Sound Frequency Range Research Articles

Facile fabrication of 3D-printed cellulosic fiber/polylactic acid composites as low-cost and sustainable acoustic panels

This work presents a green, cost-effective and eco-friendly strategy to reduce noise pollution by developing biopolymer-based 3D-printed acoustic panels. We successfully fabricated two series of composites by varying the weight percentage (wt%) of cellulose fibers of water hyacinth (WH) and pineapple leaf (PAL), with polylactic acid (PLA) as the matrix via the heat-press method. All samples were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Physico-mechanical properties, including hardness, tensile, and impact strength, were improved with increasing fiber loading. Filaments of 1 wt% water hyacinth fibers (WHFs) in PLA (1 WHF/PLA) and 1 wt% pineapple leaf fibers (PALFs) in PLA (1 PALF/PLA) were prepared and tested for 3D printability. The sound absorption coefficients (α) of the 3D-printed panels were investigated from 500 to 5000 Hz sound frequency range. The 3D-printed 1 WHF/PLA and 1 PALF/PLA acoustic panels achieve a maximum α (α-max) of 0.55 and 0.83 at 5000 and 4000 Hz, respectively, featuring the first work to report α-max > 0.5 at low fiber loadings in the high-frequency sound range. The tensile strength of the 3D-printed versions is significantly higher than non-3D-printed counterparts and commercial acoustic absorbers. Our data suggest the prepared 3D-printed panels are excellent candidates for acoustic applications at high-frequency noises. This study exhibits a facile, environmentally benign and sustainable approach to construct highly efficient and mechanically robust biopolymer-based 3D-printed sound-proof panels, which have promising potential as green engineering materials. Interestingly, this research also proposes a mitigation technology for the freshwater invader, Eichhornia crassipes (water hyacinths).

Effect of scatterer shape, opening angle and periodicity on sound attenuation by local resonating sonic crystal

Noise Control has become critical and demanding task for acoustic engineers due to continuous Technological developments in construction, transportation, and industries. These developments have raised the level of low frequency noise in densely populated areas. Unfortunately, there cannot be sufficient noise reduction with traditional acoustic materials. However, new research has shown that the manipulation of sound waves and drastic reduction in sound transmission can be possible using periodic structure known as Sonic Crystals (SnC). This study describes the eigenfrequency analysis to investigate the effect of different shapes, periodicities, and opening angles of scatterers in a Local resonating Sonic Crystal (LRSnC). The Block-Floquet boundary condition is applied to the unit cell of the LRSnC, using the Finite Element Method to study the complex acoustic wave interactions throughout the structure. An acoustic module has been applied to find the band gap and to simulate transmission loss spectra in COMSOL Multiphysics. Results show that shape, opening angle and periodicity effect the band gap and transmission loss significantly. Based on these results, it is possible to develop advanced SnC with a wider band gap and higher sound attenuation in the lower sound frequency range by carefully considering these factors.

Proteins required for stereocilia elongation during mammalian hair cell development ensure precise and steady heights during adult life

The hair bundle, or stereocilia bundle, is the mechanosensory compartment of hair cells (HCs) in the inner ear. To date, most mechanistic studies have focused on stereocilia bundle morphogenesis, and it remains unclear how this organelle critical for hearing preserves its precise dimensions during life in mammals. The GPSM2-GNAI complex occupies the distal tip of stereocilia in the tallest row and is required for their elongation during development. Here, we ablate GPSM2-GNAI in adult mouse HCs after normal stereocilia elongation is completed. We observe a progressive height reduction of the tallest row stereocilia totaling ~600 nm after 12 wk in Gpsm2 mutant inner HCs. To measure GPSM2 longevity at tips, we generated a HaloTag-Gpsm2 mouse strain and performed pulse-chase experiments in vivo. Estimates using pulse-chase or tracking loss of GPSM2 immunolabeling following Gpsm2 inactivation suggest that GPSM2 is relatively long-lived at stereocilia tips with a half-life of 9 to 10 d. Height reduction coincides with dampened auditory brainstem responses evoked by low-frequency stimuli in particular. Finally, GPSM2 is required for normal tip enrichment of elongation complex (EC) partners MYO15A, WHRN, and EPS8, mirroring their established codependence during development. Taken together, our results show that the EC is also essential in mature HCs to ensure precise and stable stereocilia height and for sensitive detection of a full range of sound frequencies.

