Temat: acoustic impedance - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Optimal Selection of Multicomponent Matching Layers for Piezoelectric Transducers using Genetic Algorithm
Autorzy:: Gudra, Tadeusz
Banasiak, Dariusz
Powiązania:: https://bibliotekanauki.pl/articles/1953531.pdf
Data publikacji:: 2021
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:: acoustic impedance
matching layers
ultrasonic transducers
Opis:: One major problem in the design of ultrasonic transducers results from a huge impedance mismatch between piezoelectric ceramics and the loading medium (e.g. gaseous, liquid, and biological media). Solving this problem requires the use of a matching layer (or layers). Optimal selection of materials functioning as matching layers for piezoelectric transducers used in transmitting and receiving ultrasound waves strictly depends on the type of the medium receiving the ultrasound energy. Several methods allow optimal selection of materials used as matching layers. When using a single matching layer, its impedance can be calculated on the basis of the Chebyshev, DeSilets or Souquet criteria. In the general case, the typically applied methods use an analogy to a transmission line in order to calculate the transmission coefficient T. This paper presents an extension of transmission coefficient calculations with additional regard to the attenuation coefficients of particular layers. The transmission coefficient T is optimised on the basis of a genetic algorithm method. The obtained results indicate a significant divergence between the classical calculation methods and the genetic algorithm method.
Źródło:: Archives of Acoustics; 2020, 45, 4; 699-707
0137-5075
Pojawia się w:: Archives of Acoustics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Estimation of Acoustic Impedance for Surfaces Delimiting the Volume of an Enclosed Space
Autorzy:: Piechowicz, J.
Czajka, I.
Powiązania:: https://bibliotekanauki.pl/articles/177215.pdf
Data publikacji:: 2012
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:: acoustic impedance
acoustic measurements
numerical methods
sound field
Opis:: Several methods can be applied for analyses of the acoustic field in enclosed rooms namely: wave propagation, geometrical or statistical analysis. The paper presents problems related to application of the boundary elements method to modelling of acoustic field parameters. Experimental and numerical studies have been combined for evaluation of acoustic impedance of the material used for the walls of a model room. The experimental studies have been carried out by implementing a multichannel measuring system inside the constructed model of an industrial room. The measuring system allowed simultaneous measurements of the source parameters – the loudspeaker membrane vibration speed, the acoustic pressure values in reception points located inside the model space as well as phase shifts between signals registered in various reception points. The numerical modelling making use of the acoustic pressure values measured inside the analyzed space allowed determination of requested parameters of the surface at the space boundary.
Źródło:: Archives of Acoustics; 2012, 37, 1; 97-102
0137-5075
Pojawia się w:: Archives of Acoustics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Estimating Surface Acoustic Impedance With the Inverse Method
Autorzy:: Piechowicz, J.
Powiązania:: https://bibliotekanauki.pl/articles/90473.pdf
Data publikacji:: 2011
Wydawca:: Centralny Instytut Ochrony Pracy
Tematy:: room acoustics
sound absorption coefficient
acoustic impedance
Opis:: Sound field parameters are predicted with numerical methods in sound control systems, in acoustic designs of building and in sound field simulations. Those methods define the acoustic properties of surfaces, such as sound absorption coefficients or acoustic impedance, to determine boundary conditions. Several in situ measurement techniques were developed; one of them uses 2 microphones to measure direct and reflected sound over a planar test surface. Another approach is used in the inverse boundary elements method, in which estimating acoustic impedance of a surface is expressed as an inverse boundary problem. The boundary values can be found from multipoint sound pressure measurements in the interior of a room. This method can be applied to arbitrarily-shaped surfaces. This investigation is part of a research programme on using inverse methods in industrial room acoustics.
Źródło:: International Journal of Occupational Safety and Ergonomics; 2011, 17, 3; 271-276
1080-3548
Pojawia się w:: International Journal of Occupational Safety and Ergonomics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Sound Radiation of a Pulsating Sphere in the Outlet of a Hard/Soft Semi-Spherical Cavity in a Flat Screen
Autorzy:: Rdzanek, W.
Powiązania:: https://bibliotekanauki.pl/articles/950213.pdf
Data publikacji:: 2016
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:: Neumann/Dirichlet problem
sound field
acoustic impedance
continuity
Opis:: A rigorous analysis of sound radiation by a pulsating sphere forming a resonator together with a semispherical cavity is presented. Both hard and soft boundaries are considered, as well as mixed. The problem is solved by dividing the entire region into two subregions, one surrounding the sphere and containing the cavity and the other for the remaining half-space. The continuity conditions are applied to obtain the acoustic pressure. Then the acoustic radiation resistance is calculated both in the near- and far-field. The acoustic radiation reactance is calculated in the impedance approach. The resonance frequencies are determined, for which a significant growth of the sound pressure level is observed as well as the sound field directivity. The accuracy and convergence of these rigorous results has been examined empirically.
Źródło:: Archives of Acoustics; 2016, 41, 1; 75-86
0137-5075
Pojawia się w:: Archives of Acoustics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Recognition of anhydrite intercalated salt deposit from seismic dataset distorted by noise
Autorzy:: Kawalec-Latała, E.
