Absorbance Characteristics Research Articles

Investigation of ambient-pressure absorbance characteristics of cartilage-grafted tympanic membranes.

To investigate alterations in middle-ear mechanics after type 1 cartilage tympanoplasty by comparing the ambient pressure absorbance values of the perforated tympanic membrane, normal tympanic membrane and cartilage-grafted tympanic membrane. Twenty patients diagnosed with non-suppurative chronic otitis media and 20 healthy controls were included. Pure tone audiometry and wideband tympanometry were performed once in the healthy controls and pre-operatively, one month and three months post-operatively in the patients. Using wideband tympanometry, the patients' three-month post-operative ambient pressure absorbance values were found to be similar to those of the healthy controls at low frequencies, while lower ambient pressure absorbance values were recorded at middle and high frequencies. Air-bone gap and ambient pressure absorbance values showed significant negative correlations at 1000 and 4000 Hz both pre- and post-operatively. Generally, the patients' ambient pressure absorbance values were significantly lower at middle and high frequencies than those of the healthy controls. Post-operative wideband tympanometry is a practical tool for investigating the effects of a repaired tympanic membrane on middle-ear dynamics.

Analysis and research on the dynamic characteristics of shock absorber based on ADAMS

In order to effectively improve safety and stability during transportation, a shock absorber with buffering and self-locking functions was designed. Based on the rigid flexible coupling technology, the working state and dynamic response of the shock absorber were simulated and analyzed. The linear spring was treated as a flexible body, and the cam button, guide pillar, and base were treated as rigid bodies. The modal neutral files required for the rigid flexible coupling dynamic analysis were generated. Based on ADAMS, a dynamic simulation model was established, replacing a part of the rigid model with a flexible model and conducting load response analysis on it. To further improve the vibration reduction effect, the performance of the contact material of the shock absorber was analyzed. Through the calculation of dynamic characteristics, it could be known that the self-locking mechanism had no dead points, and the vibration reduction force response stability was high, meeting the working requirements.

Exploring 4-chloro chalcone: Synthesis, spectroscopic, chemical reactivity, topological, hirshfeld surface, drug-Likeness, molecular docking and assessment of electronic properties in diverse solvents

Chalcones are a significant class of naturally occurring chemical substances and their derivatives are extremely influential in the field of biological industries. In the current study, the title composite,4 - Chlorochalcone has undergone extensive investigation to understand its spectral properties using a combination of experimental and theoretical calculations. Fourier transform (FT-IR) infrared and FT-Raman characterizations provided valuable insights into the vibrational assignments (functional groups) in the header molecule, while ultraviolet–visible (UV–Vis) spectroscopy explored its electronic transitions and absorbance characteristics. The electronic properties were studied for the solvents viz., ethanol, methanol, DMSO, acetonitrile and benzene through theoretical-computational DFT calculations, revealing details about their molecular orbitals, electronic energies, and other energy parameters. Additionally, the NBO-natural bond orbital analysis shed light on the chemical bonding and electron distributions by donor and acceptor atoms. Furthermore, MEP- molecular electrostatic potential was analyzed for the various solvents and the calculated energy parameters were obtained. A drug-likeness evaluation was performed to assess its potential as a drug candidate based on its molecular properties. Moreover, the topological analysis and electron-hole distributions, contributed to a comprehensive understanding of electron density and localization within the molecule for the solvents viz., ethanol, methanol, DMSO, acetonitrile and benzene. Molecular docking investigations, as well as the Ramchandran plots, revealed that substituents targeting amino acids contribute to the antiviral action of the header compound. The potential of 4′-Chlorochalcone (ligand) as an antiviral agent offers promising prospects for further exploration and development in various therapeutic areas within the field of medicinal chemistry.

Studying the Improvement of Solar Collector Mechanism with Phase Change Materials