Improving Sound Insulation in Low Frequencies by a Three-Component Cladding Acoustic Metamaterial Panel

In this paper, a three-component cladding acoustic metamaterial panel with good sound insulation effect in the low-frequency range is proposed. The sound transmission loss of metamaterial panels under different structural configurations and different material parameters is investigated by combining finite element simulation calculations with experimental research. The results show that the closer the center of gravity of the scatterer is to the substrate, the better the stability of the resonance unit, the wider the range of effective sound isolation frequencies, and the higher the degree of normalization. The filling rate of the scatterer is maintained at about 0.5 to obtain a better sound insulation effect. At the same time, choosing lower density materials for the substrate and metal materials with high density and high modulus of elasticity for the scatterer can maximally widen the bandgap and allows for low-frequency sound insulation below 600 Hz. This approach improves the low-frequency sound insulation efficiency of acoustic metamaterials. The results provide important explanations and references for a deeper understanding of the sound insulation mechanism and the effects of different parameters on sound insulation.

Акустический пограничный слой твёрдой абсолютно теплопроводной поверхности

The paper presents the analysis results of formation theoretical descriptions of an acoustic boundary layer near solid absolutely thermally conductive surface, obtained by G. Kirchhoff and L.D. Landau. In both cases, the acoustic boundary layer is formed by inhomogeneous viscous and thermal waves in the wall layer of a liquid medium in contact with the surface of a solid body, from which a plane traveling sound wave is reflected. Based on the analysis, conclusions can be drawn: the analyzed problem solutions are physically sound, independent and complementary to each other. During the formation of an acoustic boundary layer, viscous and thermal waves are excited synchronously in pairs. Inside the acoustic boundary layer, each pair of inhomogeneous waves propagates towards each other. Inhomogeneous waves originate on parallel surfaces that limit the volume of the acoustic boundary layer. The analysis of the process of transformation of heat waves into additional one-dimensional inhomogeneous waves, the appearance of which in the boundary layer was predicted by G. Kirchhoff. It is shown that when interacting with the surface of the body of a traveling sound wave in the sound frequency range, these waves do not affect the formation of the boundary layer. The expressions allowing for a numerical estimation of the heat dissipation power density in the boundary layer are refined. A formula has been obtained that allows us to determine the proportion of the energy of the sound wave that is absorbed in the acoustic boundary layer. In practice, the results obtained in the article can be used, for example, in aeroacoustics to assess the dissipative properties of solid surfaces.

The Average Sound Energy Spectrum Produced by a Single Raindrop

The characteristics of underwater acoustic radiation generated by a single raindrop impacting the water surface play a fundamental role in the study of rainfall noise. However, the underwater sound signal generated by a single raindrop has great randomness in the amplitude of sound pressure, frequency range and energy size, so that the uncertainty of the sound energy spectrum curve of a single raindrop is relatively large. In this paper, by generating artificial rainfall containing only one size of raindrop, the acoustic radiation generated by artificial rainfall composed of about 136,000 raindrops with an equivalent diameter of 0.9 mm was measured by reverberation method. A smooth, continuous sound energy spectrum of single raindrop covering the full frequency band is obtained.

Tunable Acoustic Properties Using Different Coating Systems on Resonance Spruce Wood

AbstractThe study investigates the effect of the type of varnish and the number of layers on some acoustic properties of the resonance spruce in combination with the changes produced in some physical, morphological, and chemical properties of wood. In addition to color changes and surface chemistry, the surface roughness and morphology are modified by the thickness of the varnish film, 10 layers being optimal from this point of view, as well as the oil‐based finish. The sound absorption coefficient increases with the number of varnish layers and varies with the sound frequency range, varnish type, and wood quality, all contributing to the acoustic tunability. For example, for a sound frequency of 1.5 kHz, it is observed that the oil‐based varnish with 5 and 10 layers contributes to a full sound, while the alcohol varnish, due to a lower absorption coefficient for this frequency, can lead to some nasal sounds. Applying more than 10 layers of varnish does not improve the sound performance as it will soften the sound in an oil‐based finish and make the sound too sharp in the case of alcohol–varnished wood.

