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Influence of Double-Panel Structure Modification on Vibroacoustical Properties of a Rigid Device Casing

Chrapońska Anna, Rzepecki Jarosław, Mazur Krzysztof, Wrona Stanisław, Pawełczyk Marek

Archives of Acoustics

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2020

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Vol. 45, No. 1

119--127

EN

Nowadays, noise generated by devices is a serious issue in industry and in everyday life, because it may cause health damage to humans. In this research, a cubic rigid device casing built of double-panel thin steel walls is employed to reduce noise emitted from an enclosed noise source. Double-panel structure is used because of good sound insulation it provides. There exist three main groups of noise reduction methods, i.e. passive, semi-active and active. In this paper, a semi-active modification of double-panel structure is applied and examined. The bistable actuator (solenoid) mounted between incident and radiating plates changes its state due to applied constant voltage, causing the coupling of plates. Experimentally measured natural frequencies and modeshapes of the structure are compared to the simulation results. The influence of proposed modification on dynamical properties of the structure is analyzed and discussed.

2

Analiza wpływu technologii oraz metod przesyłania hologramu na parametry i efekty transmisji

Mazur Krzysztof, Mazur Damian

Journal of Computer Sciences Institute

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2019

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Vol. 12

220--225

PL

Celem artykułu jest porównanie i analiza wpływu technologii i technik przesyłania danych, pod kątem wyświetlania obrazu przy pomocy ostrosłupa holograficznego. Oceniając użyteczność rozwiązania pod uwagę będą brane parametry: czas przesyłania klatek obrazu, użycie parametrów fizycznych maszyny i parametry pracy Wirtualnej Maszyny Javy.

EN

The aim of the article is to compare and analyze the impact of technologies and data transfer techniques in term of displaying the image using a holographic pyramid. When assessing the usability of the solution, the following parameters will be taken into account: time of image transfer, use of physical parameters of the machine and parameters of the Java Virtual Machine.

3

Sound Transmission Through a Thin Plate with Shaped Frequency Response

Wrona Stanislaw, Mazur Krzysztof, Rzepecki Jaroslaw, Chraponska Anna, Pawelczyk Marek

Archives of Acoustics

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2019

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Vol. 44, No. 4

731--738

EN

Thin plates, in the form of individual panels or whole device casings, often separate the noise source from its recipients. It would be very desirable if the panels could effectively block the sound transmission preventing noise from further propagation. This is especially challenging to achieve at low frequencies. A promising approach, intensively developed in the recent years, is to employ active control methods by adding sensors and actuators, and running a control algorithm. However, if the noise is narrow-band, an alternative passive solution originally developed by the authors can be applied. It is based on appropriately located passive elements which can be used to alter the frequency response of the vibrating structure thus improving its sound insulation properties. Such an approach is referred to as the frequency response shaping method. The purpose of this paper is to further develop this method and apply it to a device casing panel. The efficiency of the method is evaluated by simulation and real experiments. Appropriate cost functions and mathematical models are formulated and used to optimise the arrangement of passive elements mounted to the plate, enhancing its sound insulation properties at the given frequency range. The results are reported, and advantages and limits of the method are pointed out and discussed.

4

FXLMS with Multiple Error Switching for Active Noise-Cancelling Casings

Mazur Krzysztof, Wrona Stanislaw, Chraponska Anna, Rzepecki Jaroslaw, Pawelczyk Marek

Archives of Acoustics

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2019

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Vol. 44, No. 4

775--782

EN

Passive noise reduction methods require thick and heavy barriers to be effective for low frequencies and those clasical ones are thus not suitable for reduction of low frequency noise generated by devices. Active noise-cancelling casings, where casing walls vibrations are actively controlled, are an interesting alternative that can provide much higher low-frequency noise reduction. Such systems, compared to classical ANC systems, can provide not only local, but also global noise reduction, which is highly expected for most applications. For effective control of casing vibrations a large number of actuators is required. Additionally, a high number of error sensors, usually microphones that measure noise emission from the device, is also required. All actuators have an effect on all error sensors, and the control system must take into account all paths, from each actuator to each error sensor. The Multiple Error FXLMS has very high computational requirements. To reduce it a Switched-Error FXLMS, where only one error signal is used at the given time, have been proposed. This, however, significantly reduces convergence rate. In this paper an algorithm that uses multiple errors at once, but not all, is proposed. The performance of various algorithm variants is compared using simulations with the models obtained from real active-noise cancelling casing.