The coupling of a hearing aid loudspeaker membrane to visco-thermal air layers

Hearing aids and their components are becoming smaller. This presents new problems for the acoustical components, such as the loudspeaker. A circular membrane of a hearing aid loudspeaker is modeled in this paper. Neglecting air influences, the membrane and its suspension behave as a mass spring system. However, under operating conditions, thin layers of air on both sides of the membrane influence its behavior. Air can enter and leave these layers at certain locations on the circular edge of the layer. Since these air layers are thin, visco-thermal effects may have to be taken into account. Therefore, the air layers are not modeled by the wave equation, but by the low reduced frequency model that takes these visco-thermal effects into account. The equations of this model are solved in a polar coordinate system, using a wave-based method. The other acoustical parts of the hearing aid loudspeaker, and the membrane itself are modeled by simple lumped models. The emphasis in this paper is on the coupling of the viscothermal air layer model to the mechanical model of the membrane. Coupling of the air layer to other acoustical parts by using an impedance as boundary condition for the layer model, is also described. The resulting model is verified by experiments. The model and the measurements match reasonably well, considering the level of approximation with lumped parts

Sound radiation from a buried nozzle with jet and bypass flow

Abstract Radiation of sound from a simplified model of a buried nozzle with bypass flow is studied. More precisely, a semi-infinite duct (the inner nozzle) is situated inside a larger semi-infinite duct. The exit plane of the larger duct either coincides with the exit plane of the smaller duct, or extends beyond it. Differences in the piece-wise subsonic mean flow velocity, density and temperature are taken into account. The inner nozzle issues the core flow inside the bypass jet flow. The bypass nozzle issues the bypass jet flow inside the ambient co-flow. Two vortex sheets, attached to the duct exits, separate the different flows from each other. These vortex sheets are unstable due to this mean velocity discontinuity. The application of the Kutta condition at the respective trailing edges guarantees shedding of vorticity which excites these instabilities. The system is set up to respond to an incident annular duct mode, but the analysis would be very similar for an inner duct mode. To obtain an analytical solution a Wiener-Hopf approach with Idemen's method of "weak factorisation" is applied. Formulation of the boundary value problem following the classical approach leads to a couple of simultaneous Wiener-Hopf equations. These equations produce a matrix equation system, which is formally decoupled by the introduction of an infinite sum of poles with coefficients to be determined. The uncoupled scalar equations are solved independently by a standard application of analytical continuation. The unknown coefficients in the final solution are determined by solving an infinite linear algebraic system numerically. The contribution of the instability waves are separated from the rest of the solution. The asymptotic far field is found by a standard application of the steepest descent method. Finally a series of practical examples are given

An analysis of potential barriers and enablers to regulating the television marketing of unhealthy foods to children at the state government level in Australia

Background In Australia there have been many calls for government action to halt the effects of unhealthy food marketing on children\u27s health, yet implementation has not occurred. The attitudes of those involved in the policy-making process towards regulatory intervention governing unhealthy food marketing are not well understood. The objective of this research was to understand the perceptions of senior representatives from Australian state and territory governments, statutory authorities and non-government organisations regarding the feasibility of state-level government regulation of television marketing of unhealthy food to children in Australia.Method Data from in-depth semi-structured interviews with senior representatives from state and territory government departments, statutory authorities and non-government organisations (n=22) were analysed to determine participants\u27 views about regulation of television marketing of unhealthy food to children at the state government level. Data were analysed using content and thematic analyses.Results Regulation of television marketing of unhealthy food to children was supported as a strategy for obesity prevention. Barriers to implementing regulation at the state level were: the perception that regulation of television advertising is a Commonwealth, not state/territory, responsibility; the power of the food industry and; the need for clear evidence that demonstrates the effectiveness of regulation. Evidence of community support for regulation was also cited as an important factor in determining feasibility.Conclusions The regulation of unhealthy food marketing to children is perceived to be a feasible strategy for obesity prevention however barriers to implementation at the state level exist. Those involved in state-level policy making generally indicated a preference for Commonwealth-led regulation. This research suggests that implementation of regulation of the television marketing of unhealthy food to children should ideally occur under the direction of the Commonwealth government. However, given that regulation is technically feasible at the state level, in the absence of Commonwealth action, states/territories could act independently. The relevance of our findings is likely to extend beyond Australia as unhealthy food marketing to children is a global issue.<br /

Oxygen saturation and outcomes in preterm infants

BACKGROUN

Emerging technologies for the production of renewable liquid transport fuels from biomass sources enriched in plant cell walls

