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Limitations in traditional manufacturing methods currently employed in the production of acoustic devices, restricts the development of design led performance improvements. These devices are used to control sound energy and are commonly employed for tailoring room acoustics. solid freeform fabrication allows the production of acoustic structures more complex than traditionally manufactured devices. This paper aims to focus on a novel absorber based on destructive interference, considering performance, design and manufacture.

Selective laser sintering has been used in the investigation of the performance and manufacturing possibilities and limitations of a novel destructive interference absorber. Validation of the absorber performance is benchmarked against a conventional resonant absorber and compared to published results. The implications for acoustic devise design, the advances and limitations in manufacture using solid freeform fabrication techniques and potential applications are discussed.

An original absorber design has been shown to exhibit comparable acoustic absorption to that of a traditional solution. The nature of the geometry of the novel absorber demonstrates that the design flexibility afforded by solid freeform fabrication processes holds potential for applications incorporating new types of acoustic absorber. The use of solid freeform fabrication has demonstrated its potential to the application of acoustics, and has highlighted limitations due to post‐processing, material strength and the precision of the selectivity process.

Solid freeform fabrication techniques enable a new family of specifically engineered acoustic absorbers capable of incorporating performance benefits over conventional absorbers.

This paper focuses on room acoustic applications, the creation of high performance, conformal absorbers, applicable to a wide range of applications within the aerospace, automotive and construction industries, where space, weight and performance are key criteria.

Informed by acoustic design standards, the built environments are designed with single reverberation times (RTs), a trade-off between long and short RTs needed for different space functions. A range of RTs should be achievable in spaces to optimise the acoustic comfort in different aural situations. This paper proclaims a novel concept: Intelligent passive room acoustic technology (IPRAT), which achieves real-time room acoustic optimisation through the integration of passive variable acoustic technology (PVAT) and acoustic scene classification (ASC). ASC can intelligently identify changing aural situations, and PVAT can physically vary the RT.

A qualitative best-evidence synthesis method is used to review the available literature on PVAT and ASC.

First, it is highlighted that dynamic spaces should be designed with varying RTs. The review then exposes a gap of intelligently adjusting RT according to changing building function. A solution is found: IPRAT, which integrates PVAT and ASC to uniquely fill this literature gap.

The development, functionality, benefits and challenges of IPRAT offer a holistic understanding of the state-of-the-art IPRAT, and a use case example is provided. Going forward, it is concluded that IPRAT can be prototyped and its impact on acoustic comfort can be quantified.

The purpose of this paper is to develop a novel electromagnetic-based acoustic energy harvester (EH) for the application of wireless autonomous sensors.

The developed acoustic EH comprises a Helmholtz resonator (HR), a suspension system that consists of a flexible membrane and a permanent magnet, a couple of coils and a coil holder. Furthermore, the HR, used in the harvester, is designed for a specific resonant frequency based on simulation carried out in COMSOL Multiphysics®.

The developed harvester is tested both in lab under harmonic sound pressure levels (SPLs) and in real environment under random SPLs. In lab, when exposed to 100 dB SPL, the harvester generated a peak power of 212 µW. Furthermore, in real environment in vicinity of electric generator, the harvester produced an output voltage of about 110 mV collectively from its both coils.

In this paper, a novel geometric configuration for electromagnetic-based acoustic EH is proposed. In the developed harvester, two coils are placed in it to achieve enhanced electrical output from it for the first time.

The purpose of this paper is to developing a kind of acoustic metamaterial with wide frequency band especially in low frequency region. At the same time, its the tunability of sound insulation frequency is achieved.

A three-dimensional (3D) acoustic metamaterial consisting of rigid frame, spherical attachment and thin film is proposed. The material parameters and the effect of the attachment hole on the forbidden band are investigated by finite element simulation. The sound insulation effect of the structure is validated by the combination of simulation and experiment.

The results show that the elastic modulus of the structural material determines the initial frequency of the forbidden band of the proposed 3D acoustic metamaterials. The lower the elastic modulus of the structural material, the lower the initial frequency of the forbidden band. The material parameters of the frame mainly affect the initial frequency of the first forbidden band, and the material parameters of the attachment will affect both the initial and termination frequency of the first forbidden band. Holes in the attachments reduce the band gap width. The characteristic curve moves down with the increase of subtracted mass.

The findings may greatly benefit the application of the acoustic metamaterials in the fields of sound insulation and noise reduction.

This acoustic metamaterial structure has excellent sound insulation performance. At the same time, the single cell structure can be assembled into any shape. The structure can achieve sound selective filtering and combination control.

The capability of microparticle/objects patterning in the three-dimensional (3D) printing structure could improve its performance and functionalities. This paper aims to propose and evaluate a novel acoustic manipulation approach.

