Quiet Zone Research Articles

Canceling Crosstalk Sound in Bone Conduction Hearing: An Accelerometer-Based Approach.

Bone conduction hearing aids offer a unique solution for people with conductive hearing loss, providing a direct transmission of sound to the cochlea. However, a common issue called "crosstalk" can occur, where sound intended for one ear is received by the opposite ear via bone conduction, affecting the ability to localize sound sources and understand speech in noise. To address this issue, we investigated whether canceling "crosstalk" at an accelerometer located on the mastoid would create a "quiet zone" that reaches the cochlea in the inner ear. Our evaluation with individuals having normal hearing abilities showed that their hearing thresholds were improved with crosstalk cancellation than without. These results indicate that although designed to cancel "crosstalk" at the mastoid, the cancellation still reached the cochlea, making it perceptible and potentially beneficial for those with conductive hearing loss.

An Analytical Model for Understanding Active Directivity Noise Control with Near-Field Error Sensing

Recent research shows that a directional quiet zone from near to far field can be created with a near-field microphone array. However, there is no systematic theoretical analysis of this error-sensing strategy. In this paper, an analytical model of the angular spectrum of point sources in the free field is proposed, based on which the near-field error-sensing strategy for active directivity noise control can be quantitively analyzed. It is found that the noise reduction in the far field is determined by the angular spectrum estimation error of both the primary and secondary sources. The impacts of the error microphone array configuration, sound source position, and target direction on the estimation error of angular spectrum are investigated. Finally, experiments were conducted in the anechoic chamber to validate the impact of the location of the secondary source.

A high‐performance dual‐polarized corrugated horn for a compact antenna test range system

AbstractA high‐performance dual‐polarized horn antenna for a 5G millimeter wave compact antenna test range system (CATR) is proposed in this article. The feed antenna is mainly composed of a double‐ridged waveguide junction orthomode transducer (OMT), mode converter, and corrugated horn antenna. Among them, the OMT is the key device for the feed antenna to achieve dual polarization characteristics, and adopts a modular design method to apply the multi‐section impedance transformer in the vertical and horizontal polarization channels with good transmission characteristics. The corrugated horn antenna generates a symmetrical radiation pattern mainly in six corrugated slots. The proposed dual‐polarized corrugated horn antenna impedance matching bandwidth (VSWR < 2) is 24–50 GHz. Moreover, the measured gain is 10–12 dBi, and the measured cross‐polarization level is less than −30 dB within the operating frequency range. Meanwhile, the half‐power beamwidth radiation pattern in the whole operating band has a good symmetry and the beamwidth in both E‐ and H‐plane remains stable. As a practical application, the designed antenna is used as the feed of the CATR system. The measured results show that the amplitude distribution in the quiet zone (QZ) is within ±1 dB, the phase distribution is within ±8°, and the cross‐polarization isolation is better than 27 dB. The performance of the QZ is conducive to the use of the CATR system.

Efficient Synthesis of Concentric-Rings Plane Wave Generators

In this paper, we present an efficient method for synthesizing sparse plane wave generators (PWGs) based concentric ring arrays. In particular, we introduce a novel circularly-polarized ring source whose field on a near-field surface can be represented using only three scalar functions. Using this representation, we can simplify the synthesis, reducing substantially its computational complexity, which can be easily handled using an ordinary office PC. After using the ring sources to identify the position and excitation of the PWG elements, we can employ discrete linearly polarized sources as feeds or use different kinds of radiators. Some numerical simulations validate the proposed approach, which can obtain planar and volumetric quiet zones with good polarization purity.

Synthesis of Near-Field Arrays Based on Electromagnetic Inner Products

Near-field antennas have been successfully adopted in several wireless applications. To exploit the high reconfigurability of array antennas, multiple synthesis techniques for arrays operating in the near-field region have been proposed. Building upon previous works on eigenmode expansions of the radiated fields, two synthesis methods for the excitations of near-field arrays based on the definition of an inner product on the electromagnetic fields are investigated: the "maximum norm" and "minimum error field norm" methods. The "maximum norm" method computes the array excitations that maximize either the active power flow through a target surface or the electric/magnetic energy stored in an assigned volume, depending on the adopted inner product. The performance of the maximum active power flow method is compared with the one of the simpler conjugate phase method. Furthermore, the limit solution achieved when the target surface reaches the far-field region is compared against the "maximum Beam Collection Efficiency" method. The "minimum error field norm" method allows to synthesize a given target field. As an example, the latter method is used to find the optimal excitation of a Plane Wave Generator with a spherical quiet zone. The effectiveness and performance of the discussed synthesis methods are validated through numerical simulations.

