Low Frequency Range Research Articles

Broadband low-frequency sound insulation of stiffened sandwich PFGM doubly-curved shells with positive, negative and zero Poisson's ratio cellular cores

Compared to the conventional cellular cores, the cellular cores auxetic metamaterials with negative and zero Poisson's ratios have unique mechanical deformation characteristics, which can be further applied to modeling lightweight sandwich structures. Based on that, the sound transmission characteristics of a novel stiffened sandwich porous functionally graded materials (PFGM) doubly-curved shells with full Poisson's ratio characteristic range cellular cores are investigated in this study. The adjustment of material properties of PFGM face sheets in the thickness direction is achieved through power law based on component volume fraction, and the core layer consists of cellular cores with positive, negative, and zero Poisson's ratios (PPR, NPR, and ZPR). Two common types of stiffened sandwich shell types, namely, the shell with PFGM face sheets and metal-rich cellular cores (type-A), and the ceramic-rich cellular cores (type-B), are discussed, and the Hamilton's principle is used to derive the governing equations. By applying normal velocities continuity conditions at the fluid-structure interface to consider fluid-structure coupling, which is further analytically solved using Navier's technology, and the average sound transmission loss (STL) with broadband low-frequency is described. The effectiveness of the established theoretical model is confirmed by comparing it with previously published results, experimental and simulated results obtained by impedance tube and COMSOL commercial software. A systematic comparison is conducted on the performance of stiffened sandwich PFGM doubly-curved shells with full Poisson's ratio characteristic range cellular cores, and the results show superior performance in the sound insulation for the sandwich shell with ZPR cellular cores, considerably at a broad low-frequency range of 220–2040 Hz, in comparison with the sandwich shell with NPR cellular cores and conventional PPR cellular cores types. This work's findings can serve as a benchmark for future studies and help to design and create engineering sandwich structures with improved sound insulation properties.

Meta-structure enhanced second harmonic S0 waves for material microstructural changes monitoring

Cumulative second harmonic Lamb waves in nonlinear media feature increasing amplitudes with propagation distance, conducive to the monitoring of material microstructural changes in structures. The phenomenon can be readily generated by zero-order symmetric (S0) mode waves in the low-frequency range. However, in a practical piezoelectric-transducer-activated system, both S0 and A0 (zero-order antisymmetric) mode Lamb waves are inevitably excited, while only the former is responsible for cumulative effects. The generation efficiency of the cumulative second harmonics is then affected by the presence of the A0 waves. To tackle the problem, this study develops a metamaterial structure, referred to as a meta-structure, to tactically enhance the cumulative second harmonic S0 Lamb waves by converting the A0 mode components into S0 mode waves. Topology optimization is conducted to design the meta-structure, which is surface-mounted onto the structure under inspection, to achieve high-efficiency A0-to-S0 wave mode conversion. Through tuning the parameters and constraints of the optimization, the designed single-sided meta-structure breaks the structural symmetry in the thickness direction, while facilitating its practical implementation. Typical scenarios with different meta-structure materials are discussed. Numerical simulations demonstrate that the strain amplitudes of the fundamental S0 mode waves can be increased by 60% with the deployment of the meta-structure, alongside an enhancement of the second harmonic S0 mode waves at different sensing distances. Finally, the designed meta-structure is fabricated via 3D printing technique and tested experimentally on an aluminum plate subjected to thermal aging treatment for monitoring the heating-induced microstructural changes inside the structure. Experimental results confirm an increase in the wave amplitudes of the linear S0 mode waves with the assistance of the meta-structure. The developed system improves the sensitivity of nonlinear Lamb wave-based monitoring methods in characterizing material microstructural changes, which shows great promise for detecting incipient damage in practical structural health monitoring applications.

