basics of acoustics are taught: decibel level. Seven drawn pages constitute a visual support to explain the origin and history of the decibel, together with examples from acoustics and other domains on the use of logarithmic scales and classical decibel calculations. Several comments and comprehensive bibliographical references are also provided for each drawn page to enlarge the range of subjects or exercises that can be discussed in courses and foster further readings.

Explaining and teaching acoustics through comics, interactive web pages, and video games.

Comics and manga have long been seen as childish literature, even if sometimes referred to as an art. Webpages discussing matters like Mathematics or Science are usually considered popularized content and not as tools with which research can be built. Arcade video games are often not considered serious games that can be used for learning or team building purposes. In this work, we present examples of comics, interactive web pages, and arcade video games that can be used to learn the basics of vibro-acoustics or to focus on more specific topics such as the acoustics of porous media. The reader can experience most of these visual narrative examples following the provided links. An objective of this collection is to make them better known and to stimulate further initiatives on these topics in acoustics education. To this effect, recommendations from various use cases of these visual narratives for different levels of education are also given.

Pharmaco-mechanical catheter-directed thrombolysis versus recanalization and stenting for post thrombotic syndrome after lower limb deep vein thrombosis: a comparative study.

Background: Endovenous interventional procedures can be used in addition to therapeutic anticoagulation to treat deep vein thrombosis in selected patients with proximal vein involvement (vena cava, iliac and/or common femoral). The aim of this study was to compare venous patency and the post-thrombotic syndrome (PTS) in patients treated with pharmaco-mechanical catheter-directed thrombolysis (PMT) versus recanalization-stenting for PTS after a proximal lower limb deep vein thrombosis. Methods: Between January 2014 and December 2020, this retrospective and monocentric study included patients with very symptomatic acute iliofemoral deep vein thrombosis treated with PMT within 21 days after diagnosis (PMT group) and patients with PTS caused by chronic venous obstruction treated with recanalization and stenting (CRS group). Results: A total of 116 patients were included (26 PMT, 90 CRS). The rate of primary patency was 81.8% (18/22 patients) in the PMT group and 78.4% (69/88) in the CRS group (P>0.99). The rate of venous patency at the last follow-up was 76.9% (20/26) in the PMT group and 82.2% (74/90) in the CRS group (P=0.57). The median number of stents was 2 (range, 0-5) in the PMT group and 3 (range, 0-7) in the CRS group (P<0.001). The median stent length was 150 mm (range, 60-390 mm) and 280 mm (range, 120-820 mm), respectively (P<0.001). The median last Villalta score was 2 (range, 0-10) in the PMT group and 2 (range, 0-21) in the CRS group (P=0.55). The rate of venous claudication at the last follow-up was 19.0% (4/21) in the PMT group and 12.0% (10/83) in the CRS group (P=0.47). Conclusions: In this study, there was no difference in venous patency and in the rate and severity of PTS between the PMT and CRS groups. The number of stent and their length were significantly lower in the PMT group compared with the CRS group.

Recording of bruxism events in sleeping humans at home with a smart instrumented splint.

Objective: The aim of this paper is to report quantitative and qualitative characteristics of bruxism events recorded in sleeping humans with a new smart ambulatory system specifically designed to measure dental clenching and grinding forces. The device is wireless and rechargeable, which enables its use over extended periods.Methods: Thirty recordings were obtained from volunteer subjects who wore the device at home during 10 consecutive nights (Clinicaltrials.gov N° NCT03363204).Results: The recordings showed that the system was able to successfully monitor bruxism during 10 consecutive nights, allowing a quantitative (number, duration, intensity, distribution during the night), as well as a qualitative characterization of the bruxism events (clenching vs. grinding).Discussion: This system could offer new perspectives in the field of bruxism, either as a research tool for clinical studies or as a medical device for the ambulatory home-based monitoring of bruxism.

[Orthognathic surgery and joint dysfunctions: benefits or risks?] / Chirurgie orthognathique et dysfonctionnements articulaires : bénéfices ou risques ?

INTRODUCTION: The aim of this article was to present a synthesis of recent bibliographic data concerning the relationship between orthognathic surgery and temporomandibular disorders (TMD). Materials et Methods: A search of relevant articles published over the past ten years (2010-2020) was performed in PubMed using the keywords « orthognathic surgery ¼ and « temporomandibular disorders ¼: 31 articles were included in the review. The data were classified in three main chapters: (1) the effects of orthognathic surgery on TMD, (2) the consequences of orthognathic surgery on the condylar position and (3) the musculo-articular complications of the orthognathic surgery. RESULTS: The results of clinical studies show that the effects of orthognathic surgery on TMD are variable and difficult to predict, so that orthognathic surgery cannot be considered a reliable therapy for joint dysfunctions. DISCUSSION: This review also sheds light on new aspects emerging from recent publications, such as the influence of bruxism, oral dysfunctions and psychological factors and the problem of condyle positioning with the development of techniques for modeling the stresses exerted on the condyle by the finite element method. CONCLUSION: The risk factors for articular complications are poorly known. Female gender, skeletal class II, hyperdivergent profile, rigid osteosynthesis are often reported, but the most factor is the significant preexistence of a joint dysfunction (discal displacement in particular), which argues in favor of a systematic articular pre-operative evaluation including MRI of the temporomandibular joint.

