O. Umnova

O. Umnova
University of Salford · Acoustics Research Centre

PhD

About

114
Publications
33,368
Reads
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1,371
Citations
Introduction
Additional affiliations
October 2004 - present
University of Salford
Position
  • Researcher in Acoustics

Publications

Publications (114)
Book
This book delivers a comprehensive and up-to-date treatment of practical applications of metamaterials, structured media, and conventional porous materials. With increasing levels of urbanization, a growing demand for motorized transport, and inefficient urban planning, environmental noise exposure is rapidly becoming a pressing societal and health...
Article
Full-text available
Acoustic metamaterial absorbers have been built and tested with focus on low frequency airborne sound absorption in linear and nonlinear regimes. The absorbers are made up of a series of piled up flat cavities, separated by thin walls and traversed by a perforation at their centre. A model for absorber effective properties is developed and compared...
Article
The nonlinear dynamics of coupled waves in one-dimensional granular chains with and without a substrate is theoretically studied accounting for quadratic nonlinearity. The multiple time scale method is used to derive the nonlinear dispersion relations for infinite granular chains and to obtain the wave solutions for semi-infinite systems. It is sho...
Article
This paper introduces a model for the propagation of multiple types of waves in a compressed granular chain placed on an elastic V-shaped rail. The system possesses translational, rotational, and torsional degrees of freedom, and the different waves interact due to the presence of Hertzian contacts between adjacent spheres and between the spheres a...
Poster
Full-text available
Popular empirical models developed for the characterization of sound absorbing materials such as foams, felts and fabrics have been reviewed. Two varieties of polyester based fabrics have been studied in this work. Initially the best fit model for flow resistivity has been identified, followed by obtaining sound absorption characteristics. Results...
Article
Full-text available
Osteoporosis is an asymptomatic bone condition that affects a large proportion of the elderly population around the world, resulting in increased bone fragility and increased risk of fracture. Previous studies had shown that the vibroacoustic response of bone can indicate the quality of the bone condition. Therefore, the aim of the authors’ project...
Conference Paper
Osteoporosis is a prevalent but asymptomatic condition that affects a large population of the elderly, resulting in a high risk of fracture. Several methods have been developed and are available in general hospitals to indirectly assess the bone quality in terms of mineral material level and porosity. In this paper we describe a new method that use...
Conference Paper
Full-text available
To keep up with the stringent norms and regulations, a lot of research has been put into the design and development of quieter moving parts and spaces, popularly involving improvisation in the technology of ducts and silencers. Prominent theoretical research based on the Acoustic Black Hole (ABH) effect has been developed that focuses on achieving...
Poster
Full-text available
In this study, the nonwoven samples have been characterised for determining their potentiality as acoustic absorbents. Effective properties such as the fabric density have been parametrised to understand its impact on the sound reflection and absorption characteristics. Experimental analyses has been carried out using the Impedance Tube test for a...
Article
The acoustic properties of an air-saturated porous material depend on its microstructure and the thickness of the sample. Thick samples of conventional acoustic materials are required to achieve good absorption at low frequencies. This study suggests a new micro-structure for the design of low-frequency resonant acoustic absorbers. A perforated mat...
Conference Paper
Full-text available
Sub-wavelength absorbers based on the Acoustic Black Hole (ABH) effect are being currently researched upon both numerically (O. Guasch, et. al., 2017) and experimentally (A. El-Ouahabi, et. al., 2015). Theoretically, they have been derived to achieve total absorption of sound (M. A. Mironov and V. V. Pislyakov, 2002), thus representing an ideal ABH...
Article
Full-text available
The propagation of long-wavelength sound in the presence of a metasurface made by arranging acoustic resonators periodically upon or slightly above an impervious substrate is studied. The method of two-scale asymptotic homogenization is used to derive effective boundary conditions, which account for both the surface corrugation and the low-frequenc...
Article
Full-text available
This paper investigates sound propagation in multiscale rigid-frame porous materials that support mass transfer processes, such as sorption and different types of diffusion, in addition to the usual visco-thermo-inertial interactions. The two-scale asymptotic method of homogenization for periodic media is successively used to derive the macroscopic...
