Papers by Keyword: Acoustics

Abstract: Efficient cleaning of contaminations in the semiconductor industry is a determining factor in ensuring the good quality of the electronics products. We present here the dynamic wetting characterization of a fluid on top of DTI structures using ultra-high frequency acoustic method. The dynamics of the fluid will be established using a PDMS micro-channel placed on top of the structures, in order to obtain conditions as close as possible to those used in the industrial process. Wetting state of the DTI structures is determined based on the measured acoustic reflection coefficient.

Abstract: A surface charge density distribution on natural crystal samples is investigated in the paper. Here are revealed regularities of electromagnetic signal amplitude changes upon acoustic excitation of electrified calcite samples depending on the size of the crystals.

Abstract: The problem of an assessment of the monitoring of lining condition in the Blast Furnace hearth during its campaign today has no unambiguous solution. Various techniques for the diagnostics have their own merits and demerits [1]. In this paper, characteristics of the diagnostic methods based on the measurements of temperatures in the lining, heat transfer of the cooling system and acoustic effects are considered. Various techniques can be combined and formulated into a uniform package of the strongest measures.

Abstract: Implementation of double transparent facades (DTF) into architectural concept of modern intelligent buildings is a well established trend of modern administrative building design. The Positive influence on acoustic comfort of a working place caused by this type of envelope construction is evident. DTF allow building designing in high noise exposure urban areas. Comparison of eight DTF from structural and acoustic properties point of view is presented in this paper. Results from acoustic measurements of buildings situated in Bratislava were analyzed.

Abstract: The contribution presents a mathematical modification of Watters’ formula used in modified Watters’ method. This formula expresses a dependence of sound reduction index on surface mass (mass law). On the basis of the previous research which resulted in the finding that the Watters’ method do not give acceptable results for simple walls from aerated concrete, the mentioned formula was modified to be usable for theoretical determination of sound reduction index of simple aerated concrete walls. The contribution also presents a modification of this formula for calculation of sound reduction index of simple aerated concrete walls with a plaster on both sides.

Abstract: The calculation of the structural intensity allows for a better understanding of the NVH behavior of complex structures as it shows vibratory energy flows between an excitation and radiating areas. However, the information gathered is underlying aleatory and epistemic uncertainties and needs to be dealt with carefully. In this paper two aspects are discussed: Firstly how the structural intensity calculation helps to reduce uncertainty in NVH design and secondly what currently existing uncertainties need to be considered and how they can be further reduced. This does not only include an improvement of the current calculation process itself but also an extension towards an integrated, holistic calculation of vibratory energetic quantities for structure-borne and air-borne sound.

Abstract: Many of the machines and systems having rotating components are designed for operation at high speeds, and hence, it is obvious that only these elements are damaged initially and becomes the root cause of a defect in any machine. Using on line, continuous monitoring techniques, any defect in a rotating part can be detected at its initial stage itself and the user could be alerted before it leads to a catastrophic failure. In this experimental work of the acoustical failure diagnosis, three domestic mixers, the first one in healthy condition, the next mixer about to fail and the last with completely damaged bush were analyzed, with a Type-1 and Delta ohm HD2010 Model sound level meter (SLM). The acoustical readings of the three mixers were measured and tabulated in decibel, using Delta Ohm Noise Studio software. Graphs were drawn for different sets of readings and by analyzing the graphs of the three mixers, the threshold value of the initiation of the defect was found to be 80 decibel, at which failure starts.

Abstract: The present work describes an investigation into a vibro-acoustic method to check the existence of superficial flaws in composite sandwich structures, based in a technique inspired in the well known Tap Test. In this case, however, a non-impulsive excitation is provided by an especial transducer and the acoustic response is captured with a microphone. A deconvolution technique is used in order to assess the system's impulse response and generate a “failure” map after post-processing the results. Post-processed parameters evaluated are: Loudness, Sharpness and a discrepancy indicator for the transfer function (named TFDI). Results suggest that Loudness and TFDI potentially indicate the existence of a damaged core and the lack of adhesive tape.

Abstract: The natural wealth of Indonesia produces a wide range of natural resources. This research will discuss sawdust and coconut fiber for example from natural resources which can be processed into building materials. Various researches have studied the absorber made from sawdust and coconut fiber, but only a few studies that made the absorber material that had the texture of waffle on its surface. The research method used was the method comparisons of density, absorption coefficient and Sound Transmission Loss (STL). The result is that the waffle panel from sawdust has a higher density than the waffle panel made of coconut fiber. The STL of the coconut fiber panel has ranged between 46,134 – 51,312 dB. This value is lower than the STL material of sawdust that has a value between 47,301 – 62,688 STL. The absorption coefficient of coconut fiber panels is 0,432–0,511, while the absorption coefficient of sawdust panel has range of 0,469 – 0,529.

Abstract: The paper deals with the application of the so-called T-type finite elements [1] to the calculation of the exterior acoustic problems in two dimensions. The method is based on the use of asuitably truncated T-complete set of Trefftz functions over individual subdomains linked by means ofa least square procedure. The vertex singularities and the Sommerfeld radiation condition are readilyincorporated in the trial functions. In order to show the performance of the approach two examples ofcomputations for infinite cylinders (of circular and square cross section) are presented and comparedwith those obtained by means of h-adaptive FE method [2].