An adaptive constrained multi-channel active noise control filter design approach using convex cone optimization

In current practical active noise control (ANC) applications, solutions to three main technical challenges need to be sought: the requirement of a stable controller when acoustic feedback paths exist, a larger quiet zone, and adaptation to a time-varying environment. The imposed controller stability constraints can significantly increase the computational requirements and negatively impact the adaptation of ANC filters in real time. Multi-channel systems are usually needed if a larger quiet zone is required while the coupling between different channels can greatly lower the convergence rate of adaptive algorithms. In the current work, a multi-channel adaptive constrained ANC filter design method is proposed. The recently proposed convex cone formulation for ANC design is adopted to reduce the computational time of solving the constrained ANC filter design problem. The optimal filter coefficients are then redesigned continuously using convex optimization when the environment is time-varying. The experimental result shows that, compared with the traditional leaky FxLMS method, the proposed method has a faster convergence rate and a better steady-state noise control performance.

The Analysis and Verification of IMT-2000 Base Station Interference Characteristics in the FAST Radio Quiet Zone

In this study, we aim to analyze the electromagnetic interference (EMI) regarding the Five-hundred-meter Aperture Spherical radio Telescope (FAST) caused by base stations in the International Mobile Telecommunications-2000 (IMT-2000) frequency band. By analyzing the frequency bands used by the transmitting and receiving devices and the surrounding environmental parameters and utilizing an approach to predicting radio wave propagation loss that is based on deterministic methods, we conclude by comparing the predicted received power at the FAST with its interference protection threshold. Our analysis demonstrates that, currently, only 55.31% of IMT-2000 base stations in the FAST radio quiet zone (RQZ) meet the protection threshold. Additionally, this article verifies the applicability and accuracy of the radio wave propagation model used in the research based on field strength measurements. Overall, this study provides valuable insights for improving the electromagnetic environment surrounding FAST and reducing the EMI caused by mobile communication base stations. It also provides corresponding analysis methods and useful suggestions for analyzing electromagnetic radiation interference in other radio telescopes.

Global noise reduction in free-field conditions by using active noise-controlling casings

Active noise control (ANC) methods have been extensively used for reducing the noise level over the past decade. In particular, in the range of low frequencies they can effectively reduce the noise level higher than passive control methods. However, except in some special cases, in ANC only local zones of quiet are obtained. In this paper one of such exceptions is investigated—an active noise-controlling casing. More specifically, a noise source is placed inside the casing. Casing vibrations are actively controlled to achieve global noise reduction in free-field conditions. The global noise reduction is obtained using the Switched Error FXLMS algorithm and using error signals from error microphones located at appropriate points around the casing. It is shown that selected microphone array configurations can provide global noise reduction in free-field conditions. Performance of this approach is experimentally verified in a laboratory room with an exemplary acoustic treatment.

An Ultra-Wideband Plane Wave Generator for 5G Base Station Antenna Measurement

Plane-wave generators (PWGs) for over-the-air testing of 5G base stations offer the advantages of efficiency and economy. Many new bands, such as n28, are progressively being introduced, driving the bandwidth improvement of PWGs. The cost of amplitude–phase control networks is also increased by the broadband range required for testing. In view of the above challenges, in this paper, a low-frequency ultra-wideband PWG for testing 5G base stations is reported. Firstly, an electrically small antenna unit based on the Vivaldi antenna is design for the PWG. The antenna unit has a wide operating band and compact size, allowing it to reach a quarter of the minimum frequency wavelength. Then, the operating band from 700 MHz to 4 GHz is divided into three sub-bands, and the amplitude and phase excitations within each sub-band are optimized with multiple frequency points. Finally, the designed ultra-wideband PWG is simulated and experimentally tested. The designed 2.64 m one-dimensional linear-array PWG is able to produce a 1.5 m × 1.32 m quiet zone with less than 1.0 dB and 10°. The results of the radiation pattern measurements for the base station agree reasonably well with the MVG SG128.

