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NUMERICAL TRANSFER PATH ANALYSIS FOR STRUCTURE-BORNE AND AIR-BORNE NOISE PROBLEMS IN INTERNAL COMBUSTION ENGINES
No full textOperational transfer path analysis of a piano
No full textThe piano sound is made audible by the vibration of its soundboard. A pianist pushes the key to release a hammer that strikes the strings, which transfer the energy to the soundboard, set it into vibration and the piano sound is heard due to the compression of air surrounding the soundboard. However, as piano is being played, other components such as the rims, cast-iron frame and the lid are also vibrating. This raises a question of how much of their vibrations are contributing to the sound as compared to the soundboard. To answer this question, operational transfer path analysis, a noise source identification technique used widely in automotive acoustics, is carried out on a Bösendorfer 280VC-9 grand piano. The “noise” in a piano system would be the piano sound while the “sources” are soundboard and the aforementioned components. For this particular piano, it is found out that the soundboard is the dominant contributor. However, at high frequencies, the lid contributes the most to the piano sound.</p
Surface noise contributions analysis in wave based method framework for exterior radiation noise problems
No full textSubstructuring of multibody systems for numerical transfer path analysis in internal combustion engines
No full textAPPLICATION OF A NUMERICAL TRANSFER PATH ANALYSIS METHOD FOR NOISE SOURCE IDENTIFICATION IN INTERNAL COMBUSTION ENGINES
No full textNumerical transfer path analysis for the assessment of air-borne noise in internal combustion engines
No full textInfluences of system uncertainties on the numerical transfer path analysis of engine systems
No full textPractical mechanical systems operate with some degree of uncertainty. In numerical models uncertainties can result from poorly known or variable parameters, from geometrical approximation, from discretization or numerical errors, from uncertain inputs or from rapidly changing forcing that can be best described in a stochastic framework. Recently, random matrix theory was introduced to take parameter uncertainties into account in numerical modeling problems. In particular in this paper, Wishart random matrix theory is applied on a multi-body dynamic system to generate random variations of the properties of system components. Multi-body dynamics is a powerful numerical tool largely implemented during the design of new engines. In this paper the influence of model parameter variability on the results obtained from the multi-body simulation of engine dynamics is investigated. The aim is to define a methodology to properly assess and rank system sources when dealing with uncertainties. Particular attention is paid to the influence of these uncertainties on the analysis and the assessment of the different engine vibration sources. Examples of the effects of different levels of uncertainties are illustrated by means of examples using a representative numerical powertrain model. A numerical transfer path analysis, based on system dynamic substructuring, is used to derive and assess the internal engine vibration sources. The results obtained from this analysis are used to derive correlations between parameter uncertainties and statistical distribution of results. The derived statistical information can be used to advance the knowledge of the multi-body analysis and the assessment of system sources when uncertainties in model parameters are considered
Contribution of the vibration of various piano components in the resulting piano sound
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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