Conference Paper
Full-text available
Acoustic metamaterials have been under extensive study to understand structural responses to sound waves. Owing to the distinguishing capability of manipulating sound waves, a broad range of applications have been realized for these materials. One such application has been to enhance the potentiality of existing sound absorbing devices. Sub-wavelen...
Conference Paper
Full-text available
It was shown recently in Nevers, France, Sherbrooke, Canada and Salford, UK, that porous materials with semi-opened pores or materials with open pores bearing lateral cavities or resonators at the microscopic scale of the pores can result in peculiar sound absorption properties. Various examples of these materials can be found in engineering and in...
Conference Paper
Full-text available
This paper investigates sound propagation in multiscale sorptive porous materials saturated with a pure gas. An example of this type of materials is a packing of porous grains where a mesoscopic, microscopic, and nanoscopic scale can be identified. These scales are associated with the grain size, and the micrometric and nanometric pores inside the...
Article
This presentation examines a perforated resonant material, in which the principal perforations comprise a network of periodically spaced dead-end pores. This material can show good sound absorption at low frequencies, particularly given its relatively small thickness. In a recent study, this kind of material was modeled by an effective fluid approa...
Article
This work continues a series of studies on the link between the microstructure of multiscale materials and their acoustical properties [1]-[3]. Granular activated carbons are excellent low frequency sound absorbers. Two factors contribute to this. (i) They have three scales of heterogeneities: millimetric grains and micrometric and nanometric inner...
Article
Efficient manipulation of sound waves by some resonant acoustic metasurface designs has recently been reported in the literature. This paper presents a general theoretical framework for the description of sound wave interaction with the resonant metasurface that is independent of the nature of resonators and the excitation. The equations governing...
Conference Paper
Full-text available
Acoustic Black Holes (ABH) have been a topic of intensive research in the last decade. These structures are based on the principle of impedance matching and, in principle, can achieve a total absorption of incident sound. Until now, a majority of ABH, have been considered for shear waves or Rayleigh - Lamb waves travelling over surfaces such as pla...
Article
Full-text available
Granular activated carbon (GAC) has numerous applications due to its ability to adsorb and desorb gas molecules. Recently, it has been shown to exhibit unusually high low frequency sound absorption. This behavior is determined by both the multi-scale nature of the material, i.e., the existence of three scales of heterogeneities, and physical proces...
Article
Full-text available
The acoustical and related non-acoustical properties of activated carbon were studied to understand better the effect of added catalyst and acid treatment on the nano- and micro-structure of activated, porous nano-carbon. The acoustical impedance was measured in a 45 mm diameter impedance tube with a special adaptor to accommodate a very small mate...
Conference Paper
Full-text available
A theoretical and numerical study of the sound propagation in air-saturated porous media with straight pores bearing lateral cavities (dead-ends) is proposed. The straight pores can be considered as the main (Biot) pores. The lateral cavities are located at " nodes " periodically spaced along each " main pore " axis. The effect of periodicity in th...
Article
Full-text available
A theoretical and numerical study of the sound propagation in air-saturated porous media with straight main pores bearing lateral cavities (dead-ends) is presented. The lateral cavities are located at "nodes" periodically spaced along each main pore. The effect of periodicity in the distribution of the lateral cavities is studied, and the low frequ...
Conference Paper
Full-text available
RESUMEN: Metamateriales acústicos son materiales fabricados artificialmente, los cuales están diseñados con el fin de controlar, direccionar y manipular ondas sonoras. Estos materiales están adquiriendo bastante popularidad debido a que presentan propiedades acústicas que no son comúnmente observadas en materiales convencionales. Entre éstas, se en...
Conference Paper
The interactions between acoustic waves and an array of resonators are studied. The resonators are arranged periodically on an impedance surface so that the scale separation between sound wavelength and the array period is achieved. An asymptotic multi-scale model which accounts for viscous and thermal losses in the resonators is developed and is u...
Article
Periodic arrays of slotted cylinders have been studied with a focus on analytical and semi-analytical techniques, observing near-field interactions and their influence on reflection and transmission of acoustic waves by the array. Relative orientation of the cylinders within a unit cell has been shown to strongly affect the array behavior, facilita...
Article
Air saturated porous materials, namely, foams and wools, are often used as sound absorbing materials. Nevertheless, they suffer from a lack of absorption efficiency at low frequencies, which is inherent to their absorption mechanisms (viscous and thermal losses), even when used as optimized multilayer or graded porous materials. These last decades,...