Powiązania:: https://bibliotekanauki.pl/articles/178911.pdf
Data publikacji:: 2015
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:: underground storage
acoustic impedance
salt deposit
inhomogeneity detection
noise
Opis:: Acoustic inversion is useful to extract information from seismic data. Inhomogeneities of salt deposits should be predicted before the decision of underground storage location is made. The work concerns the possibility of detecting anhydrite intercalation in the rock salt from seismic dataset. The resolution strongly depends on signal to noise ratio. The synthetic pseudoacoustic impedance sections are generated for efficiency test of predictive and minimum entropy deconvolution process, when random noise distorts the seismic traces.
Źródło:: Studia Geotechnica et Mechanica; 2015, 37, 3; 41-48
0137-6365
2083-831X
Pojawia się w:: Studia Geotechnica et Mechanica
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Research of acoustical impedance of human skin
Autorzy:: Plaskota, Przemysław
Powiązania:: https://bibliotekanauki.pl/articles/127723.pdf
Data publikacji:: 2019
Wydawca:: Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:: acoustic impedance
human skin
HRTF
impedancja akustyczna
skóra człowieka
Opis:: This paper presents the methodology of measuring acoustic impedance of human skin and discusses the results of the tests. Measurement of the acoustic impedance of human skin is a complex issue. The most difficult thing is related to the nature of the object of research. Cooperation of volunteer participating in the experiment is crucial in collecting accurate data. Appropriate measuring conditions must be provided because of the length of time required to conduct measurement. The Kundt tube method has been used as a research technique applied for evaluation of the material impedance. It was assumed that the results would differ with regard to different points chosen for measurement, located on the body of volunteer as well as with regard to the features of the skin structure of the volunteers participating in this experiment. Results have revealed that for different people similar parameters have been obtained. Moreover, results are alike for various measured points localized on person’s body.
Źródło:: Vibrations in Physical Systems; 2019, 30, 1; 1-6
0860-6897
Pojawia się w:: Vibrations in Physical Systems
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Obliczanie objętości materii organicznej (TOC) na podstawie inwersji genetycznej danych sejsmicznych
Calculation of organic matter volume (TOC) based on genetic inversion of seismic data
Autorzy:: Bartoń, R.
Wilk, A.
Powiązania:: https://bibliotekanauki.pl/articles/1835240.pdf
Data publikacji:: 2018
Wydawca:: Instytut Nafty i Gazu - Państwowy Instytut Badawczy
Tematy:: TOC
inwersja genetyczna
impedancja akustyczna
shale gas
genetic inversion
acoustic impedance
Opis:: W artykule została zaprezentowana metodyka wyznaczania rozkładu parametru TOC na danych sejsmicznych 3D na podstawie inwersji genetycznej. Zaprezentowany schemat obliczeń zastosowano na danych sejsmicznych pochodzących z obszaru północnej Polski. Głównym celem przeprowadzonych badań było rozpoznanie dwóch, wyinterpretowanych horyzontów sejsmicznych (z których pierwszy odpowiadał powierzchni stropowej ogniwa Jantaru, a drugi stropowi formacji z Sasina), pod kątem wyznaczenia stref potencjalnych sweet spotów. Wyinterpretowany rozkład parametrów fizycznych takich jak: prędkość i gęstość, oraz parametrów petrofizycznych takich jak: porowatość, nasycenie, a także TOC w obrębie kolejnych sekwencji skalnych, ma ścisły związek z parametrami sejsmicznymi, takimi jak czasy przejścia fal odbitych od poszczególnych granic sejsmicznych oraz ich charakterystyk amplitudowych i częstotliwościowych [1, 8]. Zaprezentowana metodyka wyznaczania rozkładu parametru TOC była realizowana na podstawie zmienności amplitud pola falowego, pola prędkości fal podłużnych oraz pomiarów labolatoryjnych TOC w otworach wiertniczych. Uzyskane wyniki w postaci map i rozkładów przestrzennych pozwalają zidentyfikować obszary perspektywiczne o podwyższonych wartościach TOC, a ich dokładność uwarunkowana jest rozdzielczością danych sejsmicznych.
The article presents the methodology for determining the distribution of TOC parameter on 3D seismic data, based on genetic inversion. The presented calculation scheme was applied on seismic data from the northern area of Poland. The main goal of the study was to recognize two seismic horizons (the first of which corresponded to the top surface of the Jantar Member and the second to the top of the Sasino Formation), in terms of designating the zones of potential sweet spots. The interpreted distribution of physical parameters such as: velocity and density and petrophysical parameters, such as: porosity, saturation and TOC within successive rock sequences, is closely related to seismic parameters, such as transition times of waves reflected from individual seismic boundaries and their amplitude characteristics and frequency [1, 8]. The presented methodology for determining the distribution of the TOC parameter, was based on the variability of the wave field amplitudes, the field of longitudinal wave velocities and laboratory TOC measurements in wellbores. Obtained results in the form of maps and spatial distributions allow to identify perspective areas with increased TOC values, and their accuracy is conditioned by the resolution of seismic data.
