Search Results (277)

This study presents a case-specific joining method for modular, large-scale components manufactured using Selective Laser Sintering (SLS). A T-slot joint reinforced with a pultruded carbon fiber rod was developed to enable the segmental assembly of polymer fan blades that exceed the build volume of common SLS printers. Through an iterative design process, five joint variations were investigated, focusing on the optimization of slot geometry (fillet radii and wall thickness) and the integration of carbon fiber reinforcements to create a high-strength hybrid connection. The experimental findings were validated using a non-linear finite element analysis (FEA) utilizing an iteratively calibrated Young’s modulus of 710 MPa, which accounts for the 50/50 virgin-to-reused PA2200 powder ratio employed in the study. The numerical model identified that the primary sites for crack initiation were the fillet radii of the female slot, where localized equivalent plastic strains reached critical levels of up to 84% in tension and 78% in bending. The final design achieved an average tensile strength of 27.6 MPa, exceeding the design threshold of 21.9 MPa with a safety factor of 2.5. While unreinforced joints showed a 73.4% reduction in bending strength compared to solid specimens, the addition of an 8 mm carbon rod increased performance by 238.7%, restoring over 90% of the monolithic material’s strength. Numerical results confirmed that the reinforcement assumed the primary load-bearing role, effectively mitigating stresses in the polymer matrix below the ultimate tensile strength. Failure analysis clarified that the observed audible failure originated from internal fiber breakage within the rod at stresses between 900–1050 MPa. This work demonstrates that a segmental, reinforcement-based joining method can effectively overcome size constraints in polymer additive manufacturing, providing a robust and repeatable solution for rotating components subject to complex loading conditions. Full article

Background: Patent ductus arteriosus (PDA) is a common congenital heart defect. While closure of hemodynamically significant PDAs is well established, closure of small, hemodynamically insignificant PDAs for prevention of infective endocarditis or endarteritis (IEE) remains controversial and is supported only by low-level evidence. Methods: A systematic PubMed search was performed in May 2025 to identify published case reports of PDA-associated IEE. Data on PDA characteristics, audibility, vegetation location, and causative pathogens were extracted. In addition, the annual national number of percutaneous PDA closures in The Netherlands was determined using data from the Dutch Society of Pediatrics. Finally, the literature was searched for the incidence of complications of percutaneous ductal closure. Results: Seventy-two PDA-IEE cases were identified, of which fifty-five reported PDA audibility. Most cases involved audible PDAs with high-velocity turbulent flow and vegetations at sites exposed to shear stress, particularly the main pulmonary artery. Silent PDAs demonstrated similar vegetation locations and flow characteristics, suggesting that they had comparable pathophysiology. National data showed an average of 76.6 percutaneous PDA closures annually, of which 61% were hemodynamically insignificant. Adverse events during percutaneous ductal closure occur in 23.3% of procedures and clinically significant complications are reported in 10.1%. Both audible and silent PDAs appear capable of promoting IEE through similar hemodynamic mechanisms. Conclusions: Given the low incidence of PDA IEE relative to procedural risks, the high number needed to treat and the associated costs, routine closure of non-hemodynamically significant PDAs solely for IEE prevention is not clearly justified, and no distinction should be made between audible and silent PDAs. The current guidelines warrant critical reassessment. Full article

This article explores Katherine Sonderegger’s thesis that in Christian prayer, not only does the person pray, but God prays. Though such an idea runs contrary to the settled conviction in Christian spirituality that the human person prays to God, this paper enquires into the idea that God also prays in the person with a study of Ignatius of Loyola’s Spiritual Diary. That record of his spiritual experiences suggests that not only did he listen to God’s prayer in him, but that this listening comprised a spiritual itinerary in which he was led into a deeper experience of God’s prayerful laboring in him. Following this itinerary, this article proceeds in three parts. First, a study of Ignatius’s prayer to the mediators reveals that in his petitions, he sought to hear the intercessory prayer of Mary and Jesus. Second, he found himself discovering a new way to name God as he celebrated the mass; that newness resided not in a new vocabulary but in his participation in the prayer of the Son to the Father. Finally, Ignatius experienced the grace of loqüela in which he heard a kind of celestial music whose tone and language moved him to a simple, contemplative admiration of God. More than the story of a mystic with an uncommon ability to listen to God, Ignatius’s journey into greater attention to God’s language within him is the story of grace, God’s life, which is always present, active, and audible in the believer’s prayer. Full article

