Estimating Surface Acoustic Impedance With the Inverse Method

Piechowicz, Janusz

doi:10.1080/10803548.2011.11076893

Cited by 6 publications

(7 citation statements)

References 6 publications

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“…Determination of the acoustic impedance values for the bounding surfaces was based on a measurement of acoustic pressure values in selected reception points located inside the model room and a simultaneous measurement of the signal phase shifts with respect to the stimulation signal (Piechowicz, 2011).…”

Section: Determination Of the Acoustic Impedance Of The Model Surfacementioning

confidence: 99%

Estimation of Acoustic Impedance for Surfaces Delimiting the Volume of an Enclosed Space

Piechowicz¹,

Czajka²

2012

Archives of Acoustics

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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.

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Section: Determination Of the Acoustic Impedance Of The Model Surfacementioning

confidence: 99%

Estimation of Acoustic Impedance for Surfaces Delimiting the Volume of an Enclosed Space

Piechowicz¹,

Czajka²

2012

Archives of Acoustics

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“…A meshless, direct method to determine unknown boundary conditions to the Helmholtz problem was proposed by Jin & Zheng [10] relying on the method of fundamental solutions and truncated singular value decomposition regularization. Piechowicz et al [11,12,13] have developed a numerical scheme that relies on a boundary element method applied to the Helmholtz-Kirchoff equation to evaluate the acoustic impedance of obstacles and/or boundaries internal to a closed domain from pressure information taken at a finite set of interior points. To the best of authors' knowledge no prior work has tackled the evaluation of the spatial distribution of the broadband acoustic impedance (2) over one or multiple boundaries of a computational domain without the use of regularization or iterative techniques.…”

Section: Introductionmentioning

confidence: 99%

“…The acoustic properties of a system are typically investigated via Helmholtz solvers, which rely on an eigenvalue formulation (12), hence yielding a discrete set of complex eigenvalues and eigenvectors containing frequency and growth rate, and resonant waveform information respectively. Such approach requires homogeneous boundary conditions to be assigned everywhere (figure 3a).…”

Section: Introductionmentioning

confidence: 99%

Surface Impedance Determination via Numerical Resolution of the Inverse Helmholtz Problem

Patel

Gupta

Scalo

2017

23rd AIAA/CEAS Aeroacoustics Conference

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Assigning boundary conditions, such as acoustic impedance, to the frequency domain thermoviscous wave equations (TWE), derived from the linearized Navier-Stokes equations (LNSE) poses a Helmholtz problem, solution to which yields a discrete set of complex eigenfunctions and eigenvalue pairs. The proposed method -the inverse Helmholtz solver (iHS) -reverses such procedure by returning the value of acoustic impedance at one or more unknown impedance boundaries (IBs) of a given domain, via spatial integration of the TWE for a given real-valued frequency with assigned conditions on other boundaries. The iHS procedure is applied to a second-order spatial discretization of the TWEs on an unstructured staggered grid arrangement. Only the momentum equation is extended to the center of each IB face where pressure and velocity components are co-located and treated as unknowns. The iHS is finally closed via assignment of the surface gradient of pressure phase over the IBs, corresponding to assigning the shape of the acoustic waveform at the IB. The iHS procedure can be carried out independently for different frequencies, making it embarrassingly parallel, and able to return the complete broadband complex impedance distribution at the IBs in any desired frequency range to arbitrary numerical precision. The iHS approach is first validated against Rott's theory for viscous rectangular and circular ducts. The impedance of a toy porous cavity with a complex geometry is then reconstructed and validated with companion fully compressible unstructured Navier-Stokes simulations resolving the cavity geometry. Verification against one-dimensional impedance test tube calculations based on time-domain impedance boundary conditions (TDIBC) is also carried out. Finally, results from a preliminary analysis of a thermoacoustically unstable cavity are presented.

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“…The Faculty develops the most up-to-date domains of mechanics including vibroacoustics which combine the problems of the theory of linear vibrations (Kasprzyk, 2011;Wiciak, Trojanowski, 2014), engineering dynamics, theoretitical acoustics (Snakowska, Jurkiewicz, 2010;Rdzanek et al, 2011), and technical acoustics (Piechowicz, 2011;Barański, Wszołek, 2013). Research is carried out in the areas connected with the problems of propagation of the noise produced by road traffic, wind power plants (Kasprzak et al, 2014;Wszołek et al, 2014), and industry, especially ducted systems with flow (Jurkiewicz et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Technical Note. Optimization of Parameters for a Damped Oscillator Excited by a Sequence of Random Pulses

Ozga¹

2015

Archives of Acoustics

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The paper is another step in discussion concerning the method of determining the distributions of pulses forcing vibrations of a system. Solving a stochastic problem for systems subjected to random series of pulses requires determining the distribution for a linear oscillator with damping. The goal of the study is to minimize the error issuing from the finite time interval. The applied model of investigations is supposed to answer the question how to select the parameters of a vibrating system so that the difference between the actual distribution of random pulses and that determined from the waveform is as small as possible.

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Estimating Surface Acoustic Impedance With the Inverse Method

Abstract: room acoustics sound absorption coefficient acoustic impedance

Cited by 6 publications

References 6 publications

Estimation of Acoustic Impedance for Surfaces Delimiting the Volume of an Enclosed Space

Estimation of Acoustic Impedance for Surfaces Delimiting the Volume of an Enclosed Space

Surface Impedance Determination via Numerical Resolution of the Inverse Helmholtz Problem

Technical Note. Optimization of Parameters for a Damped Oscillator Excited by a Sequence of Random Pulses

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