This study delves into the integration of phase change materials (PCM) in solar thermal collector systems to address this challenge. By incorporating nano encapsulated PCMs, researchers have mitigated concerns surrounding PCM leakage, revolutionizing the potential of solar collector systems to elevate energy efficiency, diminish carbon emissions, and yield manifold benefits. This article comprehensively investigates the design and utilization of solar phase change energy storage devices and examines the transformative impact of employing nano-coated phase change materials (Nano capsules) to augment solar collector performance. The integration of paraffin-based PCM and the insulation of the collector system have been crucial in optimizing heat retention and operational efficacy. The composition of the PCM involves a balanced blend of octadecane phase-change particles and water as the base fluid, designed to maximize thermal performance. Analysis of the experimental findings demonstrates the dynamic thermal behavior of the nano encapsulated phase change material, revealing distinctive temperature profiles about fluid dynamics and absorbent characteristics. Notably, the study emphasizes the nuanced trade-offs associated with the conductivity and melting temperature of the Nano encapsulated PCM, yielding valuable insights into energy storage capacity limitations and thermal performance variations throughout diurnal cycles. Central to the investigation, the optimal nanoparticle proportion is elucidated, shedding light on its pivotal role in modulating PCM performance. Furthermore, findings underscore the complex interplay between nanoparticle volume fraction and thermal fluid temperature, providing critical perspectives on optimizing PCM-enhanced solar collector systems.

Electron‐Deficient Boron‐Doped g‐C3N4 as an Efficient and Robust Photocatalyst for Visible‐Light Driven Hydrogen Evolution from Water Splitting

AbstractElemental doping is considered to be a promising approach for altering the electronic structure, optical absorbance, and charge separation characteristics of graphitic carbon nitride (g‐C3N4, termed as CN), thus boosting its photocatalytic performance for practical applications. Herein, a series of boron (B) doped g‐C3N4 (named as BCN) photocatalysts are developed via one‐step pyrolysis of a mixture of urea and 3‐methoxycarbonyl‐5‐nitriophenylboronic acid (MCNPBA). The results show that B‐atoms have been successfully incorporated into the g‐C3N4 network. The as‐synthesized BCN‐x (x shows the weight content of MCNPBA) photocatalysts are evaluated in photocatalytic hydrogen (H2) evolution from water splitting under visible‐light (λ ≥ 420 nm). The optimized BCN‐10 sample shows a maximum H2 evolution rate of 1789.93 µmol h─1 g─1, which is 6.2 times higher than that of g‐C3N4 (289.73 µmol h─1 g─1). This is attributed to the fact that the electron‐deficient B‐atoms are lewis acids that trap electrons, which in turn expands visible‐light absorption, narrows the bandgap, and prevents the recombination of photogenerated charge carriers. Moreover, B‐doping can readily modify the valence and conduction band positions of g‐C3N4, therefore augmenting the photocatalytic H2 evolution activity. This paper presents a unique rational framework for developing other functionalized electron‐deficient elemental‐doping g‐C3N4‐based photocatalysts for practical applications in solar‐to‐fuel conversion.

Adjustable graphene disk‐based THz absorber for biomedical sensing: Theoretical description

AbstractAs a basic building block, the THz wave absorber has intense imaging, sensing, and nondestructive testing applications. There are several methods for tuning THz absorbers, including electricity modulation, light modulation, mechanical tuning, using phase change materials, liquid crystal, flexible materials, MEMS technology, and thermally tuning vanadium dioxide. The choice of tuning method depends on the specific application and the desired performance characteristics of the THz absorber. In this work, we report a theoretical description of mechanically tunable THz absorber based on overlapping periodic arrays of graphene nano‐disks. The basis of this work is based on the movement of a dielectric surface covered on both sides with graphene disks. This surface moves on a fixed plane while the distance between these two surfaces is free space. Also, the fixed surface consists of a relatively thick layer of gold at the bottom, dielectric on it, and graphene disk patterns on the dielectric. Now, by moving the movable surface in the horizontal direction, it is possible to adjust the amount of absorption in different frequencies of the terahertz (THz) band. Additionally, an equivalent RLC circuit model is developed and theoretical results match with simulated data. The proposed mechanically tunable THz absorber can be exploited in various emerging applications such as sensing due to its capability of covering all of the THz gap and beyond with multiple absorption peaks.

The sound absorption properties of a double-leaf micro perforated panel (DL-MPP) made from a double-layered polypropylene material.

