A finite element model of perforated panel absorbers including viscothermal effects

Most of the analytical models devoted to determine the acoustic properties of a rigid perforated panel consider the acoustic impedance of a single hole and then use the porosity to determine the impedance for the whole panel. However, in the case of not homogeneous hole distribution or more complex configurations this approach is no longer valid. This work explores some of these limitations and proposes a finite element methodology that implements the linearized Navier Stokes equations in the frequency domain to analyse the acoustic performance under normal incidence of perforated panel absorbers. Some preliminary results for a homogenous perforated panel show that the sound absorption coefficient derived from the Maa analytical model does not match those from the simulations. These differences are mainly attributed to the finite geometry effect and to the spatial distribution of the perforations for the numerical case. In order to confirm these statements, the acoustic field in the vicinities of the perforations is analysed for a more complex configuration of perforated panel. Additionally, experimental studies are carried out in an impedance tube for the same configuration and then compared to previous methods. The proposed methodology is shown to be in better agreement with the laboratorial measurements than the analytical approach.

Cumulative auditory effects resulting from multiple exposure to intense acoustic stimulation.

Pt. 1. Deafening effects of noise on the cat -- Pt. 2. Histological effects of intense sound on the inner ear.

Hydroaccoustic pinging as a diver tool for underwater navigation in surveying Puget Sound Eelgrass (Zostera marina) densities

Senior thesis written for Oceanography 445

A misspelt youth: Spelling and orthographic learning in university students as a function of spelling-sound consistency

Pseudowords with inconsistent vs. consistent spellings (e.g., nurch, with rhyme neighbours search, lurch & perch, vs. mish, with neighbours dish, wish) were presented with definitions for naming either twice or 6 times. In an oral spelling test, there were main and interactive effects of consistency and the number of training trials on accuracy and main effects only on response latency, with the improvement in accuracy from 2 to 6 training trials greater for the more poorly learned inconsistent items. Of most interest, the smaller effect of training on accuracy in the consistent condition was reliable; contrary to the most obvious prediction of dual route spelling models that the sublexical procedure should produce correct spellings for consistent items early in training. In a second task students wrote spellings of multisyllabic words containing unstressed indeterminate (schwa) vowels. In their errors on the schwa vowel, students showed sensitivity to the most common spelling overall but also they were influenced by differences in schwa spellings in English words as a function of the number of syllables and schwa position. These results indicate that dual route models of spelling will need to accommodate the consistency of spellings within categories defined by lexical structure variables.

The effects of varying forms and degrees of government intervention upon the effective competitiveness of UK small businesses

This doctoral thesis responds to the need for greater understanding of small businesses and their inherent unique problem-types. Integral to the investigation is the theme that for governments to effectively influence small business, a sound understanding of the factors they are seeking to influence is essential. Moreover, the study, in its recognition of the many shortcomings in management research and, in particular that the research methods and approaches adopted often fail to give adequate understanding of issues under study, attempts to develop an innovative and creative research approach. The aim thus being to produce, not only advances in small business management knowledge from the standpoints of government policy makers and `lq recipient small business, but also insights into future potential research method for the continued development of that knowledge. The origins of the methodology lay in the non-acceptance of traditional philosophical positions in epistemology and ontology, with a philosophical standpoint of internal realism underpinning the research. Internal realism presents the basis for the potential co-existence of qualitative and quantitative research strategy and underlines the crucial contributory role of research method in provision of ultimate factual status of the assertions of research findings. The concept of epistemological bootstrapping is thus used to develop a `lq partial research framework to foothold case study research, thereby avoiding limitations of objectivism and brute inductivism. The major insights and issues highlighted by the `lq bootstrap, guide the researcher around the participant case studies. A novel attempt at contextualist (linked multi-level and processual) analysis was attempted in the major in-depth case study, with two further cases playing a support role and contributing to a balanced emphasis of empirical research within the context of time constraints inherent within part-time research.

