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1
Content available Comparison analysis of noise generated by wind turbines with the other noise source in outdoor environment
Staniek Andrzej, Kompała Janusz, Bramorska Alicja, Bartmański Cezary
Vibrations in Physical Systems
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2023
|
Vol. 34, nr 1
art. no. 2023108
EN
The paper presents a comparison analysis of the noise generated by wind turbines and the one generated by a ventilation shaft of a working coal mine. The aim of the research was to compare the frequency and amplitude distribution of those sources, especially in the infra range. The ultimate aim it is evaluate possible environmental impact on human annoyance or severity. During the research noise signals were recorded utilizing low frequency microphones, shielded by windscreens. Microphones were localized at the heights of 0.0 m, 1.5 m (approximate location of a human ear in a standing position) and 4 m. Additionally, a measurement position of a microphone in relation to the ground surface was observed. Measurements at ground level were performed according to the standard PN-EN 61400-11:2013-07 and in vertical position, where the microphone was mounted "upside down" with the grid flush with the board. The possible influence of wind speed was also monitored. The results of the measurements are discussed.
2
Content available Acoustic Modelling of Sport and Hunting Shooting Ranges in the Aspect of Shaping Noise Emissions Into the Environment
Boczkowski Arkadiusz
Multidisciplinary Aspects of Production Engineering
|
2020
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Vol. 3, Iss. 1
308--319
EN
The article deals with the problem of acoustic modelling of sport and hunting shooting ranges for the purposes of carrying out acoustic impact assessments on the environment. The fashion for recreational shooting and the dynamic development of shooting ranges resulted in conflict situations between the shooting range and the residents. Increasingly, the condition for allowing the shooting range to be used is to carry out an acoustic analysis to confirm the lack of noise nuisance. Therefore, it is necessary to develop guidelines for acoustic modelling of shooting ranges, taking into account their purpose and types of shooting axes. Each of the shooting axes is designed for a different type of shooting and thus has different acoustic characteristics. In the article, the author presents a method of modelling noise emissions from the shooting range on the example of one of the popular shooting competitions which is the hunting trap. First, acoustic measurements of the unit noise source related to the firing of shots by a firearms shooter were made. Then the directional characteristics of this source were determined, the shooting axis of the “hunting trap” type was modelled during a typical shooting competition and its directionality was determined. Then, on the example of a specific shooting range, the possibility of using the results to analyse the propagation of noise into the environment during typical shootings on the trap axis was presented.
3
Content available Tuning the selected acoustic helicoidal resonator with a short flat bar - numerical analysis
Łapka Wojciech
Vibrations in Physical Systems
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2019
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Vol. 30, nr 1
art. no. 2019140
EN
This paper describes the possible way of tuning the selected acoustical helicoidal resonator placed in straight cylindrical duct by the use of a short flat bar. The acoustic attenuation performance (transmission loss) of helicoidal resonator has emphatically changed with the change of the length and the degree of rotation of a short flat bar placed close to the resonator. The finite element numerical calculations of the acoustical systems were made in COMSOL Multiphysics computational environment. The results show that the change of length and rotation of short flat bar can widely change the resonance frequencies of helicoidal resonator. So in this work were presented the possible simple tuning options for the acoustic helicoidal resonator applied in ducted systems.
4
Content available Numerical analysis of sound propagation in selected acoustical system with helicoidal resonator placed in cylindrical duct with 90 degree elbow
Łapka W.
Vibrations in Physical Systems
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2018
|
Vol. 29
art. no. 2018018
EN
This paper concerns to the numerical analysis of transmission loss of selected acoustical helicoidal resonator placed in cylindrical duct close to the elbow. The change of acoustic attenuation performance of helicoidal resonator is observed with the change of the degree of rotation of cylindrical duct elbow. The finite element method was used to calculate the acoustical system in the COMSOL Multiphysics computational environment. The results show that the change of rotation of elbow or rotation of helicoidal profile can change the resonance frequency, and thus the tuning options are extended when applying helicoidal resonators in ducted systems.
5
Content available Nonlinear phenomena of small-scale sound in a gas with exponential stratification
Perelomova A.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2017
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Vol. 21, No 2
135--147
EN
The nonlinear dynamics of perturbations, quickly varying in space, with comparatively large characteristic wavenumbers k: k > 1/H, is considered. H is the scale of density and pressure reduction in unperturbed gas, as the coordinate increases (H is the so-called height of the uniform equilibrium gas). Coupling nonlinear equations which govern the sound and the entropy mode in a weakly nonlinear flow are derived. They describe the dynamics of the gas in the leading order, with an accuracy up to the terms k(H)-1. In the field of the dominative sound mode, other induced modes contain parts which propagate approximately with their own linear speeds and the speed of the dominative mode. The scheme of successive approximations of nonlinear links between perturbations in the progressive mode is established. The numerical calculations for some kinds of impulses confirm the theory.
6
Content available remote Monitoring hałasu środowiskowego
Żuchowski R., Nowoświat A., Dulak L.
