A Review of Acoustical Methods for Porous Material Characterisation

Abstract

The purpose of this paper is to present and discuss a range of in-situ and laboratory methods can be used to measure the morphological characteristics of porous materials. In the case of foams and granular media used for noise control applications, the most common of these characteristics are pore size and its distribution, porosity, and pore connectivity. In the case of fibrous media, the most useful non-acoustical characteristics are the fibre size and packing density. In the case of outdoor surfaces such as gravel, sandy soils, and agricultural land, which can be partly saturated with water, it is of direct interest to measure the degree of water saturation hydraulic permeability and pore size gradient. In the case of materials with good physiochemical properties, it is of interest to determine their internal pore surface area, porosity, and pore size scales. In this paper, the existing and newly emerging acoustic characterisation methods are discussed in terms of their complexity, accuracy, and sample requirements. The application of these methods relate to traditional needs to measure and predict the in-situ performance of noise control elements and outdoor surfaces, to ensure the quality control during material manufacturing process and to be able to measure non-invasively the micro-and nano-structure of porous media which is used in catalytic filters, electric capacitors and for gas storage. Parts of this paper were presented at the 22nd International Congress on Sound and Vibration in Florence.

Granuliuotų Medžiagų Garso Sugerties Prognozavimas Ir Vertinimas

“…Granuliuotos medžiagos, tokios kaip ir mineralinė vata ar akustiniai porolonai, yra laikomos porėtomis ir jų akustinę varžą ir galiausiai garso sugertį galima prognozuoti gerai žinomomis akustinių savybių modeliavimo formuluotėmis (Delany-Bazley ir Miki models) (Delany ir Bazley, 1970;Miki, 1990;Pfretzschner, 2002). Tačiau vėlesni autoriai pasiūlė naują formuluotę, kuria būtų įvertintas granuliuotų medžiagų porų pasiskirstymas (Horoshenkov ir Swift, 2002;Horoshenkov, 2017). Pasiūlytoje formuluotėje charakterizuojant granuliuotas medžiagas reikia įvertinti orinę varžą σ, poringumą φ, lenktumą (angl.…”

“…Skirtingos granuliuotos medžiagos dėl skirtingos granulių formos garsą sugeria skirtingai. Kadangi neįmanoma, kad granulės sugultų idealiai lygiai viena ant kitos per visą mėginio plotą, todėl orinė varža ir garso sugertis įvairiose mėginio ploto vietose bus skirtinga (Brzinski, Mayor ir Durian, 2013;Horoshenkov, 2017). Akustiniu požiūriu daug nagrinėtos yra gumos ir smėlio granulės (Sukontasukkul, 2009;Pfretzschner ir Rodriguez, 1999;Gayathri, Vasanthakumari ir Padmanabhan.…”

Using Ultrasonic Waves to Determine the Microstructure of Snow

“…Properties of specific porous materials can be determined from reflected or transmitted acoustic waves using a classical inverse scattering mathematical approach (Horoshenkov, 2017). For example, the interaction of sound energy with the ground is an important effect in understanding sound propagation in a natural setting, and is governed in part by the porous properties of the surface materials (Attenborough et al, 2011).…”

“…Standard acoustic analysis methods frequently depend on a rigid-porous theoretical treatment of the ground to interpret the results and derive porous medium parameters from the acoustic measurements. In the case of air-filled porous materials, the theory is considerably simplified by assuming that the solid frame is rigid (that is, without motion), an approach used for many applications, including the ground effect on outdoor sound propagation (e.g., Albert, 2001;Allard and Atalla, 2009;Attenborough et al, 2011;Horoshenkov, 2017). These analyses do not include vibration and seismic wave effects.…”

Inverse identification of a higher order viscous parameter of rigid porous media in the high frequency domain

“…is of prime importance, and its pursuit has met wide interest in the literature (for a review, see Refs. [5,6]).…”