Design and measurements of 6 x 6 m collimator reflector with rounded edges

Compact antenna test range (CATR) is designed to form a plane wave at a small distance from the aperture of the collimator reflector, which allows measurements to be made under far field conditions in a compact anechoic chamber. Currently, collimators are in demand due to the technical re-equipment of the industry for the production of 4G, 5G and Internet of Things stuff. The typical size of a quiet zone for these needs is 1–1.5 m. Along with antenna pattern measurements, collimators are widely used for RCS measurements. In the latter case, the measured objects may have dimensions several times larger than the average size of the quiet zone. Manufacturing, installation and adjustment of collimator reflector of several meters in size is a non-trivial task that requires separate study for each project. An incorrect choice of the reflector geometry can lead to an increase in mass and size, which entails an increase in production costs and the anechoic chamber designed for the CATR. In addition, increase in mass imposes additional requirements on the rigidity of the rack to which the reflector is attached, and the foundation under the collimator. As a rule, large-sized reflectors consist of a dozen fragments, which leads to the need to have special adjustment mechanisms for precision tuning of the reflector fragments. These and other problems need to be solved when developing large CATR. The article presents the issues faced by the LLC «RadioLine» in the process of manufacturing and setting up a collimator stand with a 6 x 6 m reflector. The issues of choosing the geometry of the reflector, its focal length have been highlighted. It has been shown how the agreement of the results of three-dimensional modeling of the reflector and production capabilities has been carried out. The features of the design of the reflector rack are touched upon, in particular, the appropriateness of using two materials: one for the base, and the second for the truss, which is connected to the reflector. After discussing the design features, a scheme for measuring the electromagnetic field distribution in a quiet zone, approaches to improving the quality of the RF characteristics of the CATR have been presented. It is noted that in the process of setting up the collimator, in order to determine the directions to the sources of diffraction, it is useful to apply the recalculation of the measured electromagnetic field in the quiet zone into the plane wave spectrum. At the end of the article, quiet zone cuts have been shown at frequencies of 0.75 GHz, 8.2 GHz and 50 GHz. Average peak-to-peak ripple of the amplitude-phase distribution in the operating frequency range of the CATR is 1 dB in amplitude and 10 degrees in phase.

CURRENT TRENDS OF SUSTAINABLE ECOLOGIZATION OF THE TOURISM INDUSTRY IN THE CHERKASY REGION

The article presents an analysis of modern trends in sustainable ecologization of the tourism industry in the Cherkasy region. Tourism is not only one of the factors of economic growth and development of recreational areas, but also an important factor in environmental problems due to irrational use of nature, negative impact on the environment, which determines the urgency of ecologization of the tourism industry at the current stage of tourism industry development. The relevance of the study is explained by insufficient coverage of the issue of ecologization of the tourism industry in the Cherkasy region in the scientific literature. All historical and cultural reserves of the region are quite far from the city of Cherkasy and are located in a picturesque area rich in natural recreational resources, which leads to the active development of tourism there, but this does not always have a positive effect on the environment. The study reveals the prospects for reducing and avoiding the negative consequences of tourism for the environment in the long run with the help of better coordination and preventive planning, environmentally friendly transport concepts, the use of environmentally compatible supply and disposal technologies and careful management of the tourism organizations activities. The article proves that today in Ukraine there is a quite acute problem of determining the needs for the sustainable development of various types of tourism depending on the availability of natural, anthropogenic and natural-anthropogenic tourism resources in various regions of the country, and in the Cherkasy region in particular, as well as the preservation of these resources, since the impact of tourism on the environment is global and irrational use of resources can lead to irreversible consequences. It is expedient to build a strategy for the development of ecological tourism with the help of the relevant authorities of nature conservation areas and the state tourism administration and with the support of national and regional administrations. The concept of sustainable development of tourism should be aimed at promoting the development of settlements and at the same time protecting natural resources. One of the means of preserving the environment can be the allocation of quiet zones according to ecological aspects, in which tourist buildings should be avoided, and pristine natural areas and landscapes preserved.

A novel metasurface lens antenna design for over‐the‐air testing in millimetre wave radio resource management measurement

AbstractIn millimetre wave (mmWave) frequency band, radio resource management (RRM) performance is characterised in plane wave conditions using radiated over‐the‐air test method, which is a challenging combination of protocol and radio frequency performance measurement. This article presents a novel design of multiple lens‐based compact antenna test ranges (CATRs) to simulate multiple angles of arrival from different base‐stations in RRM measurement. Only four lens‐based CATRs are proposed to create plane wave conditions at the device under test with six different angles of arrival and capable of accurately constructing the wireless propagation condition and minimising the diffraction and scattering between adjacent CATRs. The lens‐based CATR is the key element in the RRM measurement system, which is composed of a metasurface lens for phase alignment and a 2 × 2 feed array antenna for the emission of electromagnetic signals. The function and capability of the proposed lens‐based CATR is validated through simulation and measurement, that the worst‐case amplitude variation in the quiet zone region is lower than ±0.8 dB at 26 GHz, and phase variation is lower than ±7.5° in the designed quiet zone, which could be used in the fifth‐generation mmWave RRM measurement.