Differing effects of two synthetic phonics programmes on early reading development

Background: Synthetic phonics is the widely accepted approach for teaching reading in English: children are taught to sound out the letters in a word then blend these sounds together. Aims: We compared the impact of two synthetic phonics programmes on early reading.SampleChildren received Letters and Sounds (L&S; 7 schools) which teaches multiple letter-sound mappings or Early Reading Research (ERR; 10 schools) which teaches only the most consistent mappings plus frequent words by sight.MethodWe measured phonological awareness (PA) and reading from school entry to the end of the second (all schools) or third school year (4 ERR, 3 L&S schools). Results: PA was significantly related to all reading measures for the whole sample. However, there was a closer relationship between PA and exception word reading for children receiving the L&S programme. The programmes were equally effective overall, but their impact on reading significantly interacted with school-entry PA: children with poor PA at school entry achieved higher reading attainments under ERR (significant group difference on exception word reading at the end of the first year), whereas children with good PA performed equally well under either programme. Conclusions: The more intensive phonics programme (L&S) heightened the association between PA and exception word reading. Although the programmes were equally effective for most children, results indicate potential benefits of ERR for children with poor PA. We suggest that phonics programmes could be simplified to teach only the most consistent mappings plus frequent words by sight.

Effects of phonetic/phonics instruction on reading pronunciation (French level I)

Pronunciation training has been traditionally viewed as of limited importance in a communicatively oriented foreign language curriculum (Pennington & Richards, 1986). Many language instructors seemingly deny the usefulness of phonetic training and rely on a listen-and-repeat method with the use of audiotapes (Bate, 1989; Callamand & Pedoya, 1984; Jones, 1997). Beginners in French classes face the challenge of mastering a complex sound and grapheme-phoneme correspondence system without the benefit of specific instruction. Their pronunciation errors develop mostly from bad habits while decoding from print to sound (Dansereau, 1995). ^ The purpose of this study was to investigate the effectiveness of basic phonetic/phonics instruction on reading pronunciation accuracy in a French I language course. ^ The sample consisted of two groups of French I students from Florida International University, who received the same instruction in French language and culture during the fall semester of 1999. Only the experimental group received additional phonetic/phonics training. ^ The instrument consisted of three recorded reading tasks: isolated familiar words, isolated unfamiliar words, and dialogue. Research questions were analyzed using a one-way multivariate analysis of variance. Significant differences were found between the two groups on scores for each of the three sections of the instrument, and on the total scores. These findings support the hypothesis of the study and reveal the effectiveness of phonetic/phonics training for beginners of French. ^ The findings imply that beginning language students should receive the minimum knowledge they need to master the French phoneme-grapheme (sound-spelling) system. ^

Structure-based modeling of head -related transfer functions towards interactive customization of binaural sound systems

One of the most popular techniques for creating spatialized virtual sounds is based on the use of Head-Related Transfer Functions (HRTFs). HRTFs are signal processing models that represent the modifications undergone by the acoustic signal as it travels from a sound source to each of the listener's eardrums. These modifications are due to the interaction of the acoustic waves with the listener's torso, shoulders, head and pinnae, or outer ears. As such, HRTFs are somewhat different for each listener. For a listener to perceive synthesized 3-D sound cues correctly, the synthesized cues must be similar to the listener's own HRTFs. ^ One can measure individual HRTFs using specialized recording systems, however, these systems are prohibitively expensive and restrict the portability of the 3-D sound system. HRTF-based systems also face several computational challenges. This dissertation presents an alternative method for the synthesis of binaural spatialized sounds. The sound entering the pinna undergoes several reflective, diffractive and resonant phenomena, which determine the HRTF. Using signal processing tools, such as Prony's signal modeling method, an appropriate set of time delays and a resonant frequency were used to approximate the measured Head-Related Impulse Responses (HRIRs). Statistical analysis was used to find out empirical equations describing how the reflections and resonances are determined by the shape and size of the pinna features obtained from 3D images of 15 experimental subjects modeled in the project. These equations were used to yield “Model HRTFs” that can create elevation effects. ^ Listening tests conducted on 10 subjects show that these model HRTFs are 5% more effective than generic HRTFs when it comes to localizing sounds in the frontal plane. The number of reversals (perception of sound source above the horizontal plane when actually it is below the plane and vice versa) was also reduced by 5.7%, showing the perceptual effectiveness of this approach. The model is simple, yet versatile because it relies on easy to measure parameters to create an individualized HRTF. This low-order parameterized model also reduces the computational and storage demands, while maintaining a sufficient number of perceptually relevant spectral cues. ^

New trends in health architecture for children and the effects of the built environment on young patients