Planar piezoelectric metamaterials: Sound transmission and applicable frequency range in oblique incidence

Frequency limit and applicable frequency range of planar piezoelectric metamaterials connected to external circuits have not been well defined in estimating the sound transmission loss. This article extends the classical transfer matrix method for use in evaluating the sound transmission of thin-plate piezoelectric metamaterials in oblique incidence. Using the Kirchhoff thin plate theory, a modified transfer matrix method that takes factors of external circuits into consideration is developed for attenuation and control of acoustic waves. Several vibro-acoustic analytical models are compared, including the Kirchhoff thin plate theory, the Reissner–Mindlin thick plate theory and the theory of wave propagation in elastic solids. These theories are used to determine the dispersion relation, coincidence and transition frequency of thin and thick plate theories in analysing piezoelectric acoustic metamaterials, alongside a validation using the finite element method. Then acoustic properties of piezoelectric plates connected to passive external circuits are studied parametrically with both dimensional and dimensionless variables based on an equivalent Kirchhoff plate approximation. The findings show that external electrical impedance alone can be used to adjust the resonance frequency over a broad range and thereby control sound transmission loss. This provides considerable flexibility in modifying the acoustic properties of the piezoelectric metamaterial in comparison to traditional, fixed-structure metamaterials. The study indicates a straightforward and powerful analytical approach for the optimization of acoustic insulation using thin-plate piezoelectric metamaterials.

Control of flow separation over an aerofoil by external acoustic excitation at a high Reynolds number

The effectiveness of acoustic excitation as a means of flow control at high Reynolds number turbulent flows is investigated numerically by using improved delayed detached eddy simulations (IDDES). Previous studies on low Reynolds number laminar flows have shown that acoustic excitation can substantially suppress flow separation for specific effective frequency and amplitude ranges. However, the effect of acoustic excitation on higher Reynolds number turbulent flow separation has not yet been explored due to limitations on appropriate fidelity computational methods or experimental facility constraints. Therefore, this paper addresses this research gap. A NACA0015 airfoil profile at 1 × 106 Reynolds number based on the airfoil chord length is used for the investigations. Acoustic excitation is applied to the baseline flow field in the form of transient boundary conditions at the computational domain inlet. A parametric study revealed that the effective sound frequency range shows a Gaussian distribution around the frequency of the dominant disturbances in the baseline flow. A maximum of ∼43% increase in lift-to-drag ratio is observed for the most effective excitation frequency F+=1.0 at a constant excitation amplitude of Am=1.8%. The effect of excitation amplitude follows an asymptotic trend with a maximum effective excitation amplitude above which the gains are not significant. A fully reattached flow is observed for the highest excitation level considered (Am=10%) that results in ∼120% rise in airfoil lift-to-drag coefficient. Overall, the findings of the current work demonstrate the higher Reynolds number effectiveness of acoustic excitation on separated turbulent flows, thereby paving the way for application in realistic flow scenarios observed in aircraft and gas turbine engine flow fields.

The sensitivity of mechanoelectrical transduction response phase to acoustic overstimulation is calcium-dependent

The Mechanoelectrical transduction (MET) channels of the mammalian hair cells are essential for converting sound stimuli into electrical signals that enable hearing. However, the impact of acoustic overstimulation, a leading cause of hearing loss, on the MET channel function remains poorly understood. In this study, I investigated the effect of loud sound-induced temporary threshold shift (TTS) on the transduction response phase across a wide range of sound frequencies and amplitudes. The results demonstrated an increase in the transduction response phase following TTS, indicating altered transduction apparatus function. Further investigations involving the reduction of extracellular calcium, a known consequence of TTS, replicated the observed phase changes. Additionally, reduction of potassium entry confirmed the specific role of calcium in regulating the transduction response phase. These findings provide novel insights into the impact of loud sound exposure on hearing impairment at the transduction apparatus level and highlight the critical role of calcium in modulating sound transduction. Considering that over 1 billion teenagers and young adults globally are at risk of hearing loss due to unsafe music listening habits, these results could significantly enhance awareness about the damaging effects of loud sound exposure.