Źródło:: Nafta-Gaz; 2018, 74, 6; 415-422
0867-8871
Pojawia się w:: Nafta-Gaz
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: The acoustic radiation impedance of a circular membrane vibrating near the three-wall corner
Autorzy:: Rdzanek, W. P.
Rdzanek, W. J.
Szemela, K.
Powiązania:: https://bibliotekanauki.pl/articles/331634.pdf
Data publikacji:: 2008
Wydawca:: Polskie Towarzystwo Akustyczne
Tematy:: sound radiation
acoustic radiation impedance
circular membrane
Opis:: A flat circular membrane is located near the three- wall corner, limited by the three rigid baffles arranged perpendicularly to each other. The problem of sound radiation has been solved using the spectral form of the Green function for this Neumann boundary value problem together with the complete eigenfunction system of the axisymmetric and asymmetric modes of the membrane is excited by a surface vibrating harmonically with respect to time within the vacuum. The membrane is excited by a surface force. The acoustic attenuation 3399effect has been taken into account as well as the influence of the corner baffles. The resultant sound pressure and the resultant acoustic impedance have been presented as their eigenfunction series. The modal, self and mutual, radiation resistance has been presented in the form of the approximation valid within the low frequency vibration range. The low frequency approximation for the modal radiation reactance has been obtained on the basis of the radiation resistance using the Hilbert transform.
Źródło:: Hydroacoustics; 2008, 11; 339-352
1642-1817
Pojawia się w:: Hydroacoustics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Evaluation of the Acoustic Performance of Porous Materials Lined Ducts with Geometric Discontinuities
Autorzy:: Tounsi, Dhouha
Taktak, Wafa
Dhief, Raja
Taktak, Mohamed
Chaabane, Mabrouk
Haddar, Mohamed
Powiązania:: https://bibliotekanauki.pl/articles/2141657.pdf
Data publikacji:: 2022
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:: geometric discontinuities in duct systems
acoustic impedance
porous materials
perforated plate
acoustic power attenuation
Opis:: Duct silencers provide effective noise reduction for heating, ventilation and air conditioning systems. These silencers can achieve an excellent sound attenuation through the attributes of their design. The reactive silencer works on the principle of high reflection of sound waves at low frequencies. On the other hand, the dissipative silencer works on the principle of sound absorption, which is very effective at high-frequencies. Combining these two kinds of silencers allowed covering the whole frequency range. In this paper, the effect of liner characteristics composed of a perforated plate backed by a porous material and geometry discontinuities on the acoustic power attenuation of lined ducts is evaluated. This objective is achieved by using a numerical model to compute the multimodal scattering matrix, thus allowing deducing the acoustic power attenuation. The numerical results are obtained for six configurations, including cases of narrowing and widening of a radius duct with sudden or progressive discontinuities. Numerical acoustic power attenuation shows the relative influence of the variation in the values of each parameter of the liner, and of each type of radius discontinuities of ducts.
Źródło:: Archives of Acoustics; 2022, 47, 2; 223-240
0137-5075
Pojawia się w:: Archives of Acoustics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: The impact of regular diving on the condition of the middle ear
Autorzy:: Stieler, Olgierd
Loba, Wawrzyniec
Gawęcki, Wojciech
Urbaniak-Olejnik, Marta
Majewska, Anna
Warchoł, Wojciech
Hojan-Jezierska, Dorota
Powiązania:: https://bibliotekanauki.pl/articles/2093855.pdf
Data publikacji:: 2021-12-13
Wydawca:: Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
Tematy:: tympanometry
middle ear
high pressure
wideband tympanometry
scuba diving
acoustic impedance tests
Opis:: ObjectivesIt is generally held that exposure to both high-pressure and long-lasting contact with water makes diving a potentially hazardous sports activity as far as the ears are concerned. There is a number of research investigating the condition of the middle ear in a short period following diving; however, the knowledge regarding the long-term effects of regularly repeated diving remains limited.Material and methodsThe aim of this study is to evaluate the function of the middle ear after a diving season in a group of 31 adults diving regularly (1–17 years) by means of the following methods: 1) interview, 2) otoscopy, 3) pure tone audiometry, 4) classic tympanometry, and 5) wideband tympanometry.ResultsPeriodic problems with pressure equalization in the middle ear were observed in 12 individuals (38.7%). In all the analyzed cases, the authors found a normal condition of the external auditory canal and the tympanic membrane in otoscopy, normal hearing in pure tone audiometry, curve type A, and normal gradient in both classic and wideband tympanometry. Conclusions: Safe diving (according to safety precautions) does not have any long-term negative effects on the condition of the middle ear. However, these observations should be verified in a larger group of divers.
Źródło:: International Journal of Occupational Medicine and Environmental Health; 2021, 34, 6; 779-788
1232-1087
1896-494X
Pojawia się w:: International Journal of Occupational Medicine and Environmental Health
Dostawca treści:: Biblioteka Nauki

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