Conventionally designed piezoelectric micro-electro-mechanical systems (MEMS) speakers with thin-film-type, piston-type, and cantilever-type vibration membranes still adopt a Si supporting layer, which not only hinders the improvement of sound pressure level (SPL) but also lacks characterization of reliability. In this paper, we propose a fixed-end beam–cantilever piezoelectric MEMS speaker with a flexible supporting layer, achieving an SPL comparable to that of traditional three types of piezoelectric MEMS speakers with a Si supporting layer, and displaying good reliability. The measured results performed on encapsulated prototypes mounted to an acoustic test adaptor demonstrate that under a driving voltage of 1 V_rms, the SPL exceeds 51.6 dB in the human audible frequency range of 20 Hz–20 kHz, the total harmonic distortion (THD) remains below 3.4% above 430 Hz, satisfying the basic requirements for human auditory perception. Moreover, further experiments also prove its reliability by revealing no abnormal sound output, no fracture after being dropped from heights of 1 to 5 m, and the retention of over 92% SPL following 100 h of continuous music playback. This fixed-end beam–cantilever piezoelectric MEMS speakers with a flexible supporting layer provide researchers and enterprises with brand-new design ideas and a fresh perspective, which may potentially promote their development and practical application. Full article

To address the low-speed starting noise in a small electric vehicle, this study proposes and validates a systematic diagnostic and optimization methodology. A novel objective testing method, based on energy tracking and matching, is first employed for precise noise source localization. Combined with electromagnetic force wave analysis, this method identifies the coupling between a 24th-order motor excitation and a powertrain structural mode as the root cause. Subsequently, a low-cost, integrated optimization scheme is presented, which synergistically combines three strategies: motor control refinement, powertrain natural frequency tuning, and mount isolation enhancement. Experimental validation demonstrates that this multi-domain approach reduces the sound pressure level at the driver’s ear by 4–6 dB(A), effectively eliminating the abnormal audible noise during starting and significantly improving the in-cabin sound quality. This paper offers a cost-effective engineering framework for resolving low-speed, low-frequency noise problems in electric vehicles. Full article

The growing miniaturization of electronic systems and the expansion of sustainable, autonomous IoT technologies emphasize the need for efficient, ultra-low-power energy harvesting devices. This study evaluates fifteen devices from five industry leaders for use in small-scale autonomous seed germination systems. Its novelty lies in applying a competitive profile matrix within a flexible multicriteria evaluation framework based on the simple additive weighting (SAW) method that uses a comprehensive set of competitive technology factors (CTFs). The results demonstrate that a transparent and structured methodology can generate prioritized lists of suitable energy harvesters while accounting for technical, economic, and environmental trade-offs. The study also shows that device rankings depend on the scope and objectives of the project. If these change, then the CTF selection, classification, and weighting adjust accordingly. Therefore, the relevance of this study lies in the adaptability, replicability, and audibility of the proposed framework, which supports the selection of informed technology for autonomous, IoT-based germination systems and other technological projects. Full article

Acoustically, Baroque theatres have prove remarkably appropriate for opera, and, in the past, little distinction was drawn in design between drama and opera use, except for the inclusion of an orchestra pit, because both music and words were audible and balanced, reverberation times being shorter than in concert halls but longer than in speech auditoria. In a drama configuration, scenery is set in the fly tower on stage, while for opera pieces, in most cases, the orchestra pit platform raises to the main floor level of the stalls to set additional seats rows. Considering the characteristics of the Opera di Roma (IT), the case study, the main physical parameters that contribute to the sound quality are evaluated and compared in relation to the pit position level, in order to understand the possible merits of the covering seats on the pit surface for drama representations and, more generally, for speech activities. Eight different configurations are compared and, to evaluate the acoustic parameters’ sensitivity, the JND (just noticeable difference) is analyzed. The parameters’ trend is described. Full article