Round-robin tests of the different types of sensors for floor impact sounds and vibrations

Recently, floor impact noise monitoring system was introduced for residents to control making noises spontaneously using sound and vibration sensors. The present study aims to investigate the performance and characteristics of various current using sound and vibration sensors which can be eventually compatible with the floor impact noise monitoring system. For measurements of sound sensors, 7 sound microphones were used including 2 condenser types, 4 dynamic types, and 1 electro condenser type. Also, 6 vibration meters were used including 2 MEMS types, 2 Piezo types, and 2 spring types. Sound levels were measured in a semi-anechoic chamber using white noise in the frequency range from 63 Hz to 12.5 kHz. Vibrations were measured using high density wooden panel with an impact ball in the frequency range from 16 Hz to 4 KHz. Round-robin tests were done to confirm the exact performances of all the sensors under same condition. As a result, it was found that dynamic type microphones show the most similar response characterization in comparison with the reference condenser microphone especially in the air-borne sound frequency range from 250 Hz to 2 KHz. Also, it was found that spring type vibration meters show the most appropriate characterization at 63 Hz, most critical structure-borne sound frequency. Thus, the results drawn from the round-robin tests could be used for floor impact noise monitoring systems with the benefit of both economy and performance.

Orthogonal matching pursuit algorithm based on weighted cosine similarity for sound source localization

Abstract Compressive sensing overcomes the limitations of the Nyquist criteria and is one of the most widely used compressive sensing reconstruction algorithms. Orthogonal matching pursuit (OMP) algorithm is simple, in terms of hardware implementation, and has high computational efficiency. However, the OMP algorithm exhibits poor identification performance for low-frequency sound sources and results in large localization deviations when the mesh spacing of the focus plane is small. In this study, a novel atom selection criterion based on weighted cosine similarity was proposed to improve the OMP algorithm for sound source localization and characterization. This method replaces the original inner product criterion to measure the correlation between the column vectors of the sensing matrix and the residuals, which addresses the atom selection error caused by the high correlation between atoms. Numerical simulations and experimental results show that the proposed method has a stronger anti-noise interference capability and higher accuracy for sound source identification with fewer sampling points, particularly in low-frequency and low signal-to-noise ratio environments. Compared to other OMP algorithms, the proposed method improves the performance of the OMP algorithm in sound source localization and widens the sound frequency range. This study is valuable for achieving highly accurate sound source localization and reducing measurement costs in practical applications.

WaveNet-based approximation of a cochlear filtering and hair cell transduction model

Computational auditory models are important tools for gaining new insights into hearing mechanisms, and they can provide a foundation for bio-inspired speech and audio processing algorithms. However, accurate models often entail an immense computational effort, rendering their application unfeasible if quick execution is required. This paper presents a WaveNet-based approximation of the normal-hearing cochlear filtering and inner hair cell (IHC) transduction stages of a widely used auditory model [Zilany and Bruce (2006). J. Acoust. Soc. Am. 120(3), 1446–1466]. The WaveNet model was trained and optimized using a large dataset of clean speech, noisy speech, and music for a wide range of sound pressure levels (SPLs) and characteristic frequencies between 125 Hz and 8 kHz. The model was evaluated with unseen (noisy) speech, music signals, sine tones, and click signals at SPLs between 30 and 100 dB. It provides accurate predictions of the IHC receptor potentials for a given input stimulus and allows an efficient execution with processing times up to 250 times lower compared to an already optimized reference implementation of the original auditory model. The WaveNet model is fully differentiable, thus, allowing its application in the context of deep-learning-based speech and audio enhancement algorithms.