Improving sound transmission loss at ring frequency of a curved panel using tunable 3D-printed small-scale resonators.

An important dip in the sound transmission loss of curved panels occurs at the ring frequency. The relevance of using small-scale resonators to solve this issue is experimentally demonstrated on an aircraft sidewall panel. The effect of varying the spatial distribution of single frequency resonators (including combination with a broadband soundproofing treatment), as well as using multi-frequency resonators with a fixed spatial distribution is studied. Large improvement of the measured sound transmission loss under a diffuse acoustic field excitation is obtained around the ring frequency with limited added mass and very small alteration of the overall sound insulation performance.

Time domain imaging of extended transient noise sources using phase coherence.

An acoustic imaging algorithm is proposed herein for transient noise source time reconstruction. Time domain formulations are not well suited for acoustic imaging because of the size of the resulting system to be inversed. Based on the phase coherence principle widely used in ultrasound imaging and image processing, the first step of the algorithm consists in proposing the phase coherence metric used to reject pixels that are unlikely to contribute to the radiated sound field. This translates in a reduction of the domain size and ill-posedness of the problem. In the second step, the inverse problem is solved using the Tikhonov regularization and the generalized cross-validation to extract the vibration field on the imaging domain. Two test cases are considered: a simulated baffled piston and a panel submitted to a mechanical impact in anechoic conditions. The actual vibration field of the panel is measured with an optical technique for reference. In both numerical and experimental cases, the reconstructed vibration field using the proposed approach compares well with their respective reference. The results confirm that transient excitations can be localized and quantified with the proposed approach, in contrast with the classical time-domain beamforming that dramatically overestimates its magnitude.

Experimental prediction of the vibration response of panels under a turbulent boundary layer excitation from sensitivity functions.

This study aims at validating an experimental method for characterizing the vibration behavior of panels excited by a turbulent boundary layer (TBL) excitation as a possible alternative to standard means like wind tunnels or in situ tests. The approach takes advantage of an explicit separation of the excitation contribution from the dynamic behavior of the panel. Based on the measurement of deterministic transfer functions on the panel, called "sensitivity functions," which are then combined with either measurements or a model of the wall-pressure fluctuations induced by the TBL excitation, the vibration response under such an excitation can be retrieved. For validation purposes, the wall-pressure fluctuations of the turbulent flow generated in an anechoic wind tunnel are measured with a flush-mounted microphone array. The decay rates and the convection velocity, which mainly characterize the excitation, are extracted from these measurements. The plate velocity response to this excitation is estimated following the proposed method using the measured sensitivity functions and the model of Mellen fed with experimentally estimated decay rates and convection velocity. A comparison between a directly measured vibration auto-spectrum under the actual flow and the one predicted following the suggested method shows satisfactory agreement.

Vibroacoustic response of panels under diffuse acoustic field excitation from sensitivity functions and reciprocity principles.

This paper aims at developing an experimental method to characterize the vibroacoustic response of a panel to a diffuse acoustic field (DAF) excitation with a different laboratory setup than those used in standards (i.e., coupled rooms). The proposed methodology is based on a theoretical model of the DAF and on the measurement of the panel's sensitivity functions, which characterize its vibroacoustic response to wall plane waves. These functions can be estimated experimentally using variations of the reciprocity principle, which are described in the present paper. These principles can either be applied for characterizing the structural response by exciting the panel with a normal force at the point of interest or for characterizing the acoustic response (radiated pressure, acoustic intensity) by exciting the panel with a monopole and a dipole source. For both applications, the validity of the proposed approach is numerically and experimentally verified on a test case composed of a baffled simply supported plate. An implementation for estimating the sound transmission loss of the plate is finally proposed. The results are discussed and compared with measurements performed in a coupled anechoic-reverberant room facility following standards.

Estimating transmission loss in coupled reverberant-anechoic rooms by measuring sound intensity with and without a test specimen.

A method for estimating the sound transmission loss of partitions in coupled reverberant-anechoic rooms is proposed, using two sound intensity measurements made before and after a test specimen is installed between the two rooms. Laboratory tests performed following a standard procedure and the suggested method with three different panels provide comparable transmission loss values.

Experimental evidence of modal wavenumber relation to zeros in the wavenumber spectrum of a simply supported plate.

The modal wavenumber of rectangular, simply supported, isotropic thin plates was theoretically shown to be related to the zeros in the wavenumber spectrum and not to the peaks, resulting in an error between the actual modal wavenumber and location of the wavenumber spectrum peak for low mode orders. This theoretical proof is confirmed by experimental results reported in this letter.