This study aimed to investigate the effect of inaudible-frequency binaural beats (BB), excluding the influence of audible sound, on visuospatial working memory performance (VSWMP). In particular, the effects were examined in relation to the stimulation timing of the stimulus and the task performance level of participants. Thirty adults in their 20 s (20 males, 25.7 ± 1.8 years; 10 females, 24.3 ± 1.6 years) participated in the experiment. A 10 Hz BB stimulus was generated by simultaneously presenting 18,000 Hz and 18,010 Hz tones to the left and right ears, respectively. The experiment employed a within-participant design consisting of a rest phase (5 min) and a task phase (5 min), with four BB stimulation conditions: Control (no BB), Exp1 (BB during both rest and task phases), Exp2 (BB during rest only), and Exp3 (BB during task only). VSWMP was assessed using corrected hit rate and reaction time in a 3-back task. Results indicated that all BB conditions (Exp1, Exp2, Exp3) significantly improved VSWMP compared to the Control condition, regardless of the stimulation timing. When participants were grouped based on task performance level into high- and low-performing groups (HPG, LPG), significant improvements in VSWMP were particularly evident in the LPG across all BB conditions compared to the Control. Notably, in Exp3, LPG participants demonstrated VSWMP comparable to that of the HPG. In conclusion, while BB stimulation enhances VSWMP regardless of its stimulation timing, its effectiveness may vary depending on the task performance level. Full article

Timely tool wear detection has been an important target for the metal cutting industry for decades because of its significance for part quality and production cost control. With the shift toward intelligent and sustainable manufacturing, reliable tool-condition monitoring has become even more critical. One of the main challenges in sound-based tool wear monitoring is the presence of noise interference, instability and the highly volatile nature of machining acoustics, which complicates the extraction of meaningful features. In this study, a Convolutional Neural Network (CNN) model is proposed to classify tool wear conditions in milling operations using acoustic signals. Sound recordings were collected from tools at different wear stages under two cutting speeds, and Mel-Frequency Cepstral Coefficients (MFCCs) were extracted to obtain a compact representation of the short-term power spectrum. These MFCC matrices enabled the CNN to learn discriminative spectral patterns associated with wear. To evaluate model stability and reduce the effects of algorithmic randomness, training was repeated three times for each cutting speed. For the 520 rpm dataset, the model achieved an average validation accuracy of 96.85 ± 2.07%, while for the 635 rpm dataset it achieved 93.69 ± 2.07%. The results demonstrate the feasibility of using acoustic signals, despite inherent noise challenges, as a complementary approach for identifying suitable tool replacement intervals in milling. Full article

Quiet drivetrains have become a central requirement in modern electric vehicles, where the absence of engine masking makes even subtle gear tones clearly audible. As a result, manufacturers are looking for more reliable ways to understand how design choices, manufacturing variability, and operating conditions shape gear noise and vibration. Digital Twin (DT) approaches—linking high-fidelity models with measured data throughout the product lifecycle—offer a potential route to achieve this, but their use in gear NVH is still emerging. This review examines recent work from the past decade on DT concepts applied to gears and drivetrain NVH, drawing together advances in simulation, metrology, sensing, and data exchange standards. The survey shows that several building blocks of an NVH-oriented twin already exist, yet they are rarely combined into an end-to-end workflow. Clear gaps remain. Current models still struggle with high-frequency behavior. Real-time operation is also limited. Manufacturing and test data are often disconnected from simulations. Validation practices lack consistent NVH metrics. Hybrid and surrogate modeling methods are used only to a limited extent. The sustainability benefits of reducing prototypes are rarely quantified. These gaps define the research directions needed to make DTs a practical tool for future gear NVH development. A research Gap Map is presented, categorizing these gaps and their impact. For each gap, we propose actionable future directions—from multiscale “hybrid twins” that merge test data with simulations, to benchmark datasets and standards for DT NVH validation. Closing these gaps will enable more reliable gear DTs that reduce development costs, improve acoustic quality, and support sustainable, data-driven NVH optimization. Full article

This study investigates the vibration and noise characteristics of oil-immersed power transformers, with a particular focus on the influence of transformer oil on structural dynamics and acoustic emission. The research integrates multi-physics modelling, finite-element simulation, and field measurements to analyze the vibration transmission paths from the core and windings to the tank wall. A fluid–structure interaction (FSI) model is developed to account for the damping effect of insulating oil, and a correction factor is introduced to adjust modal parameters. Simulation results reveal that oil significantly enhances vibration propagation, especially in the vertical direction, while structural ribs and clamping configurations affect local vibration intensity. Noise simulations show that magnetostriction is the dominant source of audible sound, with harmonic components sensitive to load and voltage variations. Experimental validation using a portable sound level meter confirms the simulation trends and highlights the spatial variability of acoustic pressure. The findings provide a theoretical and practical basis for optimizing sensor placement and developing voiceprint-based diagnostic tools for transformer condition monitoring. Full article

