A design of the sonic crystal (SC), called the gradient-based sonic crystal (GBSC), that uses the gradient of properties of the SC array is proposed as an improvement over the traditional design of SCs. The gradient of properties is obtained by changing the resonator dimensions and the distance between them throughout the array instead of keeping them uniform. Because of this non-uniformity, the supercell

Sound radiation from thin metal plates has consistently been recognized as a severe noise problem. One of the most popular approaches to suppressing this noise is applying viscoelastic layers, also called free layer damping (FLD), on the plate surface, which can damp the structural motion and minimize the radiated sound. The thickness of the FLD is an important parameter. It needs to be optimized for

Acoustic attenuation of a hybrid sonic crystal made with periodic cylindrical scatterers and cascaded porous panels in a broad frequency range is endeavoured in this paper. It is observed via simulations that, the insertion loss (IL) of hybrid configuration is larger than the summation of IL of individual contributors such as periodic scatterers and parallel porous panels in post first Bragg resonance

The number of research papers dealing with vibration-based condition monitoring has been exponentially growing in recent decades. As a consequence, one may identify some trends that emerge from this vast literature. The present paper delineates a methodology that can be recognized in several research works, which is rooted in a succession of three stages. The first stage embodies a linear transform

This paper discusses trends in condition monitoring of modern offshore wind turbines. First an overview is given of design changes that have been made over the years to large offshore wind turbines and how this resulted in novel opportunities from a monitoring perspective. Similarly, the evolution in data source availability is discussed. From these opportunities, some ongoing research activities in

This paper provides an overview of the recent advances made in the field of fault diagnosis of industrial machines operating under variable speed conditions. First, the shortcomings of the traditional techniques in extracting reliable fault information are laid down, followed by a discussion on the different approaches adopted to overcome these issues. Next, these approaches are discussed by categorizing

With the huge success of applying deep learning (DL) methodologies to image recognition and natural language processing in recent years, researchers are now keen to use them in the machine condition monitoring (MCM) context. There are numerous papers in applying various DL techniques, such as auto-encoder, restricted Boltzmann machine, convolutional neural network and recurrent neural network, to MCM

A simplified finite element method (FEM) simulation method has been established and validated for analyzing the sound absorption mechanism of structures with periodic axisymmetric cavities. Combined with genetic algorithm, the simplified FEM method is used to optimize the sound absorption coefficient of the structure containing periodic cylindrical cavities and variable cross section cavities. The

Helmholtz resonator is considered and widely accepted as a basic acoustic model in engineering applications and research. In this paper, the normal incidence sound absorption characteristics of series and parallel configurations of Helmholtz resonators is studied analytically, numerically and experimentally. The proposed analytical model for series configuration of HRs comprises of Johnson–Champoux–Allard

With the huge success of applying deep learning (DL) methodologies to image recognition and natural language processing in recent years, researchers are now keen to use them in the machine condition monitoring (MCM) context. There are numerous papers in applying various DL techniques, such as auto-encoder, restricted Boltzmann machine, convolutional neural network and recurrent neural network, etc

To expand the spatial and temporal scales of passive acoustic monitoring of animals, automatically detecting target sounds among noises with similar acoustic properties is essential but challenging. In particular, the classification of tonal vocalisations and tonal noise remains a universal problem in bioacoustics research. The vocalisations of dugong, which is an endangered marine mammal that inhabits

The cascade’s response function can be used to effectively deal with the unsteady response of the interaction between the harmonic turbulence and the cascades. Based on this function, this paper presents the formulas for the stator broadband and tonal noises, whose inflow models are different from each other. The broadband noise comes from the impact of the random turbulence wave in the rotor wake

Long-term data of underwater passive acoustic monitoring (PAM) collected from two sites of pygmy blue whale presence within Australia, the continental shelf off Portland (38.5° S, 141.2° E) and the Perth Canyon (32° S, 115° E) were analysed to compare the acoustic behaviour of eastern Indian Ocean pygmy blue (EIOPB) whales. Pygmy blue whale song detection was consistently higher at the Perth Canyon

Machine health condition monitoring is evidently a crucial challenge nowadays. Unscheduled breakdowns increase operating costs due to repairs and production losses. Scheduled maintenance implies taking the risk of replacing fully operational components. Human expertise is a solution for an outstanding expertise but at a high cost and for a limited quantity of data only, the analysis being time-consuming