Article
Full-text available
An omnidirectional sound absorber based on the acoustic analogy of the electromagnetic metamaterial “black hole” has been developed and tested. The resulting structure is composed of a hollow cylindrical porous absorbing core and a graded index matching layer which employs multiple rods of varying size and spacing to gradually adjust the impedance...
Data
Full-text available
It has been shown in the earlier work of Umnova et al. [Noise Control Eng. 50, 204–210 (2002)] that interaction of a relatively long, high amplitude acoustic pulse with a rigid porous material can be accurately described accounting for the Forchheimer nonlinearity. In the present study, the goal is to determine whether the accuracy of the modeling...
Data
Full-text available
It has been shown in the earlier work of Umnova et al. [Noise Control Eng. 50, 204–210 (2002)] that interaction of a relatively long, high amplitude acoustic pulse with a rigid porous material can be accurately described accounting for the Forchheimer nonlinearity. In the present study, the goal is to determine whether the accuracy of the modeling...
Article
Full-text available
The aim of this work is to design a layer of porous material with a high value of the absorption coefficient in a wide range of frequencies. It is shown that low frequency performance can be significantly improved by embedding periodically arranged resonant inclusions (slotted cylinders) into the porous matrix. The dissipation of the acoustic energ...
Article
Full-text available
Two effective medium models are presented and used to predict complex reflection and transmission coefficients of finite periodic arrays of resonant elastic shells as well as their effective density and bulk modulus at low frequencies. Comparisons with full multiple scattering theory and measurements show that the self-consistent model fails to cor...
Article
Full-text available
An omni-directional acoustic absorber consisting of a porous core and the impedance matching metamaterial layer has been designed and tested in the laboratory. Semi-analytical and numerical models have been developed and validated. The numerical model takes into account the viscous losses in the matching layer. A 1.5 m demonstrator has been built a...
Article
Full-text available
This paper presents and compares three analytical methods for calculating low frequency band gap boundaries in doubly periodic arrays of resonating thin elastic shells. It is shown that both Foldy-type equations (derived with lattice sum expansions in the vicinity of its poles) and a self-consistent scheme could be used to predict boundaries of low...
Article
Full-text available
Activated carbon can adsorb and desorb gas molecules onto and off its surface. Research has examined whether this sorption affects low frequency sound waves, with pressures typical of audible sound, interacting with granular activated carbon. Impedance tube measurements were undertaken examining the resonant frequencies of Helmholtz resonators with...
Article
Full-text available
Mathematical methods are important for research in many aspects of acoustics. Most researchers in acoustics in the United Kingdom do not have access to master level courses to broaden their postgraduate study, so they advance their fundamental mathematical methodologies taught at undergraduate level through independent learning. They develop their...
Conference Paper
Full-text available
Granular materials have been conventionally used for acoustic treatment due to their sound absorptive and sound insulating properties. An emerging field is the study of the acoustical properties of double porosity materials. An example of these is a granular material in which the particles are porous. In this paper, analytical and hybrid analytical...
Article
Full-text available
The acoustical performances of regular arrays of cylindrical elements, with their axes aligned and parallel to a ground plane, have been investigated through predictions and laboratory experiments. Semi-analytical predictions based on multiple scattering theory and numerical simulations based on a boundary element formulation have been made. Measur...
Article
Full-text available
Granular materials have been conventionally used for acoustic treatment due to their sound absorptive and sound insulating properties. An emerging field is the study of the acoustical properties of multiscale porous materials. An example of these is a granular material in which the particles are porous. In this paper, analytical and hybrid analytic...
Article
An acoustic metamaterial made of a two-dimensional (2D) periodic array of multi-resonant acoustic scatterers is analysed in this paper. The building blocks consist of a combination of elastic beams of Low-Density Polyethylene Foam (LDPF) with cavities of known volume. Sound inside the structure can excite elastic resonances of the material as well...
Article
Full-text available
Scattering by (a) a single composite scatterer consisting of a concentric arrangement of an outer N-slit rigid cylinder and an inner cylinder which is either rigid or in the form of a thin elastic shell and (b) by a finite periodic array of these scatterers in air has been investigated analytically and through laboratory experiments. The composite...