ДЖОНШЕРОВСКИЙ УНИВЕРСАЛЬНЫЙ ДИНАМИЧЕСКИЙ ОТКЛИК В ТОНКИХ ПЛЕНКАХ ПОЛИДИФЕНИЛЕНФТАЛИДА

It is known that the supramolecular structure of organic materials can have a significant effect on the conductivity of polymer films in both constant and alternating fields. In particular, the presence of associative supramolecular formations can lead to a significant increase in the local dielectric constant. At the same time, the presence of different types of supramolecular ordering can lead to the predominance of certain charge transfer mechanisms in polymer films, and, consequently, to the presence of a dependence of conductivity on the electric field strength. The degree of molecular ordering, both on the surface and in the bulk of a polymer film, can also have a significant effect on polarization. In this regard, studying the influence of the supramolecular structure on the conductivity of polymer films in an alternating electric field is an urgent task.Previously, using various methods, it was established that the supramolecular structure of films with a thickness of more than 300 nm is determined mainly by supramolecular formations of an associative structure. The structure of films with a thickness of 100 to 300 nm is determined by the mixed structure of globular and associative formations. The structure of films less than 100 nm thick is determined by supramolecular formations of a globular. It was also established by the method of thermally stimulated depolarization that three regions are observed on the dependence of the activation energy of capture centers on the thickness of the polymer film, corre- sponding to different supramolecular organizations.In this work, the dependence of the conductivity of poly (diphenylene phthalide) films in an alternating electric field in the low-frequency range from 0.1 to 106 Hz on the supramolecular structure of polymer films was studied. It was found that the type of dependence of the conductivity of polymer films on the frequency of an alternating field depends on the thickness and supramolecular structure of the polymer films, as well as the electric field strength. The applicability of the Jonsher’s model, which describes the conductivity of amorphous materials in an alternating electric field, for thin polymer films is discussed. A correlation between the power-law dependence index and the supramolecular structure of the polymer film and the influence of dipole polarization and injection of charge carriers into the bulk of the polymer film on the conductivity of the polymer film have been revealed.

The Benefit of a Multi-wedge Acoustic Black Hole at Low-frequency Mitigation

IntroductionAcoustic black holes (ABH) are capable to mitigate structural vibrations efficiently above a certain cut-on frequency. The most commonly used geometry for a flexible beam is a simple wedge following a power-law curve. A simple wedge demands large dimensions for achieving mitigation in the low-frequency range below 1000 Hz. It was shown recently by experiments and numerical simulation that a multi-wedge configuration is beneficial for realizing a compact design and still showing good performance at low frequencies.Materials and MethodsThe WKB approximation is extended for a single-wedge design. Expressions for the reflection coefficient and cut-on frequency are discussed for an arbitrary number of wedges—the suggested multi-wedge ABH.ResultsThe main benefit of the stacked multi-wedge ABH is a great improvement in performance in the low-frequency range. A numerical example highlights the successful vibration mitigation. It is shown how a multi-wedge ABH is tuned towards low-frequency in terms of cut-on frequency and reflections’ coefficient. The improved performance of a multi-wedge ABH is benchmarked against the well-established simple ABH.

Stretchable, stable, and structural color reversible enabled by mesoscopic regulation and design for flexible photonic crystal mechanical sensors

This paper reports a flexible mechanical sensor developed by combining an opal photonic crystal and a flexible medium through UV curing technology. Under the action of external force, the deformation of the flexible medium causes the change of the photonic crystal lattice constant, which leads to the displacement of the reflection peaks, thus realizing the detection of the deformation of the film. The flexible medium is mixed by photoinitiators and polymer monomers, and its mechanical properties are directly related to the mass fraction of photoinitiators and polymer monomers. The results show that the film can reach a maximum strain of about 180% when the mass fraction of photoinitiator is 3% and the volume ratio of the polymer functional monomers is 8:2. In addition, for the responsiveness test of the sensor under tensile, the results show that at 0%, 26%, and 78% of tensile strain, its structural color is blue-shifted sequentially, and its spectral peaks are 668 nm, 535 nm, and 488 nm, respectively. Finally, the sensor is applied to the detection of acoustic waves in air, and it is found that its spectral response peaks can be obtained for acoustic waves of different frequencies (250–650 Hz), and a spectral peak at 500 Hz. This flexible photon sensor has the potential to match the acoustic resistance of water. It will greatly expand the response research of ocean exploration in the low frequency range.