Crustal Structure of the Jurassic Quiet Zone in the West Pacific Ocean: Insights from 2D Multichannel Seismic Reflection Profiles

Crustal Structure of the Jurassic Quiet Zone in the West Pacific Ocean: Insights from 2D Multichannel Seismic Reflection Profiles

Acoustic compact test range system for large-scale target characteristic testing in a shorter distance

In the acoustic scattering and characteristic tests of large targets and large-scale transducers, in order to meet the plane wave conditions, the larger test distance is often required. It is a greater difficulty for the testing laboratories with limited space. In order to compact the testing distance and solve the problem of requiring a long distance for large-scale target scattering and large-scale transducer testing, based on the principle and application of microwave compact test rang system and the approximation of electromagnetic wave and acoustic wave, an underwater acoustic compact range test system (ACTRS) is proposed. The developed ACTRS uses a parabolic main reflector to obtain a plane wave at a short distance. Compared to the traditional underwater acoustic test system, the space distance is effectively compacted and the conversion process is reduced. Moreover, as the main device in the proposed ACTRS, the air-cavity with resin honeycomb structure was selected as the basic unit cell of the main reflector for the good underwater acoustic reflection performance. In addition, the edge sawtooth structure was selected to reduce the interference of edge diffraction in the quiet zone. Subsequently, the main reflector was simulated, trial-produced and measured. The measurement result shows good agreement with the simulation result. Finally, based on the proposed main reflector, the ACRTS was constructed for the object scattering and transducer directivity measurements. The test results were consistent with the simulation and the manufacturer’s manual data. Overall, the designed ACTRS can be used for large-scale target scattering and transducer directivity testing, providing a new reference for exploration of acoustic measurement methods.

Effective Sparse Recovery Framework for Ultrawideband Robust Plane Wave Generator

This letter proposes a novel ultrawideband plane wave generator (PWG) design methodology suitable for a low-cost small anechoic chamber. Several novel strategies are proposed to handle various crucial concerns in practice to make the proposed methodology reliable and robust. Specifically, the subarray-based amplitude-only excitation method is capable of reducing the required number of control channels without the need for phase shifters, which can significantly simplify the feeding network complexity. One major concern of the PWG application is the nonnegligible multipath reflections in small anechoic chambers. Thus, a novel regression approach, imposing the constraint of maximum energy outside the quiet zone (QZ), is implemented to suppress the reflection level. For the design of the PWG layout, a compressed sensing-based adaptive backtracking orthogonal matching pursuit (ABOMP) algorithm is proposed. In the simulation, a spherical test zone supporting the ultrawideband frequency over 2.4–5 GHz is synthesized with the proposed methodology, and the effectiveness and robustness are comprehensively investigated.

Theoretical Verification of Single-Reflector Compact Antenna Test Range With High Aperture Usage

In the reflector-based compact antenna test range (CATR), the aperture usage is one of our most concerned problems. Higher aperture usage means that in a CATR with the same aperture reflector, a larger quiet zone (QZ) can be generated to measure a larger aperture antenna. In this work, we theoretically derive a method to design a single-reflector CATR with high aperture usage. Specifically, the radiation function of the ideal feed for the offset-fed CATR is deduced. An offset-fed parabolic reflector CATR with this ideal feed can generate a QZ with 100% aperture usage analyzed by geometrical optics (GO). An offset-fed CATR with a 3 m side-length rectangular aperture parabolic reflector is designed and simulated by physical optics (PO) and physical theory of diffraction (PTD) in GRASP10. With the proposed feed, the aperture efficiency can reach about 74% at 100 GHz and over 86% from 200 to 500 GHz. The simulation results of the QZ field distribution in the system with an ideal feed and a manufactured coaxial cavity horn feed are presented and analyzed. Besides, we also summarize amplitude ripple, phase ripple, and cross-polarization isolation in the QZ to illustrate the performance of the single-reflector CATR.

Recent Technological Advances in Spatial Active Noise Control Systems

This article provides a broad overview of the recent advances in the field of active noise control techniques to reduce unwanted noise over a certain spatial region of interest. By both commercial and technological advances in local active noise control systems extending the size of the quiet zone seems to be a crucial step to develop the next generation of active control systems for a more personalized and quieter audio products. In this review article, the advances over the past decade in design and development of spatial active noise control techniques to enlarge the controlled sound zone is reviewed. The focus is specifically on the adaptive control techniques and the methods proposed in the frequency domain to control the sound field. The study has paid a specific attention into the most important performance measures in designing a spatial active noise control system such as convergence rate, stability and robustness of the algorithm, and the size of quite zone and how it can be enlarged by configuring the loudspeaker and microphone array geometries. Finally, the authors will discuss the current and future challenges that should be overcome to improve the effectiveness of the recently proposed methods to expand the silence zone.