In this paper, the two-zone sound field reproduction problem is investigated with a newly proposed method. The aim of the two-zone reproduction problem is to achieve sound field reproduction in the bright zone while keeping the sound field energy in the dark zone as low as possible. The main difference between the proposed method and the conventional method is that the sound field control in the dark

In this paper, the authors discuss about the future challenges of condition monitoring in an industrial context. One of the authors is Line Manager at Data Processing & Analytics for Equipment, Industry 4.0 & MES Products division of Tetra Pak Packaging Solutions S.p.A., a multinational company that approached condition monitoring and diagnostics fifteen years ago. So far, they have gained experience

The wind industry has seen tremendous growth during the past two decades, with the global cumulative installation capacity reaching more than 650 gigawatts by the end of 2019. Despite performance and reliability improvements of utility-scale wind turbines over the years, the industry still experiences premature component failures, leading to increased operation and maintenance (O&M) costs. Among various

Experimental studies were conducted at a hemi-anechoic chamber to investigate the effectiveness of trailing-edge (TE) serration designs for reducing aerodynamic noise of a propeller. The propeller noise was measured under different speeds in both the vertical and horizontal directions. The thrust force produced by the propeller was also measured at rotational speeds. The flaplet, concave and sawtooth

Vibration signals collected from machines can contain rich machine degradation information, such as impulsiveness and cyclo-stationarity. In the field of machine condition monitoring (MCM), quantification of impulsiveness has attracted many researchers’ interests because impulsiveness often indicates an occurrence of incipient faults. Impulsiveness-based health indicators (HIs) (e.g., Gini index, kurtosis

This study aims to examine the influence of colour exposure on noise annoyance. Previous studies in the literature have focused mostly on the effects of colour exposure on loudness judgements; however, due to the cognitive nature of multisensory perception, the influence of colour on noise annoyance also needs to be investigated. Our experiments were designed to administer non-information-carrying

The parabolic approximation has been used extensively for underwater acoustic propagation and is attractive because it is computationally efficient. Widely used parabolic equation (PE) model programs such as the range-dependent acoustic model (RAM) are discretized by the finite difference method. Based on the idea of the Pad\(\acute{\text {e}}\) series expansion of the depth operator, a new discrete

Proper detection and monitoring of cracks are crucial when evaluating the health of equipment and structures because of the catastrophic failures that can occur if they evolve without control. Among the group of nondestructive tests (NDT), acoustic emissions (AE) emerge as the most used technique for this purpose. This is due to its high sensitivity to low-energy events, which allows the incipient

Despite the progress made in the last decades in the field of machine condition monitoring, there are still cases where the current state of the art is not enough and new technologies and advanced analysis methods are required to prevent unexpected failures. One example is planetary gearboxes (PGs), which are one of the main components of mechanical transmission systems in heavy-duty machines such

An experimental method in a real-working condition was conducted to collect acoustic emission (AE) signals emitted from cylinders of a large two-stroke low-speed marine diesel engine. Measurements were performed in an axial direction of the cylinder in medium-frequency (20–80 kHz) and high-frequency (100–900 kHz) ranges and in a vertical direction only in the medium-frequency range under two engine

The paper presents a retrospective and prospective view of noise mapping strategy followed across the globe as a diagnostic tool for controlling the noise pollution in urban cities. The concept of noise mapping is primitive in India and thus developing the noise maps is really a great challenge for big metropolitan cities of India. The paper discusses the benefits associated, input parameters required

The supra-aural headphone concentrates the sound in the listener’s ears, so the loudspeaker sound is confined to the cavity between the pinna and the headphone casing. It is then directed toward the tympanic membrane through the ear-canal. The high-quality sound requirement of supra-aural headphone on one side and space limitation on the other prompted this research. Similarly, inherent sound leakages

Despite intensive management, the increasing conflict between humans and saltwater crocodiles in places such as Queensland, Australia, has led to the investigation of alternative techniques to improve public safety. The reliability of digital video surveillance systems (DV) placed above water and multi-beam sonar (sonar) placed under water to detect and monitor saltwater crocodiles was tested in a

Traditional acoustic liners used in nacelles and fan ducts include a perforated face sheet bonded to a honeycomb core. A tunable acoustic liner with a piezoelectric substrate is developed to overcome the shortages of current liner such as unchangeable structure and uncontrollable bandwidth. After the piezoelectric panel deformed under the driving voltage, the resonant chamber changed, and the resonant