Microwave absorption properties of CI and E-waste based heterogenous mixtures

This work presents the study of effect of morphology of carbonyl iron, carbonyl iron-based, and e-waste-based mixtures on microwave absorption properties. Firstly, the flake shaped carbonyl iron particles and its mixture are prepared using conventional and efficient ball milling and blending method, respectively. It provides the absorption in lower frequency region. Further, the covered frequency range starts to shifts slowly towards higher frequency ranges due to the morphological changes. On the other hand, effect of complex morphology of e-waste-based mixtures are also studied. These heterogeneous mixtures are developed using the cutting mill and blending methods that can provide the absorption in higher frequency with very narrow bandwidth. In this manner, effect of morphology on single layer microwave absorption performance of developed heterogenous material is proposed. It is also explored that the developed samples cover a wider bandwidth by utilizing the multilayering technique. A three-layer absorber is designed using genetic algorithm and the results are also validated. The structural and morphological study of the developed heterogeneous materials has been done using X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) analysis. Also, rigorous study has been done on magnetic properties and Cole-Cole plots to understand the magnetic and dielectric losses respectively occurring inside the materials. The results showed wide bandwidth absorption of 11.62 GHz (≤−10 dB bandwidth) in the lower frequency region ranges from 0.5 to 12.12 GHz (i.e., L, C, and X-band). The total thickness achieved is 1.85 mm which is very compact (<2 mm). Thus, a thin and wideband microwave absorber at lower frequency range using heterogeneous morphology of developed materials is also presented. The proposed microwave absorbing materials can be potentially utilized for the shielding applications.

Pattern effect suppression of pulse signals based on pre-signal control method

By using the pre-signal light as the control light, we propose a method to suppress the transient effect of erbium-doped fiber amplifiers for low-frequency pulse signals. The pattern effect of the pulse signals within the low frequency range (400–1000 Hz) and 1550 nm band is relieved, and the optical surge coefficient Cs decreases to about 0.54 dB. Experimental results show that the proposed method has better performances in suppressing pattern effect in comparison with the conventional continuous light control scheme and higher output gain compared to the compensation pulsed light method. Our proposed pattern effect suppression approach based on the pre-signal control method is anticipated to find promising applications in the field of optical communications.

Comparison of pulsed and continuous electromagnetic field generated by WPT system on human dermal and neural cells

In recent decades, we have seen significant technical progress in the modern world, leading to the widespread use of telecommunications systems, electrical appliances, and wireless technologies. These devices generate electromagnetic radiation (EMR) and electromagnetic fields (EMF) most often in the extremely low frequency or radio-frequency range. Therefore, they were included in the group of environmental risk factors that affect the human body and health on a daily basis. In this study, we tested the effect of exposure EMF generated by a new prototype wireless charging system on four human cell lines (normal cell lines—HDFa, NHA; tumor cell lines—SH-SY5Y, T98G). We tested different operating parameters of the wireless power transfer (WPT) device (87–207 kHz, 1.01–1.05 kW, 1.3–1.7 mT) at different exposure times (pulsed 6 × 10 min; continuous 1 × 60 min). We observed the effect of EMF on cell morphology and cytoskeletal changes, cell viability and mitotic activity, cytotoxicity, genotoxicity, and oxidative stress. The results of our study did not show any negative effect of the generated EMF on either normal cells or tumor cell lines. However, in order to be able to estimate the risk, further population and epidemiological studies are needed, which would reveal the clinical consequences of EMF impact.

Changes in the electrical and viscoelastic parameters of erythrocytes in patients with manifestations of metabolic syndrome, COVID-19 convalescents, when exposed to citicoline in an in vitro experiment

Aim. To study changes in the electrical and viscoelastic parameters of erythrocytes using the method of dielectrophoresis in patients with manifestations of the metabolic syndrome who underwent COVID-19, when exposed to the drug citicoline in an in vitro experiment to reduce the severity of microcirculatory disorders.&#x0D; Materials and methods. 31 men were examined with manifestations of metabolic syndrome (50.6±9.9 years), COVID-19 convalescences, within 8 to 12 months after the disease, the diagnosis was confirmed by PCR, ELISA. The electrical and viscoelastic parameters of erythrocytes were studied by dielectrophoresis twice: the initial levels of indicators were determined and after 30 minutes of exposure with after 30 minutes of exposure to a solution of the drug Ronocyte (oral solution with the active substance citicoline sodium – 104.50 mg., which is equivalent to 100.00 mg citicoline at a concentration of 0.01 µl per 0.3 µl of red blood cell suspension in 0.3M sucrose solution (pH 7.36).&#x0D; Results. Exposure of erythrocyte suspension of patients with Ronocyte solution led to change in the levels of electrical, viscoelastic parameters: an increase in the average cell diameter (p=0.0003), the proportion of discocytes (p=0.0004), the amplitude of cell deformation at high frequencies of the electric field (p=0.000002), cell capacity (p=0.000007), the velocity of erythrocytes to the electrodes (p=0.003), dipole moment (p=0.002), polarizability at 106 and 0.5×106 Hz (p=0.000019 and p=0.0015, respectively), relative polarizability (p0.05) and, conversely, to reduce summarized rigidity (p=0.000003), viscosity (p=0.000002), electrical conductivity (p0.000001), aggregation indices (p=0.00003), destruction at frequencies of 106 Hz (p=0.003), 0.5x106 Hz (p=0.00002), 0.1×106 Hz (p0.00001), polarizability at low frequencies of the electric field (p=0.02). Under the influence of the drug, the equilibrium frequency of erythrocytes shifted to the low-frequency range compared to the initial values (p0.0000001). The revealed changes indicate an increase in the surface charge of erythrocytes, their ability to deform, and cell resistance under the action of citicoline.&#x0D; Conclusion. For the first time, the effect of the drug with the active substance citicoline, improving the rheological properties of erythrocytes, was discovered. Preparations with the active substance - citicoline should be considered promising for conducting a full-fledged clinical study to study the reduction of circulatory disorders at the microcirculatory level in patients with manifestations of metabolic syndrome who have undergone COVID-19 coronavirus infection.

