Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 49 for “"Sound Power"”.
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Sound power measurement in a semi-confined space,
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1971.
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The uncertainty in standardised sound power measurements: complying with ISO 17025
… of view, for a testing laboratory performing sound power measurement according to specific ISO standards and European Directives, the measurement of uncertainties is the most important factor to deal with. Sound power level measurement, according to ISO 3744:1994 , performed with a limited …
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Sound Absorption and Sound Power Measurements in Reverberation Chambers Using Energy Density Methods
… spatially averaged squared pressure to calculate sound absorption, sound power, and other sound measurements. While a reverberation chamber provides an approximation of a diffuse sound field, variations in the measurements introduce uncertainty in measurement results. Room qualification procedures …
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Application of cepstral techniques to the automated determination of the sound power absorption coefficient
… an apparatus that can rapidly determine the sound power absorption coefficient by a non-skilled operator in a noisy environment. The results should correlate closely with the standardised impedance tube method, within 0.05 over the range 200 Hz to 2000 Hz. The constraint that the apparatus be …
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Application of cepstrum techniques and a guard tube to the measurement of the normal incident sound power absorption coefficient of road surfaces in-situ
… an apparatus that was to measure the plane wave sound power absorption coefficient of road surfaces in-situ. Road traffic noise has been identified as the greatest noise pollutant in the industrialised world with the tyre/road interaction being the major source of noise for traffic speeds in …
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A turbulent combustion noise model
… model predicts (1) the pressure time series, (2) Sound Pressure Level (SPL) spectrum, (3) Over-All Sound Pressure Level (OASPL), (4) the thermoacoustic efficiency, (5) the peak frequency, and (6) the sound power of combustion generated noise. In addition, a correlation for sound power is developed …
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Uncertainty Quantification in Dynamic Problems With Large Uncertainties
… (AMV) method is used to calculate probabilistic sound power and the sensitivity of elastically supported panels with small uncertainty (coefficient of variation). Sound power calculations are done using Finite Element Method (FEM) and Boundary Element Method (BEM). The sensitivities of the sound …
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A Study of Distributed Active Vibration Absorbers (DAVA)
… frequency (< 1000 Hz) mean square velocity and sound power radiation. A numerical model of a multi-DAVA system was developed using the Rayleigh-Ritz method coupled to a hierarchical finite element set (p-method). The numerical model was validated and used to optimize DAVA configurations using …
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Acoustic Characterization and Preliminary Noise Control of Pneumatic Percussion Tools
… determine the spectral characteristics, overall sound power level, and spatial source strength maps of the tool. A spherical array of microphones was used to obtain an accurate estimate of the overall sound power levels and the directivity. The overall sound power radiation was found to be in the …
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Power efficiency analysis for an Active structure
Methods for analyzing the structural-acoustic power efficiency of active structures are developed. For this work we define the power efficiency as the ratio of the sound power radiated by a structure to the maximum possible radiated sound power. An active structure is defined as one that has …
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Vibrations of and sound radiation from some periodic structures under convected loadings
… shells excited by random convected loadings. The sound power radiated under these conditions is also dealt with. The stiffened structures are represented by uniform beams, plates or shells on periodically spaced elastic supports which represent stiffener-skin interaction forces and moments. The …
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Error Sensor Placement for Active Control of an Axial Cooling Fan
… to a theoretical condition of minimized sound power. A theoretical point source model, based on the condition previously stated, reveals the location of near-field pressure nulls that may be used to optimize error sensor placement. The actual locations of these near-field pressure nulls …
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Control of Sound Radiation From Structures with Periodic Smart Skins
… skin concept for the reduction of the radiated sound power from a vibrating structure is proposed. The skin has a periodic structure and continuously covers a vibrating beam. Thus, this skin decouples the vibrating structure from the acoustic field by modifying the wavenumber spectrum of the …
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Attenuation of Low Frequency Structurally Radiated Noise With an Array of Weak Radiating Cells
The concept of a weak sound radiating cell is proposed to reduce the low frequency radiated noise from structures. The cell consists of two coupled surfaces such that, when placed on a vibrating structure, the responses of the two surfaces are nearly out-of-phase and of equal strength over a wide …
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The optimal design of transducers for active control of multiple-frequency structural sound radiation
… locations of actuators with which the radiated sound power from the plate is minimized. Also, the optimization of the piezoelectric actuator locations has been conducted for the active control of sound radiation from plates under heavy fluid loading. In this dissertation, two types of approaches …
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Optimization of transducers for active structural acoustic control of complex structures using numerical techniques
… and locations to minimize the total radiated sound power from complex structures has been developed. This optimization procedure interfaces finite and boundary element models with non-linear optimization techniques. The optimization procedure was used to perform parametric studies of Active …
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An investigation into inconsistencies between theoretical predictions and microphone array measurements of railway rolling noise
… the microphone array gives a correct estimate of sound power radiated by the rail. A comparison in terms of noise and rail vibration has been carried out for six wheel/rail conditions of Japanese railways. The TWINS predictions show good agreement with the measurements. After confirming the …
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A Study of Smart Foam for Noise Control Applications
… function of smart foam is to yield broadband sound attenuation. Passive acoustic foams are a very reliable high-frequency sound reduction method. With regard to smart foam, the embedded piezoelectric actuator is introduced to overcome the limitations of the passive foam in the low-frequency …
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Prediction of performance criteria for passive heating ventilation and air conditioning silencers
… criteria (insertion loss, regenerated sound power, and pressure drop) associated with a passive silencer is of great importance to the HVAC engineer. The purpose of this thesis is to predict the performance criteria listed above. Empirically derived regression equations are provided …
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