Revealing sound-induced motion patterns in fish hearing structures in 4D: A standing wave tube-like setup designed for high-resolution time-resolved tomography

Modern bony fishes possess a high morphological diversity in the auditory structures and their auditory capabilities. Yet, our knowledge of how the auditory structures such as the otoliths in the inner ears and the swim bladder work together remains elusive. Gathering experimental evidence on the in-situ motion of fish auditory structures while avoiding artifacts caused by surgical exposure of the structures has been challenging for decades. Synchrotron radiation-based tomography with high spatio-temporal resolution allows to study morphofunctional issues non-invasively in an unprecedented way. We therefore aimed to develop an approach that characterizes the moving structures in 4D (= three spatial dimensions+time). We designed a miniature standing wave tube-like setup to meet both the requirements of tomography and those of tank acoustics. With this new setup, we successfully visualized the motion of isolated otoliths and the auditory structures in zebrafish (Danio rerio) and the glass catfish (Kryptopterus vitreolus).

A hybrid method of predicting the acoustical properties of multi-layered materials

Many numerical and measuring approaches are widely used in predicting and analysing the acoustic performances of laminated materials for noise control applications. However, numerical methods generally require a set of non-acoustic parameters, and the measuring methods are not available for exceedingly thick materials. The main aim of this article is to address a hybrid approach of evaluating the normal incidence sound transmission loss and absorption coefficients of multi-layered materials. This method is performed with some special parameters that contain the sound transmission and reflection coefficients of each sub-layer of a multi-layer specimen and can be measured by a standing wave tube system. The accuracy and feasibility of the present method are validated by the experimental and numerical comparisons between different methods and samples. Moreover, this present approach can be applied as a numerical tool of estimating the acoustical behaviours of multi-layered structures in noise control treatments, such as automotive, building and aerospace industries.

Analysis and Identification of Nonlinear Acoustic Damping in Miniature Loudspeakers

Nonlinear acoustic damping is a key nonlinearity in miniature loudspeakers when the air velocity is at a high amplitude. Measurement of nonlinear acoustic damping is beneficial for predicting and analyzing the performance of miniature loudspeakers. However, the general measuring methods for acoustic impedance, such as the standing-wave tube method or the impedance tube method, are not applicable in this scenario because the nonlinear acoustic damping in miniature loudspeakers is coupled with other system nonlinearities. In this study, a measurement method based on nonlinear system identification was constructed to address this issue. The nonlinear acoustic damping was first theoretically analyzed and then coupled in an equivalent circuit model (ECM) to describe the full dynamics of miniature loudspeakers. Based on the ECM model, the nonlinear acoustic damping was identified using measured electrical data and compared with theoretical calculations. The satisfactory agreement between the identification and theoretical calculations confirms the validity of the proposed identification method.

Phase structures, loss, storage, damping, voice-absorption, and mechanical properties: NCB/BWZT/RTV

The objective of this work is to characterize the effect of NCB(Nano-carbon black)on the comprehensive performances and micro, chemical and phase structures of NCB/BWZT/RTV composite [BWZT is Ba (W1/2Cu1/2)O3-Pb0.98Sr0.02 (Mg1/3Nb2/3) 0.275(Ni1/3 Nb2/3)0.10(Zr0.25Ti0.375) O3 and, RTV is Room Temperature Vulcanizing silicone rubber.]. Composites with damping-absorption performances and storage-loss behaviors based on RTV, BWZT and, NCB as conductive agent were fabricated employing three steps methods of ball-milling, three-roller milling and pressing. The effects of NCB and its amount on storage, loss and damping properties were investigated by the method of DMTA and, absorption and mechanical performances are measured by the methods of standing wave tube and TG separately. The micro, chemical and phase structures of composites are characterized by SEM, XRD and IR. The results indicated that both doping of NCB and the combination of BWZT and RTV can be proposed to improve greatly the comprehensive performance of RTV matrixes and, there would be more excellent comprehensive properties in NCB/BWZT/RTV composites with amount of 4 wt. %.-6wt. % for NCB as d33 of 81 pC/N, storage modulus of 25003MPa, loss modulus of 398MPa, damping coefficient of 0.07–0.12, and absorption coefficients of 0.45–0.55 with the difference of frequency in the range of 400-1600Hz. Also, the lattice growth of BWZT is found showing strong dependences on the contents of NCB and, the absorption and damping performance of composites on frequency and temperature separately.