Micro-perforated panel sound absorbers are recognized as an alternative method for noise control, offering advantages over conventional porous absorbers. However, the sound absorption of a single micro-perforated panel (MPP) is limited in its ability to cover a broad range of frequencies, especially in the low-frequency region. Therefore, the primary focus of this study is to investigate the sound absorption performance of a double-leaf micro-perforated panel (DL-MPP) absorber, which aims to achieve high sound absorption across a wide frequency range. This study examines the impact of varying parameters, including perforation ratio, diameter of perforated holes, and air gap thickness, on the sound absorption characteristics of a polypropylene-based DL-MPP absorber. Polypropylene was used as the sound absorption material for this investigation. The DL-MPP absorber consists of two perforated panels installed parallel to a rigid back wall, with an air gap between them. To assess the sound absorption performance, a prototype of the DL-MPP absorber was fabricated and tested using a two-microphone impedance tube method following ASTM E1050 standard. The results demonstrate that the optimal sound absorption performance was achieved by designing the MPPs with a 1% perforation ratio, 1 mm diameter of perforated holes, and a 1 mm sample thickness.

Velocity and load dependent dynamic shock absorber friction at stationary conditions

When it comes to vehicle vertical dynamics, the characteristics of shock absorbers are of high importance. With the increasing use of active suspension systems, it becomes possible to adapt the hydraulic damping force to the road event, while the friction force is not controllable. As a result, friction becomes more relevant and can negatively affect passenger ride comfort. In many mechanical applications, it is observed that friction in lubricated sliding conditions is velocity and load dependent. In contrast, shock absorber friction, and therefore suspension friction, is commonly considered as quasi-static, i.e. characterised by a constant potential. Since the shock absorber is predominantly in motion over a wide velocity range, it is necessary to improve the understanding of friction characteristics especially in the dynamic domain. In this study, modified valve-free shock absorbers are presented that allow the observation of dynamic friction properties experimentally. As not covered by previous studies, the effect of side force (load) as a main parameter to increase friction is investigated. It is observed that its effect varies significantly with velocity and alters the stationary friction-velocity curve, also known as the Stribeck curve. In addition, the shape of the Stribeck curve depends strongly on the shock absorber's oil volume. These novel results emphasise a substantial, interdependent influence of load and velocity on the (elasto-)hydrodynamic properties of the dynamic shock absorber friction force, which was not identified in the literature. The dynamic friction force exceeds the quasi-static friction force multiple times, and also exceeds the hydraulic damping force for considerable side forces in the lower velocity range up to 60 mm/s. Consequently, the total shock absorber force under presence of side force is determined. The findings can be used to improve active suspension control or to improve vehicle simulation by enabling the parametrisation of dynamic shock absorber friction models.

Electromagnetic shielding, absorption and physicochemical evaluations of Fe3N @ C nanocomposite decorated with Poly(DCBP-co-BT) for absorption application in 8-12 GHz

Multipurpose electromagnetic shielding materials with high absorption and low reflection are a potential topic for upcoming advancement in the fabrication industry. Nevertheless, the task of effectively incorporating these traits into the same material remains challenging. In the current work, Fe3N @ C nanocomposite wrapped in Poly(4,4′-di(N-carbazoyl)bipheny-co-2,2′-bithiophene) polymer is fabricated for absorbance-based shielding material which exhibits significant absorbance and minimal reflection characteristics. The microwave absorption features of as-synthesized material were studied for different loading ratios and it has achieved minimum reflection loss (RLmini) of − 39 dB having 2.0 mm thickness for 8 wt% loading sample. Shielding effectiveness of the fabricated nanocomposite was also measured, and the sample with 8 wt% filler loading had a high electromagnetic interference shielding efficacy of − 60 dB at 8.5 GHz. Additionally, high absorption capacity (−30 dB) and excellent shielding effectiveness (−60 dB) make this nanocomposite a special one that may be used as a radar-absorbing coating to shield against electromagnetic radiation interference. Thus, such adaptive shielding material possesses essential uses in electromagnetic shielding due to its exceptional capacity for absorption and remarkable efficiency in shielding.

Manipulating the phase and morphology of MgFe2O4 nanoparticles for promoting their optical, magnetic, and microwave absorbing/shielding characteristics

