Wyniki wyszukiwania - Biblioteka Nauki

1

Sound Intensity Distribution Around Organ Pipe

100%

Odya P. , Kotus J. , Szczodrak M. , Kostek B.

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tom Vol. 42, No. 1

13--22

EN

The aim of the paper was to compare acoustic field around the open and stopped organ pipes. The wooden organ pipe was located in the anechoic chamber and activated with a constant air flow, produced by an external air-compressor. Thus, a long-term steady state response was possible to obtain. Multichannel acoustic vector sensor was used to measure the sound intensity distribution of radiated acoustic energy. Measurements have been carried out on a defined fixed grid of points. A specialized Cartesian robot allowed for a precise positioning of the acoustic probe. The resulted data were processed in order to obtain and visualize the sound intensity distribution around the pipe, taking into account the type of the organ pipe, frequency of the generated sound, the sound pressure level and the direction of acoustic energy propagation. For the open pipe, an additional sound source was identified at the top of the pipe. In this case, the streamlines in front of the pipe are propagated horizontally and in a greater distance than in a case of the stopped pipe, moreover they are directed downwards. For the stopped pipe, the streamlines of the acoustic flow were directed upwards. The results for both pipe types were compared and discussed in the paper.

2

The Use of Acoustic Vectors Decomposition of Sound Fields to Vibroacoustic Protection on Ships

100%

Weyna S.

Archives of Acoustics

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2017

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tom Vol. 42, No. 2

207--212

EN

In this paper, numerous examples will be illustrated as principles of applying the sound intensity measurements to practical problems at the noise abatement on ships and offshore constructions. The paper presents the results of transmission loss measurements together with flanking transmission for ship bulkheads and partitions with doors and windows. Investigations carried out with sound intensity measurement techniques will be compared against those made by classical methods. Finally for a few examples, the graphic presentation of spatial distribution of sound intensity vectors risen close to vibrating ship cabin partitions and inside the cabin will be shown in 2D and 3D graphical form. As a result, a two-dimensional acoustic wave flow map of time-averaged active intensity vectors propagated along curved streamlines and a vector perpendicular to measured plane are graphically illustrated. The technique of acoustic vectors decomposition of sound fields described, can enrich the knowledge of the mechanism of acoustic energy flux through ship partitions.

3

Some comments about the existing theory of sound with comparison to the experimental research of vector effects in real-life acoustic near fields

100%

Weyna S.

Archives of Acoustics

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2007

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tom Vol. 32, No. 4

859--870

EN

Classical studies on the descriptions of acoustic field in an area of a near field, in accordance with the relations formulated by Kirchhoff, Huygens or Rayleigh's integral formula, are commonly known. It is also known that typical interference phenomena, such as diffraction and scattering of acoustic waves, appear in an acoustic field of the real sources as a result of mutual reactions of component waves. Today these vector effects of the acoustic wave occurring in the area of a near field can be simple measured directly with the use of a sound intensity technique. This article presents a few examples of the application of a sound intensity technique to the graphic presentation of the spatial distribution of the acoustic power flow over various geometrical shapes of structures located in a three-dimensional half space. The results of these studies contribute to the theory of sound and general knowledge about the physics of flow acoustic phenomena, especially in the near acoustic field. As a result of research, the visualization analysis of the sound intensity flux in 3D space is shown. The visualization of acoustic power flow in real-life acoustic fields can explain many particular energetic effects (scattering, vortex flow, shielding area, etc.), concerning areas where it is difficult to make numerical analysis.

4

Acoustic energy distribution in space around the pipe outlet

100%

Weyna S.

Archives of Acoustics

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2007

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tom Vol. 32, No. 2

387-397

EN

Visualization system, by serving a dual role as a provider of exploration and exposition capabilities, have became indispensable to the analysis of computational fluid dynamics (CFD) results. In the acoustical practice, up until the last two decades, the study of vectors acoustic fields and noise flow visualisation are rather seldom. But direct measurement of the flow intensity sound as the energetic fields and graphically description of the results, can explain a diffraction and scattering phenomena occur on the real noise sources and solved in practical way a lot of engineering problems. Based on the research with intensity technique and using selected visualizations methods, in the publication are demonstrate in graphical form the sound intensity effects in the space around outlet region of cylindrical pipe. The duct model have a partly square and barrel shaped cross-section. The outlet research space was scanning with intensity probe measured the x, y and z components of sound intensity vector. Direct measurement of the acoustic power flow around outlet can explain all diffraction and scattering phenomena occur in this region and the noise generated by inside flow and around outlet of duct is an environmental concern in engineering practice.