Plant cell walls are composed predominantly of cellulose, a range of non-cellulosic polysaccharides and lignin. The walls account for a large proportion not only of crop residues such as wheat straw and sugarcane bagasse, but also of residues of the timber industry and specialist grasses and other plants being grown specifically for biofuel production. The polysaccharide components of plant cell walls have long been recognized as an extraordinarily large source of fermentable sugars that might be used for the production of bioethanol and other renewable liquid transport fuels. Estimates place annual plant cellulose production from captured light energy in the order of hundreds of billions of tons. Lignin is synthesized in the same order of magnitude and, as a very large polymer of phenylpropanoid residues, lignin is also an abundant, high energy macromolecule. However, one of the major functions of these cell wall constituents in plants is to provide the extreme tensile and compressive strengths that enable plants to resist the forces of gravity and a broad range of other mechanical forces. Over millions of years these wall constituents have evolved under natural selection to generate extremely tough and resilient biomaterials. The rapid degradation of these tough cell wall composites to fermentable sugars is therefore a difficult task and has significantly slowed the development of a viable lignocellulose-based biofuels industry. However, good progress has been made in overcoming this so-called recalcitrance of lignocellulosic feedstocks for the biofuels industry, through modifications to the lignocellulose itself, innovative pre-treatments of the biomass, improved enzymes and the development of superior yeasts and other microorganisms for the fermentation process. Nevertheless, it has been argued that bioethanol might not be the best or only biofuel that can be generated from lignocellulosic biomass sources and that hydrocarbons with intrinsically higher energy densities might be produced using emerging and continuous flow systems that are capable of converting a broad range of plant and other biomasses to bio-oils through so-called 'agnostic' technologies such as hydrothermal liquefaction. Continued attention to regulatory frameworks and ongoing government support will be required for the next phase of development of internationally viable biofuels industries.Hwei-Ting Tan, Kendall R. Corbin and Geoffrey B. Finche

Outcomes of Two Trials of Oxygen-Saturation Targets in Preterm Infants

BACKGROUN

ICSV14 THE EFFECTS OF LOW-FREQUENCY VIBRATIONS ON CONTROL PROFILE OF BLOOD

Abstract Vibrating platforms are widely employed in sport facilities and fitness clubs to help people develop muscles and improve their physical condition. The applied vibration frequencies ranged from 30 to 60 Hz and vibration&apos;s amplitudes were regarded as &quot;considerable&quot;. There are few reports in literature on the potential applications of low-frequency vibrations in therapy (e.g. Military Hospital in Busko, Poland. Therefore, a research program was undertaken at the AGH University of Science and Technology to investigate the effects of low-frequency vibration on selected parameters of control profile (urea, creatine, bilirubin, transaminase ALT, transaminase AST, alkaline phosphatase, albumin, total protein, calcium, phosphorus) of human blood. Cyclic fluctuations of bone loading were induced by the applied harmonic vibration 3.5 Hz and amplitude 4 mm. The experiments utilising two vibrating platforms were performed in the Laboratory of Structural Acoustics and Biomedical Engineering AGH-UST. The applied vibrations were harmless and not annoying, in accordance with the standard PN-EN ISO 130901-1, 1998. 28 women volunteers had 19 sessions on subsequent working days, at the same time of day. During the tests the participants remained passive, in the standing position. This paper is the continuation of the study covering the effects of low-frequency vibrations on selected physiological parameters of the human body. The experiments were conducted to find to answer whether vibration&apos;s exposure (total duration of training sessions 6 hours 20 min) should produce any changes in control profile of blood. Research data showed that low-frequency vibrations can be treated as isometric physical training and might be well applied to support the therapy of numerous civilisation-related diseases, such as: overweight, hypertension, osteoporosis and anaemia. Research data also reveal a statistically significant decrease of phosphorus, total protein and bilirubin levels in blood serum

LOUD: A 1020-NODE MICROPHONE ARRAY AND ACOUSTIC

Recording speech and other sound is difficult in environments with a large amount of noise and/or crosstalk. In these environments, array microphones are needed in order to obtain a clean recording of desired speech. In this work, we have designed, implemented, and tested LOUD, a 1020-node microphone array. To the best of our knowledge and as documented by Guinness World Records [6], this is currently the largest microphone array in the world. We have implemented an acoustic beamforming algorithm for sound source amplification in a noisy environment, and have obtained preliminary results demonstrating the efficacy of the array. From one to 1020 microphones, we have shown a 13.7dB increase in peak SNR for a representative utterance, an 87.2 % drop in word error rate (WER) with interferer present, and an 91.3 % drop in WER without an interferer. 1

ICSV14 EXTENDING THE USABILITY OF NEAR-FIELD ACOUSTIC HOLOGRAPHY AND BEAMFORMING BY USING FOCALIZATION

Abstract In view of source localization techniques, two methods, Near-Field Acoustic Holography (NAH) and Beamforming, are widely used and well-known techniques. Both techniques have their advantages and disadvantages. Near-field Acoustic holography, the oldest commercially available method, has as major advantage its spatial resolution being equal to the microphone spacing and independent of frequency. This makes it a very powerful technique for low frequency problems. However when trying to analyse higher frequencies, the method becomes very tedious from a measurement standpoint. Beamforming, a far-field technique, has as major advantage that with a limited amount of measurement channels a relative large frequency range can be analysed, making the measurement sequence very simple. On the other hand, Beamforming has as disadvantage that its spatial resolution is proportional to the wavelength making the method not really useful for frequencies under 2000 Hz. In this paper, a technique called focalisation is discussed which can ameliorate the shortcomings from NAH and Beamforming. Focalisation is a near-field beamforming technique that can be used on data taken for NAH to extend the frequency range and double the usable frequency range for the same microphone spacing. In case of beamforming the same array can be used to take data in the near-field. When using focalisation in this near-field data, the spatial resolution is improved by a factor of 2. In addition, the focalisation allows calculating the sound power which is not possible with beamforming