CLASSIFICATION AND MODELLING OF SOUND EMISSION SIGNALS IN SELECTED TRIBOSYSTEMS

The paper presents an analysis of the sound level recorded during dry sliding friction conditions. Balls with a diameter of 6 mm placed on pins were made of 100Cr6 steel, silicon carbide (SiC), and corundum (Al2O3), while rotating discs with a height of 6 mm and a diameter of 42 mm were made of 100Cr6 steel. Each pin and disc system was tested for two values of the relative humidity of the air (50 ± 5% and 90 ± 5%). Models of the A-sound level were developed using regression trees and random forest. The paper presents an analysis of the accuracy of the models obtained. Classifications of the six tests performed on the basis of sound level descriptors were also carried out.

Sound emission of solid surfaces through bubble layer

The analysis of the influence of a thin homogeneous bubble layer on sound emission from a solid surface is carried out. Sound pulses and monochromatic wave packets with a carrier frequency equal to the resonant frequency of the bubbles forming the bubble layer are considered. It is shown that the bubble layer transforms short sound pulses into wave sound packets and significantly reduces the amplitude of the emitted sound. The structure of a sinusoidal wave packet is transformed similarly. A long sound pulse is stored in the form of a pulse, its shape changes significantly. A homogeneous bubble layer near a solid radiating surface is an open resonator. The layer generates far-field radiation with spectral lines depending on the method of layer excitation and the internal properties of the bubble layer. The resonant frequency of the bubble is the limiting frequency in the spectrum, but it is not distinguished by a separate line.

An investigation on cutting sound effect on power consumption and surface roughness in CBN tool-assisted hard turning

In machining activities, sound emission is one of the key factors toward the operator's health and safety. Sound generation during cutting is the outcome of the interaction between tool and work. The intensity of sound greatly influences the cutting power consumption and surface finish obtained during machining. Therefore, the current work emphasized the analysis of sound emission, power consumption, and surface roughness in hard turning of AISI 4340 steel using a CBN tool which was rarely found in the literature. Response surface methodology (RSM) and artificial neural network (ANN) techniques were utilized to formulate the model for each response. The results indicated that the maximum value of input parameters exhibited the highest level of sound due to the creation of vibration in the machine and tool. Higher sound level indicates the generation of lower power consumption but at the same instant surface roughness was leading with increment in sound level. The feed rate exhibited the utmost noteworthy consequence on surface quality with 87.71% contribution. The cutting power can be decreased by choosing the high level of cutting parameters. The RSM and ANN have a good correlation with experimental data, but the accuracy of the ANN is better than the RSM.

Influence of vehicle source directivity in Japanese and European outdoor sound prediction models under a semi-finite thick barrier configuration

The Japanese ASJ RTN-Model 2018, European Harmonoise and CNOSSOS-EU outdoor sound prediction models are respectively known to have symmetric, asymmetric and omnidirectional sound emission directivities along front-back direction of the source vehicle. However, the influence of such difference in directivities to final predicted sound levels has not been investigated much. In this study, the influence is investigated using the ASJ Model and the Harmonoise under a configuration of semi-finite thick barrier along a source road. The configuration is an idealization of Japanese roadside buildings that have gaps in between, unlike European buildings that continuously extend over a whole urban block. Under the configuration, distribution of A-weighted sound levels around the end face of the barrier are computed with and without source directivity taken into account by each model. It is found from the results that the source directivity of the ASJ model makes little difference in the noise level distribution. In contrast, the source directivity of Harmonoise is found to make differences of 0.5-0.8 dB at right behind the barrier depending on vehicle running direction. However, a combined effect of source directivity and reflection at the end face is found to be negligible.