Morphology and phase regulation shed light on the tuning of microwave absorbing characteristics, as well as magnetic and optical features. Not only is the development of electromagnetic wave absorbing materials the best way to equip us against harmful electromagnetic waves in the technology era, but the widespread applications of microwave absorbers in military and civilian fields have also enhanced their importance. Hence, MgFe2O4 nanoparticles were synthesized, and then (1) its main crystalline phase was divided into Mg, Fe2O3, and Fe3O4, and (2) its morphology was manipulated to evaluate the influence of morphology and phase on the microwave absorbing performance, optical characteristics, and magnetic capability. The novel precursors, along with modified sol-gel and solvothermal scenarios, were applied to regulate the structures toward strengthening the features. Interestingly, polyethylene terephthalate (PET) was chosen as the recyclable plastic to fabricate the final composites to evaluate the microwave absorbing/shielding characteristics due to its fascinating susceptibilities as building materials, minimizing environmental hazards and implementing green and sustainable manufacturing. Noticeably, Mg/Fe3O4/PET nanocomposite gained a brilliant RL of −95.50 dB at 21.80 GHz meanwhile the one-pot-synthesized Fe2O3/MgFe2O4 composited by PET attained a maximum RL of −71.32 dB at 23.06 GHz and an ultra-high efficient bandwidth (RL ≤ −20 dB) of 8.50 GHz with only thickness of 0.50 mm. Interestingly, the PET-based microwave absorbers were fabricated with a low filling ratio of 10 wt%. More significantly, the samples illustrated proper shielding efficiency, desirable for practical applications in the modern era.

Flexural behaviour of cementitious composites embedded with 3D printed re-entrant chiral auxetic meshes

3D printed auxetic metamaterials can be used to make high performing cementitious composites to strengthen existing structures and elements due to their negative Poisson’s ratio behaviour and high energy absorbing characteristics. In this paper, three different re-entrant chiral auxetic (RCA) meshes of various cell geometries and orientations were developed by 3D printing them using poly-lactic acid (PLA) and thermoplastic polyurethane (TPU) filament. The developed meshes were tested under out-of-plane flexure to study their load carrying capacity, ductility and energy absorption characteristics, especially to characterise the best cell orientation. The horizontal cells provided enhanced load carrying and energy absorption characteristics for all three cell geometries for both materials. These RCA meshes were then embedded into low and high strength premix cement mortar matrices to develop auxetic cementitious composites (ACCs). In total, 42 ACC specimens were casted and tested under flexural loading. The results were studied in terms of their failure patterns, load-displacement responses, flexural capacities, ductility and energy absorption. The RCA meshes made of PLA filament showed limited capacity and energy absorption as compared to RCA meshes made of TPU filament due to extended flexibility and resilience provided by TPU meshes. The RCA meshes with a denser cell structure exhibited highest flexural capacity and effective energy absorption of 14 700 kJ m−2 for TPU-RCA mesh embedded into high strength cement mortar matrix. The results obtained in this study have enabled to understand the flexural behaviour of cementitious composites embedded with 3D printed auxetic lattices and to strengthen the existing structures.

Performance of new designed meta-material absorbers/emitters reshaping solar spectrum to double-narrowband emissive spectrum for STPV power generation

Solar thermophotovoltaic system can reshape the solar spectrum and improve the conversion efficiency of photovoltaic. In this study, the characteristics of ideal selective absorber for AM0 and AM1.5 solar spectra are compared, and the principles are summarized to design a metamaterial absorber for different spectra. The absorption efficiency can reach more than 80 % at the high temperature of 1700 K. This study innovatively proposes a STPV system that matching a double-narrowband (DNB) emitter with Si/InGaAsSb tandem cells. The theoretical efficiency of STPV with a DNB emitter is about 4 % higher than that with a wide-band (WB) emitter by analyzing thermodynamic model. Accordingly, a metamaterial DNB emitter is designed. The results show that the DNB metamaterial selective emitter designed in this study can achieve a TPV efficiency of near 50 %. The concentrating ratio and temperature have an inverse effect on the absorption efficiency and TPV efficiency. The optimized STPV system efficiencies for AM0 and AM1.5 are 37.29 % and 37.20 % under typical condition, respectively, which are a great improvement compared to the solar PV cell. The proposed metamaterial absorber and DNB emitter have great application potential in power generation for both space and ground conditions.

The effect investigates of temperature on the optical and electrical properties of sprayed SnS: experimental and theoretical study

In this study, Tin monosulfide SnS semiconductor absorbers was deposited by chemical spray pyrolysis route on the glass substrate. We examined the impact of substrate temperature on the structural, morphological, linear optical and electrical characteristics of SnS absorber at many substrate temperatures such as 50 °C, 375 °C and 400 °C. The SnS films have been analysed by diverse techniques like X-ray diffraction, Raman spectroscopy, Scanning electron microscopy and UV-Vis spectrophotometer. The X-ray diffraction (XRD) spectra revealed that the SnS crystallize in the orthorhombic crystal system with the apparition of the preferential crystallographic direction oriented along (111) planes. The SEM micrographs indicate a great uniformity and granular morphological surface of SnS films. Linear optical constants such as energy gap (Eg), coefficient of extinction (k), index of refraction (n), optical conductivity (σopt), as well as the electrical properties confirm the suitable application of SnS thin films as absorber layer in the optoelectronic device applications. Additionally, we have applied the density functional theory DFT and GGA generalized gradient approximation to study the electronic characteristics; as a result of the electronic band structure the SnS absorber has a suitable energy gap.

