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Thesis (Ph.D.), School of Mechanical and Materials Engineering, Washington State University ; Thermoacoustic phenomena in small-scale systems are investigated, and results are presented on the following topics: the acoustic properties of porous and fibrous materials, the modeling of thermoacoustic resonators with nonuniform medium and boundary conditions, and the harvesting of energy from tonal sound excited by heat addition and vortex shedding. The transfer function measurement system is used to find the acoustic properties of porous and fibrous materials. The complex wave numbers and characteristic impedances of reticulated vitreous carbon (RVC) and plastic mesh are determined using a variation of the three-microphone and four-microphone methods with the transfer function technique. The wave numbers and characteristic impedances of RVC and plastic mesh can be estimated from the obtained results. To find the effect of temperature difference, relative acoustic power changes across RVC, stacked plastic screens and stacked steel screens at ; Department of Mechanical Engineering, Washington State University

The present Paper aims to present a brief discourse on acoustic features related to human speech from the view point of analysis. After giving a brief review of modern methods currently in use in speech communication research, acoustic characteristics and features of human speech sound on the basis of spectrographic analysis of a limited number of Hindi Speech Sound are presented. The acoustic phonetic and the aeoustic prosodic parameters of human speech are briefly explained and the formant frequencies, and duration of Hindi vowels, concentration of acoustic energy for plosives and some affricates along with other related Parameters of conmsonants are presented in tabular form and discussed.

To meet the demands of a larger share of the electrical energy produced by intermittent renewable energy sources, an increasing amount of plannable energy sources is needed. One solution to handle this is to increase the amount of energy storage in the electrical grids. The most widespread energy storage technology today is by far pumped hydro storage (PHS). In an attempt to enable PHS at low-head sites, the ALPHEUS (augmenting grid stability through low head pumped hydro energy utilization and storage) EU Horizon 2020 research project was formed. In ALPHEUS, new axial flow, low-head, contra-rotating pump-turbine (CRPT) designs are investigated. A CRPT has two individual runners rotating in opposite directions. CRPTs developed within the ALPHEUS project have already been thoroughly analysed at stationary and transient operating conditions by the authors. However, the effects on the CPRT's performance due to potential cavitation on the runner blade surfaces have previously not been investigated. For that reason, the current study focuses on running cavitation simulations on a model scale CRPT using the OpenFOAM computational fluid dynamics (CFD) software. In the CFD simulations, cavitation is modelled as a two-phase liquid-vapour mixture using the interPhaseChangeDyMFoam solver. The two runner domains have a prescribed solid body rotation. Condensation and evaporation processes are handled with the Schnerr-Sauer model. Turbulence is managed with the k-omega shear stress transport-scale adaptive simulation (kOmegaSSTSAS) model. Flow-driving pressure differences over the computational domain are achieved with the headLossPressure boundary condition to emulate a larger experimental test facility of which the CRPT is part. Figure 1 shows a snapshot in time of an iso-surface (light blue) of cavitating cloud with alpha_liquid=0.9 in turbine mode. At this operating point, a small amount of cavitating flow is found by the suction side of the leading edges of the left runner, which is facing a lower reservoir. In Figure 2, the same type of iso-surface is shown, however now in pump mode. It is seen that the pump mode operating condition is much worse than the turbine mode. The cavitating cloud covers most of the suction side of the left runner, additionally, the tip-clearance region is also exposed to cavitation. Furthermore, traces of cavitation are found on the leading edges of the right runner as well as on the left small-support struts. It is thus important to, at least, analyse the pump mode to determine if and how much cavitation affects the CRPS's operating performance.

Thesis (Ph.D.)--University of Washington, 2013 ; In coastal environments, when topographic and bathymetric constrictions are combined with large tidal amplitudes, strong currents (> 2 m/s) can occur. Because such environments are relatively rare and difficult to study, until recently, they have received little attention from the scientific community. However, in recent years, interest in developing tidal hydrokinetic power projects in these environments has motivated studies to improve this understanding. In order to support an analysis of the acoustic effects of tidal power generation, a multi-year study was conducted at a proposed project site in Puget Sound (WA) are analyzed at a site where peak currents exceeded 3.5 m/s. From these analyses, three noise sources are shown to dominate the observed variability in ambient noise between 0.02-30 kHz: anthropogenic noise from vessel traffic, sediment-generated noise during periods of strong currents, and flow-noise resulting from turbulence advected over the hydrophones. To assess the contribution of vessel traffic noise, one calendar year of Automatic Identification System (AIS) ship-traffic data was paired with hydrophone recordings. The study region included inland waters of the Salish Sea within a 20 km radius of the hydrophone deployment site in northern Admiralty Inlet. The variability in spectra and hourly, daily, and monthly ambient noise statistics for unweighted broadband and M-weighted sound pressure levels is driven largely by vessel traffic. Within the one-year study period, at least one AIS transmitting vessel is present in the study area 90% of the time and over 1,363 unique vessels are recorded. A noise budget for vessels equipped with AIS transponders identifies cargo ships, tugs, and passenger vessels as the largest contributors to noise levels. A simple model to predict received levels at the site based on an incoherent summation of noise from different vessel types yields a cumulative probability density function of broadband sound pressure ...