Phase transitions of choline dihydrogen phosphate: A vibrational spectroscopy and periodic DFT study.

Choline dihydrogen phosphate, [Chol][H2PO4], is a proton-conducting ionic plastic crystal exhibiting a complicated sequence of phase transitions. Here, we address the argument in the literature around the thermal properties of [Chol][H2PO4] using Raman and infrared microspectroscopy. The known structure of the low-temperature crystal, which contains the anti-conformer of [Chol]+ and hydrogen-bonded dimers of anions, was used to do periodic density functional theory calculations of the vibrational frequencies. Raman spectra indicate that the solid-solid transition at 20 °C is linked to a conformational change to the gauche [Chol] conformer with a concurrent local rearrangement of the anions. The distinct bands of lattice modes in the low-frequency range of the Raman spectra vanish at the 20 °C transition. Given the ease with which metastable crystals can be produced, Raman mappings demonstrate that a sample of [Chol][H2PO4] at ambient temperature can contain a combination of anti- and gauche conformers. Heating to 120 °C causes continuous changes in the local environment of anions rather than melting as suggested by a recent calorimetric investigation of [Chol][H2PO4]. The monotonic change in vibrational spectra is consistent with earlier observations of a very small entropy of fusion and no abrupt jump in the temperature dependence of ionic conductivity along the phase transitions of [Chol][H2PO4].

Monocular vision-based dynamic calibration method for determining the sensitivities of low-frequency tri-axial vibration sensors.

Low-frequency vibrations exist widely in the natural environment and in human activities. Low-frequency tri-axial vibration sensors are enormously applied in the fields of seismic monitoring, building structure health monitoring, aerospace navigating, etc. Their sensitivity calibration accuracy directly determines whether their applications can work reliably. Although the laser interferometry recommended by the International Standardization Organization (ISO) is commonly used to achieve the vibration calibration, it suffers from the shortages of low-frequency range, high cost, low efficiency, and limited applicable environment. In this study, a novel monocular vision-based dynamic calibration method is proposed, which determines the whole sensitivities of tri-axial sensors by the monocular vision method to accurately measure the spatial input excitation. This method improves the calibration performance by eliminating the installation error and enhancing calibration efficiency via decreasing reinstallations. The experimental results compared with the laser interferometry demonstrate that the investigated method can obtain similar calibration accuracy in the range of 0.16-2 Hz with more efficiency. The corresponding maximum relative deviations of X-, Y-, and Z-axial sensitivities were approximately 2.5%, 1.8%, and 0.4%. In addition, the maximum relative standard deviation of the investigated method was only about 0.3% in this range.

Evaluation of microwave square ring metamaterial-based resonator for glucose detection

This study presents a biosensor working at a frequency of 3.5 GHz, which is designed as a square ring metamaterial resonator. This study aimed to evaluate the impact of blood amount on the metamaterial-based resonator sensor’s sensitivity. The structure was constructed using Rogers-RT5880 material, with an overall area of 85.71 mm × 85.71 mm2. The simulation of the design involved modelling the blood samples using Debye 1st-order equations. The empirical results observed a noticeable shift towards a lower frequency range in the response and changes in the magnitude, corresponding to an increase in the blood sample’s glucose concentration and thickness. Following this, the experiment was designed to corroborate the simulated results. The sensor achieved the highest sensitivity of 0.23 dB per 100 mg/dl change in glucose level when the thickness of blood was 0.1 mm. It was concluded from the results that the increase in the volume of blood increases the sensor’s sensitivity. However, a trade-off mark is necessary in which an optimum sensitivity is achieved with blood volume as minimum as possible so that a noninvasive biosensor can be designed.