5

Multi-Modal Acoustic Flow Decomposition Examined in a Hard Walled Cylindrical Duct

100%

Weyna S. , Mickiewicz W.

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2014

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tom Vol. 39, No. 2

289--296

EN

Flow fields could be of great interest in the study of sound propagation in aeroengines. For ducts with rigid boundaries, the fluid-resonant category may contribute significantly to unwanted noise. An understanding of the multi-modal propagation of acoustic waves in ducts is of practical interest for use in the control of noise in, for example, aero-engines, automotive exhaust and heating or ventilation systems. The purpose of our experiments was to test the acoustic energy transmission of duct modes based on studies carried out by the sound intensity technique. Sound intensity patterns in circular duct are discussed of modal energy analysis with particular reference to proper orthogonal decomposition and dynamic mode decomposition. The authors try to justify some advantages of the sound intensity experimental research in this area. In the paper, the wide-band sound signal propagated from source approximated with loudspeaker in hard-walled duct is imaged using a sound intensity – based approach. For a simple duct geometry, the sound intensity field is examined visually and by performing a modal decomposition greater insight into the acoustic structures is obtained. The image of sound intensity fields below and above “cut-off” frequency region are found to compare acoustic modes which might resonate in duct.

6

Experimental Acoustic Flow Analysis Inside a Section of an Acoustic Waveguide

100%

Weyna S. , Mickiewicz W. , Pyła M. , Jabłoński M.

Archives of Acoustics

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2013

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tom Vol. 38, No. 2

211--216

EN

Noise propagation within ducts is of practical concern in many areas of industrial processes where a fluid has to be transported in piping systems. The paper presents experimental data and visualization of flow in the vicinity of an abrupt change in cross-section of a circular duct and on obstacles inside where the acoustic wave generates nonlinear separated flow and vortex fields. For noise produced by flow wave of low Mach number, laminar and turbulent flows are studied us- ing experimental sound intensity (SI) and laser particle image velocimetry (PIV) technique adopted to acoustics (A-PIV). The emphasis is put on the development and application of these methods for better understanding of noise generation inside the acoustic ducts with different cross-sections. The intensity distribution inside duct is produced by the action of the sum of modal pressures on the sum of modal particle velocities. However, acoustic field is extremely complicated because pressures in non-propagating (cut-off) modes cooperate with particle velocities in propagating modes, and vice versa. The discrete frequency sound is strongly influenced by the transmission of higher order modes in the duct. By under- standing the mechanism of energy in the sound channels and pipes we can find the best solution to noise abatement technology. In the paper, numerous methods of visualization illustrate the vortex flow as an acoustic velocity or sound intensity stream which can be presented graphically. Diffraction and scattering phenomena occurring inside and around the open-end of the acoustic duct are shown.

7

Modified pressure-pressure sound intensity measurement method and its application to loudspeaker set directivity assessment

100%

Mickiewicz W. , Raczyński M. , Mickiewicz W. , Raczyński M.

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8

An experimental research on the noise energy radiated from ship partitions

100%

Weyna S.

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tom Vol. 8, nr 2

18-24

EN

The paper presents an application of the sound intensity (SI) technique to assessing the effects of ship vibrations on the noise energy radiated by ship partitions. Example measurement results are given to illustrate the application of the SI technique to practical problems of the noise abatement on ships. The results are shown in the form of a two and three-dimensional flow map of active intensity vectors, graphically interpreted for the haterogeneous cabin partitions. The measurement technique as well as the way of graphical presentation can enrich the knowledge of the mechanism of acoustic energy flow through the real ship partitions.

9

3D Acoustic Field Intensity Probe Design and Measurements

100%

Kotus J. , Czyżewski A. , Kostek B.

Archives of Acoustics

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2016

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tom Vol. 41, No. 4

701--711

EN

The aim of this paper is two-fold. First, some basic notions on acoustic field intensity and its measurement are shortly recalled. Then, the equipment and the measurement procedure used in the sound intensity in the performed research study are described. The second goal is to present details of the design of the engineered 3D intensity probe, as well as the algorithms developed and applied for that purpose. Results of the intensity probe measurements along with the calibration procedure are then contained and discussed. Comparison between the engineered and the reference commercial probe confirms that the designed construction is applicable to the sound field intensity measurements with a sufficient effectiveness.