Article
Full-text available
Analytical and numerical approaches have been made to the problems of (a) propagation through a doubly periodic array of elastic shells in air, (b) scattering by a single elastic shell in air, and (c) scattering by a finite periodic array of elastic shells in air. Using the Rayleigh identity and the Kirchhoff-Love approximations, a relationship is...
Conference Paper
Full-text available
Granular materials have been conventionally used for acoustic treatment due to their sound absorptive and sound insulating characteristics. An emerging field is the study of acoustical properties of multi-scale porous materials. An example of these is a double-porosity granular material in which the grains are porous themselves. In this work, a com...
Article
Full-text available
Most conventional diffusers take the form of a surface based treatment, and as a result can only operate in hemispherical space. Placing a diffuser in the volume of a room might provide greater efficiency by allowing scattering into the whole space. A periodic cylinder array (or sonic crystal) produces periodicity lobes and uneven scattering. Intro...
Article
Full-text available
Highly densified TiC, ZrC and HfC based ultrahigh temperature heteromodulus ceramics (HMC), containing 10?50?vol.?% of low modulus phase in the form of particulate graphite, were prepared by hot pressing at 2700?C and 12?MPa in argon atmosphere. The microstructure, elastic characteristics, flexural and compressive static strength, fracture toughnes...
Conference Paper
Full-text available
Plenary Lecture given at XIII Encuentro Internacional de Acústica SEMACUS 2010, 1-2 October, Santiago, Chile, 2010. Historical review of the theory of acoustics of porous media.
Conference Paper
Full-text available
Plenary lecture on sound propagation in multiscale porous materials given at XIII Encuentro Internacional de Acústica SEMACUS 2010, 1-2 October, Santiago, Chile.
Article
Periodic arrays of resonant scatterers can support low-frequency band gaps in addition to those associated with array periodicity. In the finite periodic arrays they correspond to frequency intervals of low transmission and lead to an improved attenuation below the first Bragg band gap. To describe low-frequency behavior, the effective medium model...
Article
Full-text available
An extended formulation of the relaxational model proposed by Wilson et al. in 1993 is presented in this paper. The proposed semi-empirical models for complex tortuosity and compressibility functions satisfy physically correct low and high frequency limits and allow analytical transformation into the time domain. These models are based on the assum...
Article
High-amplitude pulse propagation in rigid porous media has been investigated numerically and experimentally. At high-sound levels, strong interactions between different spectral components of the pulse make any frequency domain models difficult to use, therefore a time domain approach has been applied for the present research. The effect of Forchhe...
Article
The performance of a sonic crystal is characterized by the so-called Bragg band gaps where its insertion loss is very high. This effect makes sonic crystals effective noise barriers in the particular frequency intervals. However the presence of boundaries in the acoustic environment can have a great impact on the sonic crystal spectral properties....
Article
The main spectral property of a Sonic Crystal structure is notable sound attenuation related to the so-called Bragg band gaps. This effect makes Sonic Crystals effective noise barriers in a particular frequency range. This performance can be extended to a wider frequency interval by introducing scatterers supporting multiple resonances of various t...
Conference Paper
Full-text available
Most conventional diffusers take the form of a surface based treatment, and as a result can only operate in hemispherical space. By placing a diffuser in the volume of a room, scattering into the whole space becomes possible, receiving from and scattering into all possible directions. This affords potential for greater efficiency. One candidate str...
Conference Paper
Full-text available
The packing of porous particles is a classical example of a double porosity material. Their acoustical properties are strongly affected by the complexity of the inner structure. The small size of the pores together with large internal surface area means that diffusion and viscous flow have to be considered simultaneously in the derivation of the ef...
Article
Full-text available
A variety of new porous materials with unusually small pores have been manufactured in the past decades. To predict their acoustical properties, the conventional models need to be modified. When pore size becomes comparable to the molecular mean free path of a saturating fluid, the no-slip conditions on the pore surface are no longer accurate and h...
Article
Full-text available
A set of equations has been derived which corresponds to the time domain formulation of the equivalent fluid model. It models the propagation of an acoustic pulse in rigid frame porous material accounting for both viscous and thermal effects. It has been shown analytically and confirmed numerically that the equations can be reduced to those publish...