The objective of this thesis was to investigate the effects of the built environment on the outcome of young patients. This investigation included recent innovations in children's hospitals that integrated both medical and architectural case studies as part of their design issues. In addition, the intervention responded to man-made conditions and natural elements of the site. The thesis project, a Children's Rehabilitation Hospital, is located at 1500 N.W. River Drive in Miami, Florida. The thesis intervention emerged from a site analysis that focused on the shifting of the urban grid, the variation in scale of the immediate context and the visual-physical connection to the river's edge. Furthermore, it addressed the issues of overnight accommodation for patient's families, as well as sound control through the use of specific materials in space enclosures and open courtyards. The key to the success of this intervention lies in the special attention given to the integration between nature and the built environment. Issues such as the incorporation of nature within a building through the use of vistas and the exploitation of natural light through windows and skylights, were pivotal in the creation of a pleasant environment for visitors, employees and young patients.

A Binaural Cochlear Implant Sound Coding Strategy Inspired by the Contralateral Medial Olivocochlear Reflex.

OBJECTIVES: In natural hearing, cochlear mechanical compression is dynamically adjusted via the efferent medial olivocochlear reflex (MOCR). These adjustments probably help understanding speech in noisy environments and are not available to the users of current cochlear implants (CIs). The aims of the present study are to: (1) present a binaural CI sound processing strategy inspired by the control of cochlear compression provided by the contralateral MOCR in natural hearing; and (2) assess the benefits of the new strategy for understanding speech presented in competition with steady noise with a speech-like spectrum in various spatial configurations of the speech and noise sources. DESIGN: Pairs of CI sound processors (one per ear) were constructed to mimic or not mimic the effects of the contralateral MOCR on compression. For the nonmimicking condition (standard strategy or STD), the two processors in a pair functioned similarly to standard clinical processors (i.e., with fixed back-end compression and independently of each other). When configured to mimic the effects of the MOCR (MOC strategy), the two processors communicated with each other and the amount of back-end compression in a given frequency channel of each processor in the pair decreased/increased dynamically (so that output levels dropped/increased) with increases/decreases in the output energy from the corresponding frequency channel in the contralateral processor. Speech reception thresholds in speech-shaped noise were measured for 3 bilateral CI users and 2 single-sided deaf unilateral CI users. Thresholds were compared for the STD and MOC strategies in unilateral and bilateral listening conditions and for three spatial configurations of the speech and noise sources in simulated free-field conditions: speech and noise sources colocated in front of the listener, speech on the left ear with noise in front of the listener, and speech on the left ear with noise on the right ear. In both bilateral and unilateral listening, the electrical stimulus delivered to the test ear(s) was always calculated as if the listeners were wearing bilateral processors. RESULTS: In both unilateral and bilateral listening conditions, mean speech reception thresholds were comparable with the two strategies for colocated speech and noise sources, but were at least 2 dB lower (better) with the MOC than with the STD strategy for spatially separated speech and noise sources. In unilateral listening conditions, mean thresholds improved with increasing the spatial separation between the speech and noise sources regardless of the strategy but the improvement was significantly greater with the MOC strategy. In bilateral listening conditions, thresholds improved significantly with increasing the speech-noise spatial separation only with the MOC strategy. CONCLUSIONS: The MOC strategy (1) significantly improved the intelligibility of speech presented in competition with a spatially separated noise source, both in unilateral and bilateral listening conditions; (2) produced significant spatial release from masking in bilateral listening conditions, something that did not occur with fixed compression; and (3) enhanced spatial release from masking in unilateral listening conditions. The MOC strategy as implemented here, or a modified version of it, may be usefully applied in CIs and in hearing aids.

High Pressure Speed of Sound and Related Thermodynamic Properties of 1-Alkyl-3-methylimidazolium Bis[(trifluoromethyl)sulfonyl]imides (from 1-Propyl- to 1-Hexyl-)

The knowledge of thermodynamic high-pressure speed of sound in ionic liquids (ILs) is a crucial way either to study the nature of the molecular interactions, structure and packing effects or to determine other key thermodynamic properties of ILs essential for their applications in any chemical and industrial processes. Herein, we report the speed of sound as a function temperature at pressures up to 101 MPa in four ultrapure ILs: 1-propyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, 1-pentyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, and 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, taking into consideration their relaxation behavior. Additionally, to further improve the reliability of the speed of sound results, the density, isentropic compressibility, and isobaric heat capacity as a function of temperature and pressure are calculated using an acoustic method.