10

Modified pressure-pressure sound intensity measurement method and its application to loudspeaker set directivity assessment

100%

Mickiewicz W. , Raczyński M.

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tom Vol. 27, nr 1

181--194

EN

Sound intensity measurements using special sensors in a form of pressure-velocity and pressure-pressure probes are becoming more and more often the method of choice for characterization of sound sources. Its wider usability is blocked by the probes’ costs. This paper is on a possible modification of the well-known pressure-pressure sound intensity measurement method. In the proposed new approach a synchronized measurement procedure using only single microphone is used. The paper presents the basics of the sound intensity theory, a review of currently used methods of intensity measurement and requirements and limitations of the new method. In the proposed approach one microphone and a properly designed positioning system is used. The application of the method to study the directional characteristics of an active loudspeaker system have been described in detail. The obtained results were compared with those of measurements performed with a commercial p-u probe. The paper contains conclusions indicating advantages of the applied method in comparison with standard pressure measurement methods.

11

A System for Acoustic Field Measurement Employing Cartesian Robot

100%

Szczodrak M. , Kurowski A. , Kotus J. , Czyżewski A. , Kostek B.

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tom Vol. 23, nr 3

333--343

EN

A system setup for measurements of acoustic field, together with the results of 3D visualisations of acoustic energy flow are presented in the paper. Spatial sampling of the field is performed by a Cartesian robot. Automatization of the measurement process is achieved with the use of a specialized control system. The method is based on measuring the sound pressure (scalar) and particle velocity(vector) quantities. The aim of the system is to collect data with a high precision and repeatability. The system is employed for measurements of acoustic energy flow in the proximity of an artificial head in an anechoic chamber. In the measurement setup an algorithm for generation of the probe movement path is included. The algorithm finds the optimum path of the robot movement, taking into account a given 3D object shape present in the measurement space. The results are presented for two cases, first without any obstacle and the other - with an artificial head in the sound field.

12

Experimental Acoustic Flow Analysis Inside a Section of an Acoustic Waveguide

88%

Weyna S. , Mickiewicz W. , Pyła M. , Jabłoński M.

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tom 38

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nr 2

13

Multi-Modal Acoustic Flow Decomposition Examined in a Hard Walled Cylindrical Duct

88%

Weyna S. , Mickiewicz W.

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nr 2

14

Zautomatyzowany system do przestrzennego obrazowania pola akustycznego

75%

Mickiewicz W. , Jabłoński M. J.

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tom R. 58, nr 11

920-922

PL

W pracy przedstawiono zautomatyzowany system do przestrzennego obrazowania wektorowego pola akustycznego. Omówiono podstawy jego funkcjonowania wraz z implementacją Zawarto dyskusję dot. optymalizacji stosowanych algorytmów w celu ich przystosowywania do pracy na jednostkach obliczeniowych różnej mocy. Zaprezentowano wizualizacje dla dwóch modeli wykonane za pomocą nowego systemu oraz przeanalizowano osiągnięty zysk czasowy wynikający z jego użycia w porównaniu z systemem wcześniej stosowanym.

EN

In the paper an automatised system for spatial visualisation of the vector acoustic field is presented. There is discussed the theoretical basis of vector acoustic field visualization based on a vector parameter which is the sound intensity (formula (1)). The measuring method and practical implementation of the system which uses an intensity probe - Microflown USP are described. The presented system was created using the LabVIEW programming environment as two virtual instruments. The first virtual instrument integrates the acquisition and positioning blocks based on a DAQ card and a translating unit driver ISEL. The second instrument is responsible for converting the pressure and velocity components into the vector of sound intensity. This part is the most computationally complex operation performed by the system. The paper includes a discussion about optimisation of the used algorithms in order to adapt them to work on different class computing machines. There is proposed a serial and parallel solution of computing the sound intensity (Fig. 1). At the end of the paper a sample visualisation carried out by the new system for two models

15

Overview of the experimental determination of acoustic flow on the basis of sound intensity measurements

75%

Weyna S.