An in-depth investigation of lead-free KGeCl3 perovskite solar cells employing optoelectronic, thermomechanical, and photovoltaic properties: DFT and SCAPS-1D frameworks.

Potassium germanium chloride (KGeCl3) has emerged as a promising contender for use as an absorber material for lead-free perovskite solar cells (PSCs), offering significant potential in this domain. In this study, we conducted a density functional theory (DFT) investigation to analyze and assess the structural, electronic, thermomechanical, and optical characteristics of the cubic KGeCl3 absorber. The positive phonon dispersion curve confirmed the dynamical stability of KGeCl3. The elastic constant satisfied the Born criteria, validating the mechanical stability and ductility of solid KGeCl3. The electronic band structure and density of states (DOS) confirmed that the KGeCl3 material is a semiconductor with a direct band gap of 0.754 eV (GGA) and 0.803 eV (mGGA-RSCAN). The study identified key optical parameters, including absorption, conductivity, reflectivity, dielectric function, refractive index, and loss function, revealing the potential suitability of KGeCl3 for solar applications. The Helmholtz free energy (F), internal energy (E), entropy (S), and specific heat capacity (Cv) are computed based on the phonon density of states. Additionally, we investigated twenty-four configurations comprising different combinations of electron transport layers (ETLs) and hole transport layers (HTLs) in SCAPS-1D software. For this purpose, ETLs such as Ws2, ZnSe, PCBM, and C60 and HTLs such as CBTS, CdTe, CFTS, Cu2O, P3HT, and PEDOT:PSS are employed. The highlighted structure, ITO/CBTS/KGeCl3/Ws2/Ni, demonstrates remarkable performance with an efficiency of 22.01%, a Voc of 0.6799 V, a Jsc of 41.439 mA cm-2, and a FF of 78.12%. To analyze photovoltaic (PV) performance, we chose the top four solar cell (SC) configurations. Moreover, a comprehensive examination was conducted to assess the impact of various factors, including the thickness of different layers, capacitance, Mott-Schottky behavior, series and shunt resistance, temperature, and generation-recombination rates, as well as J-V (current-voltage density) and quantum efficiency (QE) characteristics.

Enhanced Efficiency of Tandem Perovskite Solar Cells Utilizing Cs2BiAgI6 and La2NiMnO6 Double Perovskite Absorbers with Optimized Charge Transport Layers

This study investigates the application of Cs2BiAgI6 and La2NiMnO6 double perovskite compounds as absorbers in perovskite solar cells (PSCs). Computational simulations were employed to assess the performance of these compounds in isolation, employing various hole transport layers (HTLs). The simulations were geared towards optimizing the HTL thickness for each absorber, ensuring proficient charge transport and current alignment. Through these simulations, valuable insights into the electronic properties and light absorption characteristics of the individual absorbers were obtained. Subsequently, a tandem simulation was executed, aligning the current outputs of both devices through precise adjustment of thickness. This tandem configuration was designed to maximize the overall efficiency of the PSC system. The simulation outcomes explicitly demonstrated that the integration of Cs2BiAgI6 and La2NiMnO6 in a tandem configuration led to superior performance in comparison to the standalone absorbers. The optimized HTL thicknesses facilitated enhanced charge transport and guaranteed current alignment between the two devices. This paper offers significant contributions to the conceptualization and fine‐tuning of tandem PSCs utilizing Cs2BiAgI6 and La2NiMnO6 as absorber materials, presenting potential avenues for augmenting the overall efficiency of PSC systems. Subsequently, further optimization of the tandem configuration led to an impressive power conversion efficiency (PCE) of 30.256%, open circuit voltage (Voc) of 1.682 V, fill factor (FF) of 79.74%, and short‐circuit current density (Jsc) of 24.11 mA/cm2, respectively.