This study addresses the problem of source depth discrimination in the context of shallow-water acoustics. From the perspective of beam pattern correlations, a discriminating characteristic quantity, which implies the information of source depth, is presented and defined as the difference factor of the vertical beam pattern. In applying the proposed difference factor for source depth discrimination

Acoustic emission (AE) technique has been merged to a promising method for structural health monitoring in non-destructive technique. So an analysis of the AE signal is becoming a very important research component. In this paper, an algorithm is developed for detection of the crack signal among different noise signals since the AE signal is also generated by several means like any impact or rubbing

Effective low-frequency and large-scale noise reduction are crucial in industrial applications. Conventional passive methods lack the effective low-frequency performance, and existing hybrid methods are costly to realize large-scale absorption. Hence, an effective and simply actuated solution for low-frequency and large-scale absorption is urgently needed. In this study, the low-frequency (100–500 Hz)

An accurate head-related transfer function can improve the subjective auditory localization performance of a particular subject. This paper proposes a deep neural network model for reconstructing the head-related transfer function (HRTF) based on anthropometric parameters and the orientation of the sound source. The proposed model consists of three subnetworks, including a one-dimensional convolutional

Freshwater hydroacoustic surveys are frequently performed with small research boats. Thus, the transducer, usually fixed on a pole on the side of the boat, could be misaligned with the horizontal axis (i.e., the lake surface). Given that fish acoustic responses are strongly directional, the transducer angle could induce attenuation of their backscattering strengths. To test the influence of a small

Nowadays, the sound source localization is widely applied in various fields, with a focus on arrays or algorithms. Meanwhile, acoustic metasurfaces have recently attracted enormous interest in material science. This paper proposed a kind of piezoelectric acoustic metasurface, whose structure is theoretically proved to be useful in sound field orientation or sound source localization. The metasurfaces

In the context of eatery places, it is important that people concentrate and focus on the smells and tastes of their food and drinks to ensure that they are satisfied with their meals, as this influences the positive behavior of the intent to return and can prompt them to recommend an eatery place to others later. A higher level of noise may distract people from having a fine dining experience and

A new method of head-related transfer function (HRTF) personalization was built to optimize new user matching in the HRTF database to enhance 3D virtual hearing. The method of modified sparse representation (MSR) treated the HRTF personalization for an incomer as the task of finding similar subjects in the HRTF database with sparse representation (SR) of the incomer’s anthropometric features under

Restoration of historical buildings should be carried out without giving damage to the existing historical building, and material selections should be determined in accordance with the historical building structure. In addition to the selection of materials compatible with the historical structure, the selection of materials that can improve the interior acoustic quality of the space is one of the

The article A Review of the Potential Impacts of Wind Turbine Noise in the Australian Context, written by John Laurence Davy, Kym Burgemeister, David Hillman & Simon Carlile, was originally published electronically on the publisher’s internet portal on 27 June 2020 without open access.

Aiming at the problem that it is difficult to accurately predict the aerodynamic noise in the safety valve exhaust process, a new numerical simulation method that comprehensively considers the dipole sources and the quadrupole sources is proposed. The RNG k–ε model is used to simulate the steady-state flow fields, LES numerical method is used to simulate the transient flow, and then the unsteady disturbances

The engine compartment is the main source of automobile noise. In this paper, based on the study of the noise characteristics of the engine compartment, the relationship model is established between engine speed and noise frequency, and an active noise reduction method is proposed based on the adaptive least mean square (LMS) algorithm. Because the adaptive change of the convergence factor is controlled

With the rapid advancement of technology of unmanned aerial vehicles (UAVs), security and safety of military and civil infrastructure have been jeopardized. By exploiting the unreliable capabilities of radar to detect low-flying UAVs with small radar cross section, they can be utilized for malicious purposes, e.g., unauthorized surveillance. To detect UAVs, therefore, various other techniques including

To research the effect of blade outlet angle on acoustics of marine centrifugal pump, the unsteady numerical simulation analysis of the four models is carried out and the dipole source of pump shell is extracted. The constraint modal of pump, interior sound pressure level (SPL), exterior acoustic directivity and sound power level are obtained. The results show that five and six SPL peaks appear at

The acoustic performance of multilayered structures (MLSs) can be identified by experiments and calculation models that use commercially available software. This paper presents both an experimental method and data processing techniques that can be used for obtaining the acoustic characteristics of MLSs. During the described experiments, three types of MLSs with different structures are designed and