Fabrication of one-step shape memory gradient sound absorber with wrinkled inner wall and closed-pore structure

Plastic foam sound-absorbing material is of great significance to improve indoor sound environment. However, since the preparation of foamed material is fundamentally induced to form a homogeneous pore structure, the sound absorption frequency range is relatively narrow, limiting the sound absorption performance to a great extent. In order to improve the sound absorption performance in a wide frequency range, this work designed the combination of macro-porous gradient foam (MGF) and closed-pore resonator, introduced part of polyimide (PI) components based on the one-step free foaming method of polyurethane foam (PUF), and proposed a straightforward route to prepare basic polymer gradient foam. Through the arrangement and combination of different bubble holes, the sharp hole structure and the Helmholtz resonance structure were constructed by analogy. Importantly, the internal structure of the foam system was reorganized under the action of surface tension due to the inward collapse of the viscous bubbles during the process of bursting, resulting in the formation of wrinkled structures and small bubbles, which enhanced the resonant sound absorption at lower frequencies. In 200–6400 Hz, the MGF1 sample had the highest sound absorption capacity, with a cavity size range of 8.27–4.14 mm and the ability to absorb 90% of the acoustic wave above 1100 Hz. In addition, MGF samples also exhibited heat insulation behavior (0.047–0.061 W/(m·K)), shape memory, and energy absorption capacity. This gradient compound resonance structure satisfies the convenience of process manufacturing and high-efficiency sound absorption performance, which is essential for the wide application of plastic foam sound-absorbing materials.

Low‐Intensity Sensitive and High Stability Flexible Heart Sound Sensor Enabled by Hybrid Near‐Field/Far‐Field Electrospinning

AbstractLow‐cost and wearable heart sound sensors can facilitate early detection and monitoring of cardiovascular and respiratory diseases. Such sensors are currently limited by either the complexity of fabrication processes or low sensitivity and reliability for weak signal detection. Here, a hybrid near‐field/far‐field electrospinning approach is demonstrated that enables low‐cost fabrication and optimization of triboelectric heterostructures for heart sound sensing. Specifically, by combining the far‐field produced highly polarized and porous polyvinylidene difluoride network for triboelectric electrification and near‐field patterned polyurethane grid spacers for vibration enhancement and charge trapping, the greatly improved sensor output at the heart sound frequency (50–150 Hz) and intensity (<80 dB) range, demonstrating record high sensitivity of 7027 mV Pa−1 and low detection limit of 47 dB. The sensor exhibits excellent stability under both sudden physical disturbance and long‐term cycling stress, showing no degradation during 7 h of continuous operation. It is demonstrated that the sensor can be integrated with apparel and capture high‐quality heart sound signals at all five diagnostic auscultation points and distinguish characteristic heart sound patterns caused by different cardiovascular diseases.

Experiments on the dynamic Poisson's ratio of PUR foams

AbstractPolyurethane (PUR) foams are used in various industrial applications, including vibration damping and noise reduction. Because the effective mechanical properties are needed for the engineering design process, this work presents a method to measure the dynamic Poisson's ratio for the typical range of sound frequencies. A hydraulic pulse testing machine is used to apply the harmonic displacement excitation of the cylindrical specimens for 1 − 100 Hz. The analysis of the time‐dependent deformation data is based on video recordings of a high‐speed camera and a specially derived image processing algorithm.For the Poisson's ratios of the measured foams no significant frequency dependence was found. For PUR foam with an open‐cell or mixed‐cell microstructure the dynamic Poisson's ratio is approximately 0.3. Poisson's ratios of about 0.4 were measured for PUR foams with a high density and a closed‐cell microstructure.