Izolacje
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2016
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R. 21, nr 4
20--27
PL
W artykule przedstawiono zagadnienia związane z akustyką środowiskową. Omówiono stosowane oznaczenia i definicje, zagadnienia prawne oraz założenia przyjmowane podczas obliczania hałasu środowiskowego, w tym podczas tworzenia map akustycznych.
EN
The article presents certain environmental acoustics issues. It discusses the applied identifications and definitions, legal issues, and assumptions used for environmental noise calculations, including drafting of acoustic maps.
7
Content available Performance of Noise Map Service Working in Cloud Computing Environment
Marciniuk K., Szczodrak M., Kostek B.
Archives of Acoustics
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2016
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Vol. 41, No. 2
297--302
EN
In the paper, a noise map service designated for the user interested in environmental noise is presented. Noise prediction algorithm and source model, developed for creating acoustic maps, are working in the cloud computing environment. In the study, issues related to the noise modelling of sound propagation in urban spaces are discussed with a particular focus on traffic noise. Examples of results obtained through a web application created for that purpose are shown. In addition, these are compared to results obtained from the commercial software simulations based on two road noise prediction models. Moreover, the computing performance of the developed application is investigated and analyzed. In the paper, a flowchart simulating the operation of the noise web-based service is presented showing that the created application is easy to use even for people with little experience in computer technology.
8
Content available Tracking of the broadband source of the underwater noise in the very shallow water conditions
Grelowska G., Kozaczka E.
Hydroacoustics
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2015
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Vol. 18
77--86
EN
The paper contains the results, both theoretical and experimental, connected with the tracking of the underwater noise source as small ships, pontoon, diver and so on. The problem of security in the shallow water area is the challenge for underwater acousticians. In this paper there is taken into account the detection of the sources that move on the surface of the sea or underwater in shallow and very shallow water. The main goal deals with characterization of the sound propagation at the shallow water channel. The next problem is formulation of the sound propagation inside of this acoustic duct including normal mode creations and dispersion of the acoustic energy. When we take into account the small ships noise the two main sources are analyzed. The first one is the vibration energy produced by the mechanisms located inside of the ship hull. The acoustical energy is transformed through structural elements of the hull to surrounding water. This energy propagates as broadband underwater noise. The next source is the ship propeller. The sources of the underwater noise give the some deposit to the total acoustical energy that means the ambient noise. The problem that should be solved is to discover these acoustical disturbances along with their classification, identification and tracking.
9
Content available Underwater Noise Generated by a Small Ship in the Shallow Sea
Grelowska G., Kozaczka E., Kozaczka S., Szymczak W.
Archives of Acoustics
|
2013
|
Vol. 38, No. 3
351--356
EN
Study of the sea noise has been a subject of interest for many years. The first works in this scope were published at the turn of the twentieth century by Knudsen (Knudsen et al., 1948) and G. Wenz (Wenz, 1962). Disturbances called “shipping noise” are one of the important components of the sea noise. In this work the results of an experimental research of underwater noise produced by a small ship of a classic propulsion are presented. A linear receiving antenna composed of two orthogonal components was used in the investigation. Identification of the main sources of acoustic waves related with the ship was achieved. In addition, the intensity of the wave was measured. The research was performed in conditions of the shallow sea.
10
Propagacja dźwięku w atmosferze
Kaiser K.
Technika Chłodnicza i Klimatyzacyjna
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2009
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nr 3
107-113
PL
Tematem artykułu jest propagacja dźwięku w atmosferze. Jest to zjawisko bardzo złożone i zależne od wielu różnych czynników nakładających się jednocześnie w tym samym czasie. W części wstępnej publikacji przybliżone zostały takie pojęcia, jak: hałas aerodynamiczny i hałas mechaniczny, zagadnienie szacowania sił wzbudzających drgania, a także pojęcie fali płaskiej i sferycznej. Zwrócona została uwaga na problem tłumienia naturalnego i propagację fal dźwiękowych w swobodnej atmosferze. Zaprezentowano modele, sferyczny i cylindryczny propagacji dźwięku w przestrzeni otwartej. Emisja hałasu do atmosfery z układów klimatyzacji i wentylacji związana jest przede wszystkim z działaniem wentylatorów znajdujących się na zewnątrz budynku, co jest niewątpliwie uciążliwe dla otoczenia. Przedstawione w artykule modele pozwalają przewidzieć intensywność dźwięku w zależności od odległości obserwatora od źródła.
EN
The paper deals with propagation of sound in air. This is complex phenomenon depending of a set of various simultaneous effects. The basic concepts have been described: aerodynamical and mechanical noise, problem of estimation of forces generating vibrations, as well as the fiat and spherical sound waves. A close attnetion has been paid to natural damping as well as sound wave propagation in free air. Theoretical models of a flat and spherical sound wave propagation have been presented. Sound emission from the air-conditioning and ventilation systems to air due to operation of fans outside the building have been discussed. The models presented in the papers enable to predict sound intensity depending on the distance from sound source.
11
Generacja i propagacja dźwięku w zaworach regulacyjnych instalacji wodnych
Kaiser K.