Performance Characterization of Broad Band Sustainable Sound Absorbers Made of Almond Skins

In order to limit the environmental impact caused by the use of non-renewable resources, a growing research interest is currently being shown in the reuse of agricultural by-products as new raw materials for green building panels. Moreover, the European directives impose the goal of sustainability supporting the investigation of passive solutions for the reduction of energy consumption. Thus, the promotion of innovative building materials for the enhancement of acoustic and thermal insulation of the buildings is an important issue. The aim of the present research was to evaluate the physical, acoustical, and thermal performances of building panels produced by almond skin residues, derived from the industrial processing of almonds. In this paper different mix designs were investigated using polyvinyl acetate glue and gum Arabic solution as binders. Air-flow resistivity σ and normal incidence sound absorption coefficient α were measured by means of a standing wave tube. Thermal conductivity λ, thermal diffusivity α, volumetric heat capacity ρc were measured using a transient plane source device. Finally, water vapor permeability δp was experimentally determined using the dry cup method. Furthermore, a physical characterization of the specimens in terms of bulk density ρb and porosity η allowed to study the correlation existing between the binder and the aggregates and the consequent acoustical and hygrothermal behavior occurring on the different mix designs. The achieved results suggested the investigated materials comparable to the main products currently existing on the market.

Finite-Element Method for Calculating the Sound Field in a Tank with Impedance Boundaries

In this paper, a finite-element method for calculating the sound field in a water tank with impedance boundaries is proposed based on the theory of standing waves in a tube. The equivalent acoustic impedance of the tank walls is calculated by establishing a three-dimensional axisymmetric virtual standing-wave tube in finite-element software, whereupon boundaries with that impedance are used as the tank boundaries. Since the impedance is the property of the material itself, the calculated impedance value can be used for the calculation of the three-dimensional sound field. The sound field due to a point source in a glass tank is calculated using the proposed method, the correctness of which is assessed experimentally. By comparing the experimental and numerical results, the proposed method is shown to be correct.

A study on MEMS vector hydrophone and its orientation algorithm

Purpose The problem of port and starboard ambiguity will exist when only utilize the vector or scalar parameters. Meanwhile, the amplitude-phase error between the vector and scalar can also cause this problem. In this paper, a compound MEMS vector hydrophone which contains cilia vector microstructure and piezoelectric ceramic tube has been presented to solve the problem. Compared with traditional MEMS vector hydrophone, the compound MEMS vector hydrophone can realize the measurement of sound pressure and vibration velocity simultaneously. Design/methodology/approach A compound MEMS vector hydrophone has been presented. The unipolar directivity of the combined signal which combine the acoustic pressure and vibration velocity is used to achieve the direction of arrival (DOA). This paper introduced the working principle and the target detection mechanism of the compound vector hydrophone. The amplitude and phase error are analyzed and corrected in the standing wave tube. After that, the authors use beam-forming algorithm to estimate the DOA. Findings The experimental results in the standing wave tube and the external field verified the vector hydrophone's directional accuracy up to 1 and 5 degrees, respectively. Practical implications The research of compound vector hydrophone plays an important role in marine acoustic exploration and engineering applications. Originality/value This research provides a basis for MEMS hydrophone directivity theory. The compound vector hydrophone has been applied in the underwater location, with a huge market potential in underwater detection systems.

Identification of Acoustic Characteristic Parameters and Improvement of Sound Absorption Performance for Porous Metal

Porous metal is widely used in the fields of sound absorption and noise reduction, and it is a critical procedure to identify acoustic characteristic parameters and to improve sound absorption performances. Based on the constructed theoretical sound absorption model and experimental data, acoustic characteristic parameters of the porous metal were identified through the cuckoo search identification algorithm, and their reliabilities were certified through comparing with these labeled parameters and further experimental validation. By adding the microperforated metal panel in front of the porous metal, a composite sound-absorbing structure was formed, which aimed to improve the sound absorption performance of the original porous metal by optimizing the parameters. Finite element simulation and a standing wave tube measurement were conducted to validate the effectiveness and practicability of the optimal composite sound-absorbing structure. Consistencies among theoretical predictions, simulation results, and experimental data proved the effectiveness of the identification and optimization method. When the target frequency ranges were 100–1000 Hz, 100–2000 Hz, 100–3000 Hz, and 100–4000 Hz. Actual average sound absorption coefficients of the optimal composite structures were 0.5154, 0.6369, 0.6770, and 0.7378, respectively, which exhibited the obvious improvements with a tiny increase in the occupied space and a small addition in weight.