Reuse of Textile Waste in the Production of Sound Absorption Boards

Textile waste is formed in various stages, from the preparation of raw materials to the utilisation of textile products. One of the sources of textile waste is the production of woollen yarns. During the production of woollen yarns, waste is generated during the mixing, carding, roving, and spinning processes. This waste is disposed of in landfills or cogeneration plants. However, there are many examples of textile waste being recycled and new products being produced. This work deals with acoustic boards made from waste from the production of woollen yarns. This waste was generated in various yarn production processes up to the spinning stage. Due to the parameters, this waste was not suitable for further use in the production of yarns. During the work, the composition of waste from the production of woollen yarns was examined-namely, the amount of fibrous and nonfibrous materials, the composition of impurities, and the parameters of the fibres themselves. It was determined that about 74% of the waste is suitable for the production of acoustic boards. Four series of boards with different densities and different thicknesses were made with waste from the production of woollen yarns. The boards were made in a nonwoven line using carding technology to obtain semi-finished products from the individual layers of combed fibres and thermal treatment of the prepared semi-finished product. The sound absorption coefficients in the sound frequency range between 125 and 2000 Hz were determined for the manufactured boards, and the sound reduction coefficients were calculated. It was found that the acoustic characteristics of soft boards made from woollen yarn waste are very similar to those of classic boards or sound insulation products made from renewable resources. At a board density of 40 kg/m3, the value of the sound absorption coefficient varied from 0.4 to 0.9, and the noise reduction coefficient reached 0.65.

Sound Range AE as a Tool for Diagnostics of Large Technical and Natural Objects.

Application of acoustic emission of the sound frequency range is under consideration. This range is of current interest for the diagnostics of the stability of mountain slopes, glaciers, ice covers, large technical constructions (bridges, dams, etc.) as well as for the detection of rock deformation anomalies preceding earthquakes. Acoustic sensors, which can be used to record and to determine the directivity of acoustic emission of the sound frequency range, are under consideration. The structure of the system for acoustic emission recording, processing and analysis is described. This system makes it possible to determine the direction to the acoustic emission source using one multi-component sensor. We also consider the algorithms for detection of acoustic emission pulses in a noisy background, and for the analysis of their structure using the Adaptive Matching Pursuit algorithm. A method for the detection of the direction to an acoustic emission signal source based on multi-component sensors is described. The results of application of sound range acoustic emission for the detection of the intensification of rock deformations, associated with earthquake preparation and development in the seismically active region of Kamchatka peninsula, are presented.

Polarization features of Bi12SiO20:Cr and Bi12SiO20:Mn crystals

The effect of impurity ions and polarization conditions on the dielectric characteristics and polarization features of Bi12SiO20 crystals doped with Cr and Mn ions is studied by dielectric spectroscopy in the sound frequency range and by thermoactivation spectroscopy in the temperature range 280 ÷ 800 K. The mechanisms of the observed phenomena are discussed at the atomic level.

Effect of sound excitation on the flow field and convection heat transfer around a cylinder

The combination of experiment and numerical simulation, sound frequency and sound pressure level on the flow field, and heat transfer around a cylinder with two flow patterns are investigated. Flow patterns are periodic laminar flow (L3, Re0 = 100) and wake transition (TrW2, Re0 = 300), respectively. Sound frequency range f = 100–1000 Hz, and sound pressure level range SPL = 127–145 dB. Based on the influence of acoustic characteristics on the viscous boundary layer and thermal boundary layer of cylindrical wall, constructed a functional relationship between convection heat transfer and sound wave frequency and sound pressure level. Influenced by the acoustic action, the flow field force around the cylinder, the vortex street structure, the vortex size, and the length of the wake area may be changed. Acoustic action flow field excitation fluid particle velocity amplitude increased. As the sound pressure level increased, the amplitude of the fluid mass vibration velocity increased. From the experimental results, it can be seen that for the acoustic frequency effect, the heat transfer coefficient increases with increasing sound frequency. For the particle velocity amplitude effect, as the acoustic Reynolds number increases, the heat transfer coefficient increases and is 2.3 times higher than that without acoustic disturbance in the wake turning flow regime. In comparison with numerical and experimental results, the error is less than 15%, which meets the actual requirements of the project. It has been shown that sound waves can enhance the convective heat transfer around a cylinder in the cross-flow.