Technika Chłodnicza i Klimatyzacyjna
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2009
|
nr 2
71-77
12
Content available remote Weakly nonlinear dynamics of short acoustic waves in exponentially stratified gas
Perelomova A.
Archives of Acoustics
|
2009
|
Vol. 34, No. 2
197-213
EN
The types of linear motion over an ideal gas affected by gravity are specified approximately in the case of large characteristic wave number of perturbation k: k>> 1/H, where H is the scale of density and pressure decrease of the background gas, the so-called height of the uniform gas. The corresponding approximate operators projecting the overall vector of perturbations into specific types are derived, along with equations governing sound in a weakly nonlinear flow. The validity of approximate formulae are verified for the concrete examples of initial waveforms. The numerical analysis reveals a good agreement of these approximate expressions with the exact ones obtained previously by the author. The analysis applies to the weakly nonlinear flow as well, with the small Mach numbers (M<<1). The links inside modes are redetermined by including terms of order M2 and M2/kH.
13
Content available Noise Reduction of Spiral Ducts
Łapka W., Cempel C.
International Journal of Occupational Safety and Ergonomics
|
2007
|
Vol. 13, No. 4
419--426
EN
The paper presents noise reduction (NR) of spiral ducts as a result of computational modeling of acoustic wave propagation. Three-dimensional models were created with the finite element method in COMSOL Multiphysics version 3.3. Nine models of spiral ducts with 1–9 spiral leads were considered. Time-harmonic analysis was used to predict NR, which was shown in spectral and interval frequency bands. Spiral duct performance can be seen as a comparison of NR before and after a change from a circular to a spiral duct.
14
Sound propagation problem solved by boundary elements method
Szweda J.
Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska
|
2006
|
z. 31
149-153
EN
This article deals the numerical method to solution of sound propagation radiated by vibration of surfaces of machine complex. As the base of applied numerical solution is used the boundary elements method. The purpose of the work is to determine the rate of inaccuracy of numerical results obtained using the simple approach of BEM and also the estimation of its usability to finding the acoustical properties of machine parts. To fulfil the purpose the solution of acoustic problem was done using two approach of BEM. The average relative error of acoustic pressure level has value about 5%, , unique maximum value is 16 %.
15
Pogłosowość sali kinowej jako pochodna kształtu sufitu
Jabłoński M., Szer J.
Przegląd Prac Badawczych Zespołu Budownictwa Ogólnego i Konstrukcji Drewnianych
|
2005
|
Z. 6
33--41
PL
Przedmiotem rozważań jest pomieszczenie usytuowane w budynku SDS Politechniki Łódzkiej przy Al. Politechniki 3a. Wykorzystywane jest głównie jako sala kinowa . Użytkownik Sali podjął decyzję o rozszerzeniu funkcji użytkowej tego pomieszczenia i docelowo usytuowanie w nim Sali kinowej, widowiskowej oraz konferencyjnej. Projekty architektoniczne przebudowy Sali różniły się nieznacznie. Elementem, który różnił poszczególne projekty była konstrukcja sufitu. Ponieważ sufit odgrywa istotną rolę w akustyce wnętrz, powstała konieczność oceny poprawności rozwiązań architektonicznych pod kątem wymagań akustycznych. Pozwolił to już na etapie projektowania przewidzieć, jak ukształtuje się naturalna akustyka danego wnętrza.
16
Identyfikacja parametrów i weryfikacja modelu na przykładzie badań nad wykorzystaniem materiałów o strukturze ziarnistej do minimalizacji drgań i hałasu konstrukcji
Klekot G.
Przegląd Mechaniczny
|
2002
|
nr 3
34-39
PL
Przedstawiono rozważania dotyczące przewidywania struktury sygnału akustycznego w otoczeniu maszyny, traktowanej jako źródło dźwięku, przy zastosowaniu elementów konstrukcyjnych w postaci niewielkich wymiarowo, płaskich przegród, zaproponowano zależność, umożliwiającą prognozowanie poziomu ciśnienia akustycznego w różnych punktach z uwzględnieniem efektów spowodowanych modyfikacją własności pola swobodnego, opisano przebieg eksperymentu laboratoryjnego wykonanego w komorze bezechowej z użyciem źródła dźwięku o zadanej strukturze amplitudowo-częstotliwościowej; na konkretnym przykładzie zademonstrowano sposób postępowania prowadzący do identyfikacji parametrów oraz przeprowadzono weryfikację rezultatów modelowania przez porównanie z wynikami badań empirycznych.
EN
Considerations on a likely structure of an acoustic signal around a machine, treated as a source of sound with the application of constructional materials in the form of small size flat partitions. Proposition of a relationship permitting to forecast the acoustic pressure level at various points with an account taken of the effects caused by a modification of the properties of the free field. Description of a laboratory experiment made in an echo-free chamber using a sound source of a known amplitude-frequency structure. A practical procedure to gain an identification of parameters. Verification of the modelling results by comparison with empirical tests.
17
Content available remote Okna z profili PVC i ich izolacyjność akustyczna
Nurzyński J.
Materiały Budowlane
|
2002
|
nr 7
24-27
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