We present a photoacoustic spectroscopy (PAS)-based method using a laser Doppler vibrometer (LDV) for real-time detection of laser-induced damage (LID) in optical components. By measuring audible frequency surface vibrations, the method enables remote, non-contact, and sensitive detection. Experiments with various dielectric optics (slide glass and single-layer coatings) and pulse durations (7 ns and 360 ps) of an Nd:YAG laser (wavelength of 1064 nm) showed detection accuracy comparable to microscopy. Vibration spectra correlated with natural modes calculated by finite element modeling, and vibrations according to the detecting location were observed. The method remained effective under typical mounting conditions, demonstrating its practical applicability. This PAS-LDV approach offers a promising tool for in situ monitoring of LID in high-power laser systems. Full article

This paper proposes a metal defect detection method based on laser-induced audible sound testing (LAST). Defective and defect-free martensitic stainless-steel cubes were used as study samples, and the spectral characteristics of the acoustic signals generated under laser irradiation were comparatively analyzed. Based on F-ratio analysis, weighting curves characterizing the discrimination capability of each frequency band were calculated. Subsequently, nonlinear filter banks were designed according to the spectrum discrimination weights, tailored to the degree of spectrum discrimination. Finally, a globally weighted cepstral coefficient (GWCC) extraction algorithm for laser-induced acoustic signals was developed to determine whether defects are present in metals. Experimental results show that the recognition rate of defective samples based on GWCC features reached 94%, higher than that of traditional acoustic features, effectively enhancing feature discriminability. The results of this study demonstrate that applying LAST to metal defect detection is feasible. This method leverages laser-generated acoustic signals from a more comprehensive and economical perspective, pioneering a new solution for non-destructive testing of metal defects. Full article

Background: First rib stress fractures (FRSFs) are exceptionally rare in skeletally immature athletes and are frequently overlooked because their symptoms mimic more common scapular conditions such as scapular dyskinesis or thoracic outlet syndrome. Early and accurate identification is critical to avoid delayed union, prolonged disability, and misdirected management. Case Presentation: We report a 12-year-old elite baseball pitcher with progressive scapular winging and audible snapping during pitching. Unlike typical posterior-type fractures near the costotransverse joint, imaging revealed a cortical discontinuity precisely at the serratus anterior enthesis, consistent with repetitive traction enthesopathy. High-resolution musculoskeletal ultrasound (MSK-US) identified cortical disruption with periosteal edema, and dynamic ultrasound reproduced the patient’s snapping and pain in real time, establishing a direct clinical–imaging correlation. Conservative three-phase rehabilitation (scapular stabilization, serratus anterior activation, and structured return-to-throwing) led to complete union and pain-free return to sport within 12 weeks. Discussion: This case highlights the superior diagnostic efficacy of MSK-US for FRSFs in adolescents. The posterior scanning approach facilitated bilateral comparison and growth plate assessment. Dynamic examination provided a functional correlation beyond static imaging, identifying a novel snapping mechanism. This underscores the value of MSK-US in visualizing not just anatomy but also pathophysiology. Conclusions: This is among the youngest documented cases of first rib stress fracture diagnosed with dynamic ultrasound. Its novelty lies in the following: (1) occurrence at the serratus anterior enthesis, (2) reproduction of snapping during provocative maneuvers, and (3) expansion of the etiological spectrum of scapular dyskinesis to include rib pathology. Dynamic ultrasound should be considered a frontline modality for adolescent throwers with unexplained periscapular pain. Full article

Responsiveness—the speed at which a text-to-speech (TTS) system produces audible output—is critical for real-time voice assistants yet has received far less attention than perceptual quality metrics. Existing evaluations often touch on latency but do not establish reproducible, open-source standards that capture responsiveness as a first-class dimension. This work introduces a baseline benchmark designed to fill that gap. Our framework unifies latency distribution, tail latency, and intelligibility within a transparent and dataset-diverse pipeline, enabling a fair and replicable comparison across 13 widely used open-source TTS models. By grounding evaluation in structured input sets ranging from single words to sentence-length utterances and adopting a methodology inspired by standardized inference benchmarks, we capture both typical and worst-case user experiences. Unlike prior studies that emphasize closed or proprietary systems, our focus is on establishing open, reproducible baselines rather than ranking against commercial references. The results reveal substantial variability across architectures, with some models delivering near-instant responses while others fail to meet interactive thresholds. By centering evaluation on responsiveness and reproducibility, this study provides an infrastructural foundation for benchmarking TTS systems and lays the groundwork for more comprehensive assessments that integrate both fidelity and speed. Full article