Subwavelength acoustic topology frequency band regulation based on symmetric site-space folded resonant cavities

Acoustic topological insulators, as a type of acoustic metamaterial, possess special acoustic wave manipulation capabilities. However, an acoustic topological insulator based on Bragg scattering requires its lattice constant to be equivalent to the wavelength. This means that constructing acoustic topological insulators efficiently in the low-frequency range is a challenge. To this end, this paper proposes a method to construct sub-wavelength acoustic topological insulators by adding spatially folded resonant cavities at symmetric locations. It can easily reduce unidirectional transmission frequency bands with topological protection to subwavelength scales. On this basis, it is even possible to realize effective control of the unidirectional transmission band over a great range by adjusting the length parameter of the folded resonant cavity. The control range can reach more than 4000Hz. Experimental results from finite element simulations further verify that this approach does not affect the topologically protected edge states and the topologically unidirectional acoustic transmission properties. This work provides a method for the construction of low-frequency acoustic topological insulators, as well as an efficient method for the accurate regulation of unidirectional transmission frequency bands over a wide range of frequencies.

Prediction of the sound pressure response in an enclosed cavity with sound absorbent walls using the CMA and AMA methods

The sound pressure response in an enclosed cavity with sound absorbent walls is predicted using the classical modal analysis (CMA) method and the asymptotic modal analysis (AMA) method. The sound absorbing material is represented as an equivalent fluid with frequency dependent bulk material properties. The equivalent fluid properties can be obtained from either impedance tube test data or based on micro-scale Biot material properties. In the low frequency range, the CMA method is implemented to include the frequency dependent material properties. In the medium and high frequency ranges, when modal density is high, the frequency dependence effects become cumbersome using CMA. The AMA method has been developed as an asymptotic extension of the CMA method for the mid- and high-frequency ranges and is extended here to incorporate the frequency dependence of an equivalent fluid properties of the sound absorbing materials. An enclosed rectangular box subjected to loudspeaker excitation is used to evaluate the effect of absorption materials using the CMA method for the low-frequency range and the AMA method for the mid- and high-frequency ranges. Test data have also been obtained for comparisons of the CMA method in the low frequency range. Using these procedures, the CMA and AMA methods can be applied to represent absorbent materials over a wide frequency range for enclosure architectural design.

The acoustics of absorbers comprising a flexible perforated membrane backed by a stack of granular material

It has been found that when a layer of activated carbon partially fills the space behind a finite, edge-constrained, tensioned impermeable membrane, the absorption peaks due to the modal response of the membrane can be significantly enhanced in the low frequency range. In the present work, the modeling aspects of the latter work have been extended to allow the membrane to be both tensioned and flexurally stiff, and furthermore, to be micro-perforated, thus expanding the treatment design space. Second, the particle layer behind the membrane is modeled by using a two-dimensional finite difference implementation of the Biot poro-elastic theory which then accounts for the interaction of the particle layer and walls that contain it: i.e., the solid phase of the particle stack itself is allowed to exhibit modal behavior in the radial direction. The interaction of the membrane nearfield and the particle stack, which creates a nearfield damping effect, is also fully captured. Finally, the model accounts for the hierarchical porosity of activated carbon. The model has been verified by comparison with measurements and it has been found that strikingly high levels of low frequency absorption can be realized by appropriate optimization of the membrane and particle stack properties and geometry.

Unsteady large-scale wake structure behind levitated free-stream-aligned circular cylinder

The relationships between characteristic large-scale wake structures appearing behind a free-stream-aligned circular cylinder are investigated and discussed from the velocity field obtained by wind tunnel tests. The tests were conducted under a supportless condition using a magnetic suspension and balance system and stereo PIV measurements at a Reynolds number of $3.46\times 10^4$ . The velocity fields were analysed with a modal decomposition combining azimuthal Fourier decomposition and proper orthogonal decomposition. The wake behind the free-stream-aligned circular cylinder with three different fineness ratios of 1.0, 1.5 and 2.0 was investigated, and the wake structures in a non-reattaching flow formed by the cylinder at a fineness ratio of 1.0 are mainly discussed in the present study. Four characteristic large-scale wake structures of the recirculation bubble pumping, azimuthal shear mode, large-scale vortex shedding and streaks are identified and mainly focused on in the present study. The state of the vortex shedding is classified into three: anticlockwise/clockwise circular and flapping patterns. Each state has a relationship with the azimuthal shear mode and it tends to appear when the state is circular. Furthermore, from the analysis of the relationship between modes, the recirculation bubble pumping is found to be related to the vortex shedding position in the radial direction and the strength of the streaks. Particularly, analysis of causality shows that the recirculation bubble pumping is affected by them in the low-frequency range.