Effect of absorber characteristics on O-type traveling wave tube operation

Effect of absorber characteristics on O-type traveling wave tube operation

Assessment of the Possibility of Validating the Durability Testing Method for Large-Sized Vehicles Based on Changes in Shock Absorber Characteristics—Preliminary Tests

The use of road simulators in vehicle durability tests enables a significant reduction in time related to the implementation of a new product. However, there is still a need to improve the methods of these tests in order to obtain a full correlation between the time of the tests on the simulator with respect to the mileage of the vehicle in real road conditions. The aim of this work is a validation and improvement of the durability testing method for large-sized vehicles. Comparative tests of shock absorbers dismantled from semi-trailers with different mileage and shock absorbers dismantled from semi-trailers after durability tests conducted at the MTS test bench are presented. The relationship between the maximum damping force and the displacement speed of the shock absorber piston was examined. Additionally, the influence of the shock absorber temperature on the damping force was analyzed. As a result of the tests, the dynamic characteristics of the shock absorbers were determined and the relationship between the maximum damping force and the mileage of the trailers was determined. It was found that the load on the trailers during their operation has a significant impact on the change in the characteristics of the shock absorbers. What is new in this publication is the validation of the methodology for conducting durability tests previously proposed by the authors based on the selected component, which is the shock absorber. The authors have not yet encountered in the literature any attempt to validate the methodology for conducting durability tests for large-sized vehicles.

Experimental and Numerical Study of Shock Absorber Characterization and The Implication on The Dynamics of Half Vehicle Suspension System Model

This study aimed to characterized shock absorber damping for passenger comfort. The riding comfort of the vehicle has direct correlation to the damping characteristic of the shock absorber of the suspension system. Two different shock absorbers were experimentally evaluated, and their damping characteristics were integrated into a half-car model to study the vehicle's dynamic response to harmonic road disturbances. The investigation involved numerical simulations of the half-car model subjected to harmonic road disturbances, represented by a set of ordinary differential equations solved using the Dormand-Prince method. Experimental data yielded average damping forces of 502.77 N for shock-absorber #1 and 192.03 N for shock-absorber #2. Calculations resulted in damping coefficients of 3888.57 N·s/m for shock-absorber #1 and 1397.85 N·s/m for shock-absorber #2, with corresponding damping ratios of 0.29 and 0.105. These damping ratios generally aligned with typical values for passenger car shock absorbers, except for shock-absorber #2, which deviated from the expected range. The study found that at 60 km/h and 90 km/h, shock-absorber #1 with ζ=0.29 exhibited superior performance in reducing displacement amplitude compared to shock-absorber #2 at ζ=0.105. However, at 120 km/h, both shock-absorbers displayed similar responses, with shock-absorber #1 slightly surpassing shock-absorber #2 in displacement amplitude.

A parallel piezoelectric micro-perforated panel absorber with flexible acoustic characteristics

In this paper, the sound absorption characteristics of a parallel micro-perforated panel absorber (MPPA) fabricated from polyvinylidene fluoride (PVDF) piezoelectric film are studied under an alternating voltage excitation. The simulation and experimental results show that when a certain frequency of AC voltage is applied to the parallel micro-perforated panel, the sound absorption characteristics of the MPPA at the excitation frequency can be improved due to the electrically induced vibration. With an increase in the alternating voltage amplitude, the improvement in sound absorption characteristics is more obvious. Therefore, the sound absorption coefficient of parallel PVDF-MPPA in the target frequency band can be improved by adjusting the parameters of excitation voltage reasonably. Based on the convenience of voltage regulation, this method is very suitable for suppressing the noise of the main frequency fluctuation without changing the structural parameters of the absorber. More importantly, the parallel PVDF-MPPA can apply voltage excitations of different parameters simultaneously, which is beneficial to improve the sound absorption effect in a wider frequency band. This study may provide a reference for the design of intelligent absorbers, especially for noise reduction structures in narrow spaces.

A measurement method for the estimation of the absorption characteristics of finite-sized porous absorbers

The estimation of sound fields generated inside enclosures has gained increasing interest in the recent years, both for acoustic design purposes and virtual reality applications. Numerical simulation methods require detailed information on the impedance/absorption characteristics of the enclosing surfaces. The currently available measurement methods are only capable of obtaning the point-like impedance of locally reacting surfaces. We present a new measurement technique to characterize extended reacting absorbing surfaces. The measurement is done by scanning the surface with a PU-probe, and the asborption characteristics are obtained by a Helmholtz-integral based postprocessing step.