Mechanics and Control

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2014

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tom Vol. 33, no. 1

26--36

EN

A large variety of CFD/CAA hybrid approaches are commonly used today for aero-acoustic engineering applications using equations and the coupling between source and acoustic propagation region. The coupling is usually made using Lighthill 's acoustic analogies and Kirhchoff's acoustic boundary conditions. This paper intends to give answer how the size and shape of the source may be influence on the accuracy of the different coupling methods and their sensitivity. In this way, some experimental investigation was made using sound intensity measurement technique to the graphic presentation of the spatial distribution of the acoustic power flow over various geometrical shapes of structures located in a three-dimensional space. The results of these studies contribute to the theory of sound and general knowledge about the physics of flow acoustic phenomena, especially in the near acoustic field. As a result of research, the visualization analysis of the sound intensity flux in 3D space is shown as flow wave reactions on the presence of obstacles with different shapes. The results of vector flow fields around a rectangular and circular plate, over the cavity and inside a ducts are shown. The visualization of acoustic power flow in real-life acoustic fields can explain many particular energetic acoustic effects like scattering, vortex flow in shielding area, etc., concerning area where it is difficult to make numerical analysis.

XX

Duża różnorodność hybrydowych zastosowań technik CFD/CAA jest dzisiaj powszechnie używanym narzędziem w inżynierskich zastosowaniach aeroakustycznych wykorzystujących równania sprzęgające źródło drgań mechanicznych z polem propagacji akustycznej. Sprzęganie tych obszarów odbywa się zwykle za pomocą akustycznej analogii Lighthilla i akustycznych warunków brzegowych Kirhchoffa. W tej publikacji poszukuje się odpowiedzi, jak wielkość i kształt źródła wpływa na dokładność i wrażliwość różnych metod sprzęgania. W tym celu wykonano kilka badań eksperymentalnych z użyciem techniki pomiaru natężenia dźwięku obrazując przestrzenny rozkład przepływu energii akustycznej w otoczeniu przeszkód o różnych kształtach geometrycznych. Jako rezultaty badań przepływów pokazano reakcje fali akustycznej na różnego kształtu przeszkody wprowadzone w pole przepływowe. W formach graficznych przedstawiono wyniki badań przepływów wokół płaskiej i okrągłej płyty, nad wnęką akustyczną i we wnętrzach przewodów. Wizualizacja przepływu energii akustycznej w połach rzeczywistych może wyjaśnić wiele szczególnych efektów akustycznych, takich jak rozpraszanie i tworzenie się wirów za przeszkodą lub podobne reakcje w obszarach, dla których trudno jest budować modele numeryczne.

16

Konstrukcja charakterystyk dźwięku "mało wrażliwych" na transformacje nieliniowe

75%

Ziębakowski T.

Diagnostyka

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2000

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tom Vol. 23

93-96

PL

Jedną z trudniejszych do wyjaśnienia własności mechanizmu percepcji dźwięku jest stosunkowo niewielki wpływ zniekształceń nieliniowych dźwięku na uświadamiane przez człowieka wrażenia słuchowe. Wiadomo, że wrażenia słuchowe są silnie powiązane z widmem dźwięku, które z kolei jest bardzo podatne na transformacje nieliniowe. W dodatku zakres natężeń dźwięku odbierany przez człowieka jest znaczny, ponad 100 dB, tak więc duży wpływ będą miały również nieliniowości rzędów większych niż 2. W pracy zaprezentowano konstrukcję charakterystyk "mało wrażliwych" na transformacje nieliniowe, utworzonych na bazie dyskretnego widma dźwięku. Konstrukcja ta ma charakter algebraiczny i wykorzystano w niej w zakresie podstawowym elementy teorii reprezentacji grup skończonych. Pokazano, jak można wyjaśnić niektóre zjawiska psychoakustyczne jak np. zjawisko residuum, które polega na utrzymywaniu się słyszenia tonu podstawowego po jego usunięciu, czy zagadnienie niesłyszenia większości tonów nieliniowych (tzw. kombinacyjnych).

17

Automatyczna lokalizacja źródła dźwięku w obecności zakłóceń z wykorzystaniem wektorowych czujników akustycznych

75%

Czyżewski A. , Kotus J.

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tom Vol. 52, nr 1

36-38

PL

W referacie przedstawiono pomysł i praktyczną realizację pasywnego radaru akustycznego do automatycznego lokalizowania i śledzenia źródeł dźwięku w warunkach zakłóceń. Urządzenie składa się z nowego typu wielokanałowych miniaturowych czujników natężeniowych oraz algorytmów cyfrowego przetwarzania sygnałów. Czułość radaru akustycznego została zbadana w warunkach pola swobodnego. Użyto sygnałów testowych takich jak: sygnały tonalne z zakresu od 125 do 16 kHz, szumowe (w tym samym zakresie częstotliwości) oraz o charakterze impulsowym. Uzyskane wyniki pomiarów wskazują, że nawet niewielka wartość stosunku sygnału do szumu była wystarczająca do poprawnego zlokalizowania źródła dźwięku. Informacja o kierunku dobiegania dźwięku może być zastosowana do automatycznego sterowania cyfrową kamerą typu PTZ (Pan Tilt Zoom).