The acoustic gas analyzer is an electro-acoustic type instrument which measures the velocity of sound in binary gas mixtures and translates this measurement into terms of mol faction of one component of the gas. It is most sensitive and accurate for gas pairs whose constituents have large differences in molecular weight. The measurement is independent of gas pressure. ; "Oak Ridge Gaseous Diffusion Plant operated by Union Carbide Nuclear Company, Division of Union Carbide Corporation for the Atomic Energy Commission acting under U.S. government contract W7405 eng 26." ; "Date of Issue: February 4, 1959 ; Report Number: K-1240 ; File Number: S-255; RES 1732 ; Subject Category: Instruments." ; Includes bibliographical references (p. 59). ; The acoustic gas analyzer is an electro-acoustic type instrument which measures the velocity of sound in binary gas mixtures and translates this measurement into terms of mol faction of one component of the gas. It is most sensitive and accurate for gas pairs whose constituents have large differences in molecular weight. The measurement is independent of gas pressure. ; Mode of access: Internet.

Accurate characterisation of fluid flow at tidal energy sites is critical for cost effective Tidal Energy Converter (TEC) design in terms of efficiency and survivability. The standard instrumentation in tidal site characterisation has been Diverging acoustic-Beam Doppler Profilers (DBDPs) which remotely measure the flow over a range of scales, resolving up to three velocity vectors. However, they are understood to have several drawbacks particularly in terms of characterising turbulent aspects of the flow. This characterisation is generally based upon a small number of key transient metrics, the accuracy of which directly impacts TEC designs. This work presents an optimisation and performance assessment of newly available Single Beam Doppler Profilers (SBDPs) mounted on a commercial-scale tidal turbine at mid-channel depth in a real operating environment. It was hypothesised that SBDPs would have advantages over DBDPs for site characterisation, in terms of reduced random error, reduced uncertainty in turbulence intensities and the ability to quantify the structure of the turbulent flow. The relationship between random error, sensor orientation and flow speed is quantified for both single and diverging beam sensor types. Random error was found to increase with increasing flow velocity as a power law, the slope of which varies for different sensor orientations. Quantification of noise offers a practical method to correct turbulence metrics. To enable the use of multiple acoustic sensors mounted in close proximity, interference was quantified and mitigation techniques examined. Cross-talk between sensors of the same type were generally shown to bias measurements towards zero. In the presence of alternate types of acoustic sensors, interference caused an increase in standard deviation of velocity results. Implementing a timing offset control mechanism was able to mitigate this effect. This work has achieved a greater understanding of the drivers (spatial separation, inclination angle, pulse power) and effects on ...

This paper presents the first acoustic experimental results of a MEMS based bulk piezoelectric transducer for use in fully implantable cochlear implants (FICI). For this purpose, the transducer was attached onto an acoustically vibrating membrane. Sensing and energy harvesting performances were measured using neural stimulation and rectifier circuits, respectively. The chip has a 150 Hz bandwidth around 1800 Hz resonance frequency that is suitable for mechanical filtering as a sensor. As an energy harvester, bulk piezoelectric transducer generated a rectified power of 16.25 μW with 2.47 VDC with 120 dB-A sound input at 1780 Hz. Among other MEMS acoustic energy harvesters in the literature, reported transducer has the highest power density (1.5 × 10−3 W/cm3) to our knowledge.

Eight small wind turbines ranging from 400 watts to 100 kW in rated power were tested for acoustic emissions at the U.S. Department of Energy's National Renewable Energy Laboratory. Rigorous test procedures based on international standards were followed for measurements and data analyses. Results are presented in the form of sound pressure level versus wind speed, where the sound was recorded downwind of the turbine at a distance equal to the hub height plus half the rotor diameter. When there was sufficient separation between wind turbine noise and background noise, the apparent sound power level was calculated. In several cases, this was not possible. The implications of this problem are discussed briefly. Some of the configurations tested were specifically developed to reduce the noise level of their predecessors. Test data for these machines demonstrate marked progress toward quieter turbines.

The present work is about an acoustic design for a former church converted into a multi-purpose auditorium. The current status of the hall has been classified by means of an acoustic measurements campaign complying with technical standards requirements. A numerical model, which has been calibrated through the measured values, led to the development of the acoustic design that includes sustainable and not-invasive interventions. In contrast with the practical habits, which would use a large amount of sound absorbing materials, an array of suspended reflecting panels over the musicians positions has been introduced. Exploiting the reflecting and scattering properties of those objects, sound clarity and speech definition improve. All the treatments are validated using numerical simulation softwares in order to estimate the efficiency of the whole improvement proposal. IN_BO. Ricerche e progetti per il territorio, la città e l'architettura, V. 8, N. 11 (2017): IL FUTURO DEGLI EDIFICI DI CULTO: PAESAGGI. A cura di Luigi Bartolomei

International audience The vibrational conductivity approach is sometimes used to evaluate the spatial repartition of the energy density of dynamical structural/acoustic systems in high frequency range. This is a significant improvement of the Statistical Energy Analysis which only provides a single energy value per sub-system. However, this model is based on the underlying assumption that the wave field is constructed as a superposition of plane waves. This hypothesis may fail for largely non diffuse fields. This paper is devoted to the study of other types of waves. The fields are still described in terms of energy quantities which are solved using a differential equation written along the "streamlines of energy". Results strongly depend on the geometry of these streamlines. Whenever this geometry is known, for instance for plane, cylindrical and spherical waves, the differential equation may be solved. The plane wave case is in good agreement with the vibrational conductivity approach, whereas a large class of other waves are generated by this equation. Some numerical simulations illustrate these facts.