Experimental study of particle dampers applied to wind turbine blades to reduce low-frequency sound emission

Sound emission from an onshore wind turbine is one of the significant hurdles to use wind energy to its full potential. The vibration caused by the generator is transmitted to the blades, which radiates the sound to the surrounding. The purpose of this experimental study is to present a passive vibration reduction concept, which is based on the high damping properties of granular materials. The efficiency of this concept will be investigated using a laser scanning vibrometer device. For the experimental purpose in the laboratory, small-scale replicas inspired by the original configurations are used as reference geometries for the wind turbine generator and the blades. Vibrations of the prototype, with and without granular material filling, will be determined and compared with each other. The influence of the amount of granular material inside the structure is also investigated. Apart from this, different types of granular filling are examined with respect to their efficiency in reducing the amplitude of vibration of the structure while being as light as possible in order to design a lightweight solution, which increases the overall mass of the wind turbine marginally.

CNN-based multi-class multi-label classification of sound scenes in the context of wind turbine sound emission measurements

Within the scope of the interdisciplinary project WEA-Akzeptanz, measurements of the sound emission of wind turbines were carried out at the Leibniz University Hannover. Due to the environment there are interfering components (e. g. traffic, birdsong, wind, rain, ...) in the recorded signals. Depending on the subsequent signal processing and analysis, it may be necessary to identify sections with the raw sound of a wind turbine, recordings with the purest possible background noise or even a specific combination of interfering noises. Due to the amount of data, a manual classification of the audio signals is usually not feasible and an automated classification becomes necessary. In this paper, we extend our previously proposed multi-class single-label classification model to a multi-class multi-label model, which reflects the real-world acoustic conditions around wind turbines more accurately and allows for finer-grained evaluations. We first provide a short overview of the data acquisition and the dataset. We then briefly summarize our previous approach, extend it to a multi-class multi-label formulation, and analyze the trained convolutional neural network regarding different metrics. All in all, the model delivers very reliable classification results with an overall example-based F1-score of about 80 % for a multi-label classification of 12 classes.

Estado da arte no monitoramento acústico de Cicadidae em lavouras de café

As cigarras são uma praga-chave das lavouras de café com a característica marcante de emissão de sons. É de interesse do produtor o desenvolvimento de ferramentas para monitoramento das lavouras, buscando economia de recursos. Este trabalho realiza um levantamento bibliográfico dos trabalhos focados no monitoramento acústico de Cicadidae procurando soluções disponíveis para auxílio do produtor. Os resultados mostraram que a maioria dos trabalhos encontrados (52,3%) utiliza softwares em laboratório e apenas 4,7% utiliza algum software para monitoramento implantado em campo. Conclui-se, a partir desse dado, que essa pode ser uma importante lacuna a ser preenchida em trabalhos futuros, por meio do processamento digital de sinais de áudio em um possível dispositivo implantado em lavoura. Abstract: Cicadas are a key pest of coffee plantations with a marked sound emission characteristic. It is of interest to the producer to develop tools to monitor crops in order to save resources. This research performs a bibliographic survey of works focused on the acoustic monitoring of Cicadidae, in order to look for available solutions to help producers. The results showed that the majority of the works founded (52.3%) are related to the use of softwares in laboratory, and only 4.7% use some monitoring software implemented in the field. Therefore, that must be an important gap to be filled in future works, applying digital audio signal processing in a possible device implanted in a field. Keywords: Bioacoustics, Digital Audio Signal Processing, Monitoring.

Trailing Harry Potter into Romanian

Characteristic of English and other Germanic languages, Goal of Motion constructions represent a challenge for any translator rendering them into a Romance language. This is because to express the motion of an entity to/towards a Goal in a particular manner, English typically combines a manner-of-motion verb or a verb of sound emission with a dynamic preposition like into in He ran into the park. However, the combination is not generally available in Romanian and other Romance languages, since they not only lack dynamic prepositions, but also have far fewer manner-of-motion verbs. Consequently, to render Goal of Motion into Romanian with as little loss as possible, a translator will have to resort to various translation techniques to compensate not only for the lack of dynamic prepositions in this language, but also for its far poorer class of manner-of-motion verbs. This paper proposes several strategies for the translation of Goal of Motion constructions into Romanian and shows that they depend on the lexical and syntactic resources available in this language. An analysis of the techniques employed in a selected sample from two Romanian translations of the Harry Potter series indicates that the translators' strategies generally mirror Talmy's (1985, 2000) typological classification of Germanic and Romance languages into satellite-framed and verb-framed languages, respectively.