EN

A concept, practical realization and applications of a passive acoustic radar to automatic localization and tracking of sound sources in disturbing conditions were presented in the paper. The device consists of the new kind of multichannel miniature sound intensity sensors and a group of digital signal processing algorithms. The sensitivity of the realized acoustic radar was examined in free sound field. Several kinds of sound signals were used, such as: pure tone from 125 to 16000 Hz, one third octave band noise in the same frequency range and impulsive sounds. As results from experiments, in some cases even the small value of the signal to noise ratio was sufficient to localize sound source correctly. A video PTZ (Pan Tilt Zoom) camera can be pointed automatically to the spot the detected acoustical source is localized.

18

Visualization methods of sound flow in the 3D real-live field

75%

Weyna S.

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tom Vol. 52, nr 1

16-18

EN

Based on the research with intensity technique and using selected visualizations methods, in the publication are demonstrating few examples of vector space distribution of the real acoustic field, illustrate the application of the Sl measurement for practical problems at the acoustical diagnostic and noise abatement. Analysis of the results makes it possible to obtain much new information about energetic and geometric distributions of the acoustic fields. The measurement technique described, as well as the method of graphical presentation of results, can enrich the knowledge of the mechanism of acoustic energy flux through the real partitions. The article presents the application of Sl technique to graphic visualization of spatial distribution the acoustic energy flow over the barriers of various geometrical shapes structures located in a three-dimensional space.

PL

W oparciu o wyniki badań prowadzonych techniką natężeniową i wykorzystanie metod wizualizacji, w przedstawionej pracy pokazano kilka przykładów rozkładu wektorowych pól akustycznych. Pokazano, jak przydatna staje się technika pomiaru natężenia dźwięku (Sl) w pozyskiwaniu nowych informacji o rozkładach energii w polu akustycznym. Stosując technikę natężeniową do obrazowania przepływów akustycznych, możemy znacznie poszerzyć wiedzę o tych zjawiskach. Artykuł przedstawia zastosowanie techniki Sl do przestrzennej wizualizacji przepływów energii wokół barier o różnej geometrii. Rezultaty badań pokazują rozkłady strumienia natężenia w płaszczyźnie (2D) i w przestrzeni (3D w formie linii strumienia, jako kształty czoła fali, lub izopowierzchnie natężenia.

19

Monitoring środowiska akustycznego w miejscowości Kolbuszowa w 2011 r.

75%

Piechowicz B. , Stawarczyk K. , Stawarczyk M.

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tom Nr 1(8)

45-51

PL

W okresie od lutego do września 2011 r. wykonywano pomiary poziomu dźwięku w sześciu reprezentatywnych dla danego typu zabudowy i użytkowania punktach miasta Kolbuszowa. Tak pora doby, jak i lokalizacja miejsca pomiarowego miały znaczący wpływ na środowisko akustyczne badanego obszaru. Analizy potwierdziły również, że w niektórych punktach miasta normy emisji dźwięków zostały znacznie przekroczone.

EN

From February to September 2011 measurements of sound levels in six representative areas in town of Kolbuszowa were made. It was found that in the studied region the time of day and measurement location had a strong impact on the acoustic environment. The research also confirmed that in some places in the town the sound emission standards were considerably exceeded.

20

Assessment of energetistic measuring techniques and their application to diagnosis of acoustic condition of hydraulic machinery and equipment

63%

Osiński P. , Kollek W.

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tom Vol. 13, no. 3

313--321

EN

Energy methods in acoustic were introduced more than 40 years ago but new techniques of data analyses can give new possibility for hydraulic system health assessment. Possibilities of applying energetistic techniques to the measurement of complex vibroacoustic processes are presented using as an example a hydraulic feeder. These research methods open up new prospects for the reduction of noise emission in hydraulic machinery and equipment. The described vector techniques of locating sound sources by means of an acoustic probe and a measuring plane antenna deserve special attention. As a result of the measurement a distribution of the intensity of emissions originating from different parts of the source is obtained in the form of emission maps. The techniques can be applied to any object (e.g. a pump, a motor) to determine the main sources of noise emission and then this information can be used to improve the object's design. This paper is based on research in the fields of the design and operation of hydraulic systems, conducted for many years in the Institute of Machine Design and Operation at Wrocław University of Technology.