Vibroacoustic metamaterial for enhanced Sound Transmission Loss with variable frequency range designed for serial production

Recently, vibroacoustic metamaterials have been broadly investigated, especially for noise and vibration mitigation. By creating a band gap effect in flexural wave propagation in a base element, metamaterials improve its vibroacoustic parameters in low and mid frequency range while preserving low mass and structure dimensions. While the foundational assumptions and lab validations highlight the advantages of these metamaterials, the practical application of these structures in real-world scenarios remains a challenge. The main aspect that is widely investigated is achieving maximum effectiveness while maintaining the simplicity of geometry to optimize mass production costs. This work presents a vibroacoustic metamaterial design with geometry adapted to serial production using injection molding. The proposed geometry allows for adjusting the effective frequency range of the structure after the production process. Due to the distinctive configuration of the elements and the grouping of unit cells, the design facilitates the generation of broadband and multi-band structures as well. Numerical simulations were employed to assess the impact of the proposed metamaterial on Sound Transmission Loss and other vibroacoustic parameters. Experimental validation of prototype effectiveness was conducted through Sound Reduction Index measurements in a diffuse field.

Phase transformation and plasmonic damping study for semi-solid ionic polymeric hydrogel system at higher temperature and low radio frequency

This article represents the findings regarding the phase transitions exhibited by a polymeric hydrogel material composed of sodium polyphosphate-polyethylene glycol. These transitions play a crucial role in the generation of ionic plasmons and the manifestation of surface plasmon resonance (SPR) with dielectric permittivity damping within the polymer electrolyte system of the hydrogel. Usually, SPR has been observed in electron-conducting systems within an optical frequency range. However, here SPR is observed in an ionic system within a lower radio frequency range of 104-10 (Parwati et al., 2024) 77 Hz for temperatures exceeding 80 °C. The mechanism responsible for permittivity damping can be elucidated by considering the accumulation of ionic charges at the interface between the electrode and the electrolyte, coupled with a high degree of charge absorption following the Drude model. A power law has been used to describe the resonance that occurs between the applied DC frequency and the motion of charge carrier ions, thus confirming the presence of free ionic motion within the hydrogel matrix. tan δ shows significant energy absorption further substantiating permittivity damping, which transitions from positive to negative values.

Towards extraordinary sound absorption using coupled resonances

In this paper, we provide an overview of recent advancements in novel sound absorption designs, predominantly based on optimized coupling between resonances. First, we present a sound absorption panel design capable of achieving high absorption in the low-frequency broadband range (50–63 Hz, one-third octave band). This panel demonstrates an average absorption coefficient of approximately 93%, all while maintaining a thickness of 15.4 cm (equivalent to 1/45 of the wavelength at 50 Hz). Transitioning from the one- port system, we delve into the realm of the two-port system, introducing an ultra-sparse structure for flow-free sound absorption. This structure exhibits near-perfect absorption (∼99%), and this absorption capability is achieved when the spatial period of monopole–dipole resonators is close to one working wavelength (95% wavelength). These developments signify significant strides in sound absorption technology, presenting innovative solutions with enhanced efficiency and performance across various frequency ranges and environments.

An analysis and retrofit of the acoustics at Image Creators Health and Beauty Salon

This paper discusses the analysis and retrofit of the acoustics in a high-volume beauty salon in Severna Park, Md. The major issues in what was intended to be a serene environment are reverberation times of 1–1.68 s in the mid-to upper frequency range and Background noise levels ranging from 73.4 to 64.6 dB in the mid to low frequency range. Employee and customer complaints include ear pain and tinnitus due to prolonged exposure to high background levels, heightened stress, vocal strain, headaches and poor speech intelligibility. Existing analysis and the acoustical retrofit resolution will be demonstrated.