Measurement of the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field.

This letter proposes an experimental method to estimate the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field in free-field conditions. Comparisons are made between experiments conducted with this approach, the standard reverberant room method, and numerical simulations using the transfer matrix method. With a simple experimental setup and smaller samples than those required by standards, the results obtained with the proposed approach do not exhibit non-physical trends of the reverberant room method and provide absorption coefficients in good agreement with those obtained by simulations for a laterally infinite material.

Experimental vibroacoustic testing of plane panels using synthesized random pressure fields.

The experimental reproduction of random pressure fields on a plane panel and corresponding induced vibrations is studied. An open-loop reproduction strategy is proposed that uses the synthetic array concept, for which a small array element is moved to create a large array by post-processing. Three possible approaches are suggested to define the complex amplitudes to be imposed to the reproduction sources distributed on a virtual plane facing the panel to be tested. Using a single acoustic monopole, a scanning laser vibrometer and a baffled simply supported aluminum panel, experimental vibroacoustic indicators such as the Transmission Loss for Diffuse Acoustic Field, high-speed subsonic and supersonic Turbulent Boundary Layer excitations are obtained. Comparisons with simulation results obtained using a commercial software show that the Transmission Loss estimation is possible under both excitations. Moreover and as a complement to frequency domain indicators, the vibroacoustic behavior of the panel can be studied in the wave number domain.

[Does dental class II division 2 predispose to temporomandibular disorders?]. / La classe II division 2 prédispose-t-elle aux désordres temporomandibulaires ?

Because of its anatomical/physiological characteristics, the Class II division 2 (class II, div. 2) is one of the malocclusions considered as a possible risk factor for Temporomandibular disorders (TMD). A literature review was conducted from the electronic databases of Medline and Elsevier Masson, through the year 2010, in order to clarify the relationships that may exist between Class II division 2 and TMD. This research helped identify 50 articles: 7 articles specifically concerned the Class II div. 2, 37 articles concerned some of the characteristics of the Class II div. 2, considered individually (Class II, deep bite, retroclined maxillary incisors, mandibular retrognathism) and 6 articles orthodontic treatment. From the conclusions of these studies, the Class II, div. 2 does not appear to represent a significant risk factor for TMD. The clearest association would involve mandibular retrognathism and the risk of articular disk displacement. However, given the low number of articles published on this topic, the methodological variability and the contradictory results, it is difficult to identify reliable conclusions and, consequently, the therapeutic indications for the treatment of Class II div. 2 patients with TMD.

Reproduction of random pressure fields based on planar nearfield acoustic holography.

This article discusses an open-loop approach based on planar nearfield acoustic holography (P-NAH) for the reproduction of random pressure fields, mainly intended for the measurement of vibroacoustic properties of plane panels. The main application is the simulation of turbulent boundary layer excitation in a laboratory environment, as an alternative to in-flight or wind tunnel experiments. The problem under study is the synthesis of random pressure distributions on a plane reproduction surface using acoustic monopoles distributed on a plane source surface facing the reproduction surface. The problem of reproducing a pressure distribution on a plane surface is addressed using the theoretical framework of P-NAH, which is extended to random pressure fields with corresponding imposed cross-spectral density functions. Results of numerical simulations are presented for the reproduction of a diffuse acoustic field, and a subsonic and supersonic turbulent boundary layer. The influence on the reproduction accuracy of the respective sizes of the two planes, their separation and the reproduction source separation are studied. The reproduction approach shows to be effective for the reproduction of diffuse acoustic field and turbulent boundary layer, but with different requirements in terms of plane separation and reproduction sources separation. In the specific case of subsonic turbulent boundary layer and associated sub-wavelength correlation scales reproduction, possible improvements of the method are suggested.

[Course of action in front of children or adolescent suffering from temporomandibular disorders]. / Conduite à tenir chez les enfants ou adolescents présentant des algies et dysfonctionnements de l'appareil manducateur.

Temporomandibular disorders are described in children from the age of 4. Their prevalence and severity increase strongly during the second decade, which corresponds to the period of orthodontic treatments. At this age the most common symptoms are joint clicking sounds (more than 70% of the cases), sometimes accompanied by episodes of intermittent locking. They would be favored by oral parafunctional activities (gum chewing, biting habits, bruxism...), ligamentous hyperlaxity and modification of the intra-articular space relations during growth. The questioning of the patient and his parents and clinical examination (muscular, articular and occlusal) are essential and very often sufficient for establishing the diagnosis. Even more than in the adult, the therapeutic attitude must rely on conservative and non-irreversible methods (explanations, suppression of the parafunctions, occlusal splints in the case of severe bruxism). These considerations are illustrated by the presentation of two representative clinical cases of temporomandibular disorders frequently encountered in children and adolescents.