A novel method to accumulate the microparticles in the cylindrical tube during the 3D printing process is proposed by acoustically exciting the structural vibration of the cylindrical tube at a specific frequency, and subsequently, focusing the 50-μm polystyrene microparticles at the produced pressure node toward the center of the tube by the acoustic radiation force. To realize this solution, a piezoceramic plate was glued to the outside wall of a cylindrical glass tube with a tapered nozzle. The accumulation of microparticles in the tube and printing structure was monitored microscopically and the accumulation time and width were quantitatively evaluated. Furthermore, the application of such technology was also evaluated in the L929 and PC-12 cells suspended in the sodium alginate and gelatin methacryloyl.

The measured location of pressure and the excitation frequency of the cylindrical glass tube (172 kHz) agreed quite well with our numerical simulation (168 kHz). Acoustic excitation could effectively and consistently accumulate the microparticles. It is found that the accumulation time and width of microparticles in the tube increase with the concentration of sodium alginate and microparticles in the ink. As a result, the microparticles are concentrated mostly in the central part of the printing structure. In comparison to the conventional printing strategy, acoustic excitation could significantly reduce the width of accumulated microparticles in the printing structure (p < 0.05). In addition, the possibility of high harmonics (385 and 657 kHz) was also explored. L929 and PC-12 cells suspended in the hydrogel can also be accumulated successfully.

This paper proves that the proposed acoustic approach is able to increase the accuracy of printing capability at a low cost, easy configuration and low power output.

The purpose of this paper is to evaluate the application of an acoustic micro‐imaging (AMI) inspection technique in monitoring solder joints through lifetime performance and demonstrate the robustness of the monitoring through analysis of AMI data.

Accelerated thermal cycling (ATC) test data on a flip chip test board were collected through AMI imaging. Subsequently, informative features and parameters of solder joints in acoustic images were measured and analysed. Through analysing histogram distance, mean intensity and grey area of the solder joints in acoustic images, cracks between the solder bump and chip interface were tracked and monitored. The results are in accord with associated Finite Element (FE) prediction.

At defective bumps, the formation of a crack causes a larger acoustic impedance mismatch which provides a stronger ultrasound reflection. The intensity of solder joints in the acoustic image increase according to the level of damage during the ATC tests. By analysing the variation of intensity and area, solder joint fatigue failure was monitored. A failure distribution plot shows a normal distribution pattern, where corner joints have the lowest reliability and are more likely to fail first. A strong agreement between AMI monitoring test data and FE prediction was observed, demonstrating the feasibility of through lifetime monitoring of solder joints using AMI.

The paper indicates the feasibility of the novel application of AMI inspection to monitor solder joint through lifetime performance non‐destructively. Solder joints' real life conditions can be tracked by an AMI technique, hence solder joint fatigue failure cycles during the ATC tests can be monitored and analysed non‐destructively.

Adequate protection from external noise and vibration, adequate control of noise emission to keep the neighbours happy, control of office services plant and equipment to avoid poor working conditions, optimum layout, finishes and fittings for good acoustics and appropriate sound insulation, special acoustic applications — this article, by Jeffrey Charles of Bickerdike Allen Partners, is concerned with the technical know‐how necessary for good acoustic conditions in and around the office, and the actions the facilities manager can and should take to achieve them.

The acousto-ultrasonic approach is used for propagating stress waves through different configurations of CORTEN steel specimens. The propagated waves are recorded and analysed by piezoelectric sensors. The purpose of the study is to study the characteristics of the CORTEN steel by analysing the propagated waves.

To investigate the attenuation in acoustic wave propagation due to the corrosion formation in CORTEN steel specimens and to train a neural network model to classify the attenuated acoustic waves automatically.

Due to the corrosion formation in CORTEN steel specimens, attenuation is observed in amplitude, energy, counts and duration of the propagated waves. When the waves are analysed in their time-frequency characteristics, attenuation is observed in their frequency and spectral energy.

The corrosion formation in CORTEN steel can automatically be analysed by using the acousto-ultrasonic approach and the trained deep learning neural network.

One of the authors has already formulated the sensitivity analysis for a coupled structural‐acoustic system and applied the method in order to obtain modal sensitivities and modal frequency response sensitivities for the sound pressure level at peak frequency points. However, for the development of a vehicle, not only the reduction of peak frequency level but also that of integral of noise for a specified frequency range is desired. For investigating this it is considered effective to use sensitivities of integrated sound pressure level for a specified frequency range. Thus a “sound pressure level integral” has been developed, which is the integrated value of sound pressure level, and further “sensitivity of sound pressure level integral”. Shows how an integral analysis process is performed, and how vibration and noise can be reduced.