Detection of a predefined acoustic pattern by a measurement system on a drone and its application to search for a missing man in an underground mine

Due to the very difficult working conditions and a certain number of hazards that do not occur in other industries, the operation of rescue units in underground mines is necessary. The area of exploitation is usually very large, thus determining the location of a person, which may be in need due to the accident, is not an easy task. As the time for reaching such a person is crucial, there is a strong need for a solution that would provide a quick establishment of the victims’ location. Moreover, conducting a rescue mission is always associated with risk exposure for rescuers’ life and health. Thus, in this paper, we propose a solution based on an unmanned aerial vehicle (UAV) for a predefined acoustic pattern detection to support rescue units in human location assessment in the underground mine. The presented method is based on measuring the dissimilarity between the subsequent short-time power spectra and the referential spectrum characterizing the UAV’s ego-noise. This relatively general and data-driven approach is applied both to generated narrowband harmonic patterns and to the human voice. As the analyzed signals of interest are of specific frequency content they can be selected from the background noise with the use of band-pass filtering.

On the relation between the similarity of the acoustic distribution patterns of vowels and the language closeness

Based on the “Unified Platform for Speech Acoustic Parameters of Chinese Minority Languages”, this paper calculates and compares the acoustic distribution of vowels in Mongolian, Uyghur, and Ewenki and proposes a hypothesis that the relevance between the similarity of the acoustic distribution patterns of vowels and language closeness does exist. It indicates that the acoustic pattern implies clues of closeness and relevance among the three languages. The results demonstrate that, in terms of vowels, Mongolian and Ewenki are closely related. Both those languages and the Uyghur language are distant relatives, with only typological similarity. This paper provides a new perspective for the research methodology of language kindred. It proves that the comparison of acoustic pattern is of significance in studies in linguistics, linguistic typology, historical comparative linguistics, and anthropology.

FLOWSTANDART PHONOPNEUMOGRAPHY QUIET BREATHING IN THE DIAGNOSIS OF COMORBID CURRENT COMMUNITYACQUIRED PNEUMONIA

The aim of our study was to estimate the potential of the flow about standardized panoramogram quiet breathing (PFPG SD) for the diagnosis of inflammation in patients with community-acquired pneumonia on a background of chronic obstructive pulmonary disease (COPD).Materials and methods: 36 healthy male volunteers aged 18 to 76 years old and 36 men with CAP on the background of COPD aged 45 to 80 years old, hospitalized in the Department of the Ministry of Defense of the Far East Branch of the Russian Academy of Sciences, and were examined. PFPG SD was performed on admission to all patients and healthy individuals.Results and discussion: Spectral criteria for acoustic diagnostics of the focus of patients with CAP on the background of COPD were developed, determined by PFPG SD. The maximum specificity for the group of healthy people was reached — 80,5%, the maximum sensitivity of detecting the focus of inflammation — 83,3%. The sensitivity of PFPG SD exceeds the sensitivity of subjective auscultation. The types of acoustic pattern and their threshold values for patients were revealed.

Feasibility analysis for active near/far field acoustic pattern synthesis in free space and shallow water environments

In this paper, a detailed sensitivity and feasibility analysis of the active manipulation scheme for scalar Helmholtz fields proposed in our previous works, in both free space and constant-depth homogeneous ocean environments, is presented. We apply the method of moments (MoM) together with Tikhonov regularization with the Morozov discrepancy principle to investigate the effects of varying the problem parameters to the accuracy and feasibility of the proposed active field control strategy. We discuss the feasibility of the active scheme (with respect to power budget, control accuracy and process error) as a function of the frequency, the distance between the control region and the source, the mutual distance between the control regions, and the size of the control region. Process error is considered as well to investigate the possibility of an accurate active control in the presence of manufacturing or feeding noise. The numerical simulations show the accuracy of the active field control scheme and indicate some challenges and limitations for its physical implementation.

Prediction of Squeal Noise Based on Multiresolution Signal Decomposition and Wavelet Representation—Application to FEM Brake Systems Subjected to Friction-Induced Vibration

This paper is devoted to discussion of the efficiency of reduced models based on a Double Modal Synthesis method that combines a classical modal reduction and a condensation at the frictional interfaces by computing a reduced complex mode basis, for the prediction of squeal noise of mechanical systems subjected to friction-induced vibration. More specifically, the use of the multiresolution signal decomposition of acoustic radiation and wavelet representation will be proposed to analyze details of a pattern on different observation scales ranging from the pixel to the size of the complete acoustic pattern. Based on this approach and the definition of specific resulting criteria, it is possible to quantify the differences in the representation of the acoustic fields for different reduced models and thus to perform convergence studies for different scales of representation in order to evaluate the potential of reduced models. The effectiveness of the proposed approach is tested on the finite element model of a simplified brake system that is composed of a disc and two pads. The contact is modeled by introducing contact elements at the two friction interfaces with the classical Coulomb law and a constant friction coefficient. It is demonstrated that the new proposed criteria, based on multiresolution signal decomposition, allow us to provide satisfactory results for the choice of an efficient reduced model for predicting acoustic radiation due to squeal noise.

Numerical Characterisation of the Aeroacoustic Signature of Propeller Arrays for Distributed Electric Propulsion

This paper presents an investigation of the aerodynamic and aeroacoustic interaction of propellers for distributed electric propulsion applications. The rationale underlying the research is related to the key role that aeroacoustics plays in the establishment of the future commercial aviation scenario. The sustainable development of airborne transportation system is currently constrained by community noise, which limits the operations of existing airports and prevents the building of new ones. In addition, the substantial saturation of the existing noise abatement technologies inhibits the further development of the existing fleet, and imposes the adoption of disruptive configurations in terms of airframe layout and propulsion technology. Simulation-based data may help in clarifying many aspects related to the acoustic impact of such innovative concepts. Blended-wing-body equipped with distributed electric propulsion is one of the most promising, due to the beneficial effect of the substantial shielding induced by its geometry. Nevertheless, the novelty of the layout requires a thorough investigation of specific aspect for which no previous experience is available. Herein, the interaction between propellers is analysed for a fixed propeller geometry, as a function of their mutual distance and compared to the acoustic pattern of the isolated one. The aerodynamic results have been obtained using a boundary integral formulation for unsteady, incompressible, potential flows which accounts for the interaction between free wakes and propellers. For the aeroacoustic analyses, the Farassat 1A boundary integral formulation for the solution of the Ffowcs Williams and Hawkings equation has been used. These results provide an insight into the minimum distance between propellers to avoid aerodynamic/aeroacoustic interaction effects, which is an important starting point for the development of distributed propulsion systems.