Remote Microphone Technique for Active Noise Control Over Distributed Networks

Multichannel Active Noise Control (ANC) headrest systems have usually been designed with the objective of creating quiet areas at the passenger positions within the cabin of a public transport. Due to the high computational demands of dealing with multiple loudspeakers and multiple microphones by using a single centralized processor, and the convenience of a scalable system, a distributed implementation may be advisable. On the other hand, the addition of the remote microphone (RM) technique to the ANC headrest systems has recently allowed the creation of local zones of quiet at unachievable placements for the error sensors. This technique allows the quiet zone to be shifted to a desired location away from the physical sensor. However, to our knowledge, the implementation of an ANC headrest system with virtual microphones over a distributed acoustic sensor network has not been addressed. In this work, a distributed version of the multiple-error FxLMS (MEFxLMS) algorithm considering the RM method (RM-DMEFxLMS) is proposed by using an alternative formulation of the RM method. Through a set of simulations, it is found that on a non-constrained communication network, the proposed algorithm presents the same performance of its centralized version and provides a scalable and more versatile ANC system.

Synthesis of Plane-Wave Generator in 3-D Sphere Quiet Zone for Advanced Antenna Measurement by Hybridizing LSM and GA

Synthesis of Plane-Wave Generator in 3-D Sphere Quiet Zone for Advanced Antenna Measurement by Hybridizing LSM and GA

Дисфункція дрібних дихальних шляхів та можливості її корекції при астмі

Abstract. Background. Although randomized controlled trials have shown that asthma control is an achievable goal, real-life studies over the past 20 years have shown that asthma remains poorly controlled in a significant proportion of patients, even among those receiving treatment at asthma specialist, and in patients with mild asthma who regularly take inhaled corticosteroids. Even when asthma control is achieved, it is not optimal on all GINA steps. The small airways have been recognized as the primary site of airflow limitation in asthma. The aim of the work: to study, according to the literature, the peculiarities of the dysfunction of the small airways in asthma and to evaluate the possibilities of its treatment. Materials and methods. Scientific articles that covered the pathophysiology of small airways disorders, their impact on asthma control, diagnostic methods, and pharmacological treatment methods were analyzed. The results. Airways with an internal diameter < 2 mm, which do not contain cartilage in their walls and extend from the 8th generation of the airways to the periphery of the lung, are collectively called “small airways”. They are called the QUIET ZONE because they are difficult to assess and treat in patients with asthma who are not optimally controlled but have relatively normal FEV1 and disproportionate small airways dysfunction (SAD). Predominant in patients at all stages of treatment, associated with poor disease control. The ATLANTIS study showed that up to 91 % of patients with asthma have. The small airways have a high density of corticosteroid and β2-adrenoceptors, which means that they can be influenced. The main task is that the drugs should reach these small airways. Conventional inhalers that generate particles larger than 2 μm do not address the problem of SAD in patients with asthma. Inhaler devices that produce ultrafine particles of inhaled corticosteroids alone or in combination with long-acting β-agonists with a diameter of less than 2 μm have the potential to improve long-term asthma control along with a corresponding improvement in small airway function. The fixed combination of beclomethasone dipropionate with formoterol has optimal deposition in the respiratory tract — central pulmonary deposition accounts for 66 %, and peripheral — 34 % of the dose, thus the drug is delivered to both the central and peripheral respiratory tracts and affects inflammation and bronchoconstriction throughout the lungs. This is facilitated by MODULITE technology. The effectiveness and safety of the use of the BDP/F combination (Foster) in MART regimen is confirmed by a significant evidence base, which guaranteed its place in the Track1 treatment of asthma. Conclusions: Patients with asthma have a serious inflammatory process in the peripheral airways, which makes them the main site of obstruction in asthma; SAD predominates in patients at all stages of asthma, is associated with poor disease control, is responsible for air trapping, correlates with poor asthma control1, and predicts an increased risk of exacerbations in patients. The fixed combination of beclamethasone/formoterol in one inhaler (Foster) is the only extrafinely dispersed fixed combination of ICS/LABA that reaches the small airways; the fixed combination of BDP/Formoterol in the MART regimen provides a significant reduction in the frequency of severe complications, hospitalizations, emergency calls, and reduces the number of courses of systemic corticosteroids.