Chemical and physical effects of ultrasound: sonoluminescence and materials

When a liquid is irradiated with ultrasound, acoustic cavitation (the formation, growth, and implosive collapse of bubbles in liquids irradiated with ultrasound) generally occurs. This is the phenomenon responsible for the driving of chemical reactions (sonochemistry) and the emission of light (sonoluminescence). The implosive collapse of bubbles in liquids results in an enormous concentration of sound energy into compressional heating of the bubble contents. Therefore, extreme chemical and physical conditions are generated during cavitation. The study of multibubble sonoluminescence (MBSL) and single-bubble sonoluminescence (SBSL) in exotic liquids such as sulfuric acid (H2SO4) and phosphoric acid (H3PO4) leads to useful information regarding the intracavity conditions during bubble collapse. Distinct sonoluminescing bubble populations were observed from the intense orange and blue-white emissions by doping H2SO4 and H3PO4 with sodium salts, which provides the first experimental evidence for the injected droplet model over the heated-shell model for cavitation. Effective emission temperatures measured based on excited OH• and PO• emission indicate that there is a temperature inhomogeneity during MBSL in 85% H3PO4. The formation of a temperature inhomogeneity is due to the existence of different cavitating bubble populations: asymmetric collapsing bubbles contain liquid droplets and spherical collapsing bubbles do not contain liquid droplets. Strong molecular emission from SBSL in 65% H3PO4 have been obtained and used as a spectroscopic probe to determine the cavitation temperatures. It is found that the intracavity temperatures are dependent on the applied acoustic pressures and the thermal conductivities of the dissolved noble gases. The chemical and physical effects of ultrasound can be used for materials synthesis. Highly reactive species, including HO2•, H•, and OH• (or R• after additives react with OH•), are formed during aqueous sonolysis as a consequence of the chemical effects of ultrasound. Reductive species can be applied to synthesis of water-soluble fluorescent silver nanoclusters in the presence of a suitable stabilizer or capping agent. The optical and fluorescent properties of the Ag nanoclusters can be easily controlled by the synthetic conditions such as the sonication time, the stoichiometry of the carboxylate groups to Ag+, and the polymer molecular weight. The chemical and physical effects of ultrasound can be combined to prepare polymer functionalized graphenes from graphites and a reactive solvent, styrene. The physical effects of ultrasound are used to exfoliate graphites to graphenes while the chemical effects of ultrasound are used to induce the polymerization of styrene which can then functionalize graphene sheets via radical coupling. The prepared polymer functionalized graphenes are highly stable in common organic solvents like THF, CHCl3, and DMF. Ultrasonic spray pyrolysis (USP) is used to prepare porous carbon spheres using energetic alkali propiolates as the carbon precursors. In this synthesis, metal salts are generated in situ, introducing porous structures into the carbon spheres. When different alkali salts or their mixtures are used as the precursor, carbon spheres with different morphologies and structures are obtained. The different precursor decomposition pathways are responsible for the observed structural difference. Such prepared carbon materials have high surface area and are thermally stable, making them potentially useful for catalytic supports, adsorbents, or for other applications by integrating other functional materials into their pores.

Limits to tDCS effects in language:failures to modulate word production in healthy participants with frontal or temporal tDCS

Transcranial direct current stimulation (tDCS) is a method of non-invasive brain stimulation widely used to modulate cognitive functions. Recent studies, however, suggests that effects are unreliable, small and often non-significant at least when stimulation is applied in a single session to healthy individuals. We examined the effects of frontal and temporal lobe anodal tDCS on naming and reading tasks and considered possible interactions with linguistic activation and selection mechanisms as well possible interactions with item difficulty and participant individual variability. Across four separate experiments (N, Exp 1A = 18; 1B = 20; 1C = 18; 2 = 17), we failed to find any difference between real and sham stimulation. Moreover, we found no evidence of significant effects limited to particular conditions (i.e., those requiring suppression of semantic interference), to a subset of participants or to longer RTs. Our findings sound a cautionary note on using tDCS as a means to modulate cognitive performance. Consistent effects of tDCS may be difficult to demonstrate in healthy participants in reading and naming tasks, and be limited to cases of pathological neurophysiology and/or to the use of learning paradigms.