Continuum topology optimization is an effective way to reduce vibration and noise of vibro-acoustic coupling system. However, the high computation time required for calculating the vibro-acoustic responses during topology optimization is a major obstacle for practical applications. In this paper, a novel symmetric method of vibro-acoustic system matrix is proposed, and a new model reduction method

Fitness culture has significantly grown since the nineteenth century. In the recent decade, the gym and fitness industry have thrived in many countries. The construction of gymnasiums has increased dramatically, and fitness centres have become one of the most common spaces in mix-used buildings around the world. There are a significant number of gyms located relatively close to residential areas, some

This manuscript describes a range of technical deliberations undertaken by the authors during their work as members of the Australian Government’s Independent Scientific Committee on Wind Turbines. Central to these deliberations was the requirement upon the committee to improve understanding and monitoring of the potential impacts of sound from wind turbines (including low frequency and infrasound)

One of the applications of the acoustic reflectometry technique is to study the layered media structures such as soil, snow. The issues of acoustic reflectometry system to study the layered media structures related with using non-ideal components are given in this paper. It has been demonstrated that there are several artifacts present in the acoustic reflectometry analysis in practice. The paper presents

The classical transfer path analysis (TPA) method has become a standard measurement method. It has high accuracy but remains a time-consuming and complex measurement, which limits its application in industry. The operational transfer path analysis (OTPA) method is known for its high efficiency; however, the accuracy of this method for industrial application is controversial. To separate the intake

A statistical energy analysis (SEA) model of a 510 l capacity refrigerator is used to calculate the sound pressure level generated in a reverberation room. This is a reliable indicator of the vibroacoustic performance of the refrigerator, and it is in some countries as a pre-commercialization test. The main contributions of the SEA model are the characterization of the refrigerator structure (three-layer:

To solve the beamforming performance degradation problem of the towed linear array caused by the shape distortion, we propose a robust beamforming way for distorted towed linear array. The proposed method basically uses the segmented processing, which can be divided into 3 steps. Firstly, towed linear array is divided into sub-arrays. Then, the weights of sub-arrays are obtained and outputs of beamforming

This work examines experimentally the absorption characteristics of empty plastic water bottles. It focuses on the three common sizes of bottles widely available in the Saudi market (1500, 600 and 330 ml). Measurements were performed according to ISO 354 and ISO 9613-1 standards in the reverberation chamber. Three systematic groups of measurements were performed, each of which examined only one of

Structural finite element coupled with the conjugated infinite element method is an efficient numerical technique for solving the acoustic radiation problem due to the vibration of underwater objects. However, for large complex structures, the total acoustic mesh would become very large if the artificial boundary is too far away from the structural wetted surface. Thus, the calculation time can become

Discrete singular convolution (DSC) algorithm is an accurate dynamic analysis method for single structures. However, vibration analysis of connected structures via the DSC method is limited to step beams and plates. This paper extends the applicability of the DSC method in handling acoustic transmission lines composed of several duct elements with different diameter ratios. Connections of elements

Noise may cause hearing damage and delayed growth and development in newborns in neonatal intensive care units. Hence, it is necessary to reduce noise in these environments. Training and use of visual signs have been investigated as the interventional strategies with the aim of reducing noise level and exposure in neonatal intensive care units. This quasi-experimental study (before and after design)

The source parameters of Irrawaddy dolphins’ echolocation click in the Bay of Brunei were estimated. Analysis of eight parameters shows that the Irrawaddy dolphins produce broadband echolocation clicks with mean click duration of 21.1 ± 7.2 μs. The clicks had a mean peak-to-peak apparent source level (ASLpp) of 201.2 ± 7.3 dB re 1 μPa (N = 350), a mean peak frequency of 116.5 ± 15.2 kHz, a mean centroid

Manual bone drilling in orthopedic surgical operations may cause injury to patient tissues if the drill bit continues to progress after exiting the bone. In this study, a new bone breakthrough detection algorithm based on acoustic emission (AE) signal analysis has been developed to minimize temporary and permanent injuries that can be caused by surgeon-controlled surgical drills. Three parametric estimation

In this work, we develop an optimization approach to optimize the distribution of porous material layer inside cavity. The optimization seeks to improve the absorbing effects of the porous material, decreasing the noise level at regions of interest or increasing the sound energy dissipated by the porous material. To achieve the preset optimization aim, two different objective functions are accordingly