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 28 for “"Noise Attenuation"”.
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Active noise attenuation
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1980.
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Adaptive Stochastic Systems: Estimation, Filtering, And Noise Attenuation
… switching.</p> <p>Next we consider problems in noise attenuation in systems with unmodeled dynamics and stochastic signal errors. A robust two-phase design procedure is developed which first estimates the signal in a simplified form, and then applies a control to tune out the noise. Worst-case …
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Numerical investigation of slat noise attenuation using acoustic liners
Noise generated by high-lift devices such as slats on a wing is a major contributor to the overall airframe noise during the landing approach of a commercial aircraft. In this work the concept of attenuating slat noise using absorptive acoustic liners in the slat/main element gap is explored using …
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Low Frequency Finite Element Modeling of Passive Noise Attenuation in Ear Defenders
Noise levels in areas adjacent to high performance jets have increased monotonically in the past few years. When personnel are exposed to such high noise fields, the need for better hearing protection is inevitable. Adequate hearing protection may be achieved through the use of circumaural ear …
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Low Frequency Modeling and Experimental Validation of Passive Noise Attenuation in Ear Defenders
… an effective way of protecting users from high noise fields. Over the decades, a number of researchers dedicated their time to understanding the dynamics that govern the attenuation of hearing protectors. This thesis duplicates some of this work with newer technology and better data processing …
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Laboratory investigation of in-field influences on spectral noise attenuation and comfort of insert and circumaural hearing protectors
… manufacturer-supplied hearing protector attenuation ratings typically overestimate the workers' protection level In the workplace. In addition, several work-related in-field factors often degrade protection performance of the hearing protection devices (HPDs), posing the threat of …
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Field evaluation of noise attenuation and comfort performance of earplug, earmuff, and ear canal cap hearing protectors under the ANSI S12.6- 1984 sound field standard
… study was conducted to determine the actual noise attenuation and perceived comfort achieved by 40 noise-exposed industrial workers in 5 industrial workplaces wearing 4 different industrial hearing protection devices (HPDs) while on the job. Over 2 consecutive 3-week periods of HPD use, the …
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Development of a Weatherproof Windscreen for a Microphone Array
… windscreens are typically used to reduce the noise associated with wind flowing over a microphone diaphragm by reducing the velocity of the airflow. While most windscreens are effective at reducing this noise, they do not protect the microphone from many natural elements, such as moisture, …
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INVESTIGATIVE STUDY OF CONTROL DESIGN FOR A CLASS OF NONLINEAR SYSTEMS USING MODIFIED STATE-DEPENDENT DIFFERENTIAL RICCATI EQUATION
… H-inf; robust control design for a constant noise attenuation bound, when the solution exists. To reduce the design conservativeness, the technique is further extended to state-dependent H-inf; robust control design with adaptive noise attenuation bound, using gain-scheduling technique and …
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Low complexity quantized controllers for LTI systems : peak-to-peak performance guarantees
… scheme for unstable LTI systems performing noise attenuation via a finite-rate digital channel. In the first part of the thesis, we introduce the structure of the control system as well as the encoder and decoder used to transmit the required control signals along the digital channel. The …
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Finite Element Modeling and Exploration of Double Hearing Protection Systems
Noise levels in modern industrial and military environments are constantly increasing, requiring the improvement of current hearing protection devices. The improvement of passive hearing protection devices lies in examining the performance of major contributors to reduction of noise attenuation. …
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Fan noise reduction from a supersonic inlet
… conducted to investigate the radiation of fan noise through a supersonic inlet. A scaled-down model of an axisymmetric, mixed-compression, supersonic inlet (P-inlet) was used in conjunction with a 10.4 cm (4.1 in) diameter turbofan engine simulator as the noise source. The tests were conducted …
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Advanced control of MEMS probing devices
… model uncertainty and instrumentation noise. In this article, a systematic control design from robust control approach is demonstrated on a micro probing device with electrically separated sensing combs and driving combs. The system is identified through experimental input-output data …
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EMI Noise Reduction Techniques for High Frequency Power Converters
… switch mode power supplies will cause severe EMI noise issue. In a typical front-end converter, the EMI filter usually occupies 1/3 to 1/4 volume of total converter. Hence, reducing the EMI noise of power converter can help reduce the volume of EMI filter and improving the total power density of …
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Tilt-Compensated Magnetic Field Sensor
… smoothing inclination signal irregularities and noise. Trigonometric conversions necessary for tilt-compensation are calculated in software using traditional methods, as well as the Coordinate Rotation Digital Computer (CORDIC) algorithm. Both calculation methods are compared for execution time …
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X-ray microscope performance enhancement through control architecture change
… high resolution, disturbance rejection and noise attenuation. Conveniently, the field of scanning probe microscopes (SPMs) have already flourished on this aspect of controller algorithms proven to give desired closed-loop properties. Controller algorithms such as Proportional Integral …
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Spectral attenuation and wearability of circumaural hearing protectors as influenced by design attributes and work-related activity
… (HPDs), a widely used countermeasure against noise-induced hearing loss, are laboratory-tested for their attenuation (noise reduction) capabilities. Unfortunately, laboratory tests overestimate the in-workplace performance of the devices, potentially leading to inadequate protection for the …
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Acoustic optimisation and prediction of sound propagation in turbofan engine ducts
… in this thesis explores the prediction of noise propagation and<br/>radiation in turbofan engine intakes and bypass ducts, and the optimisation of noise attenuation<br/>by using acoustic liners. A commercial FE/IE code ACTRAN/TM is used<br/>within two shell programs; B-induct for bypass …
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Optimal placement of sensor and actuator for sound-structure interaction system
… by experimental vibration and acoustic noise attenuation for arbitrary disturbance using feedback controllers with optimal placement of actuator and sensor. The disturbance is experimentally set to enter the system via a spatial location different from the controller input as would be in …
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Topology Investigation and System Optimization of Resonant Converters
… Based on the proposed model, EMI analysis and noise attenuation techniques are proposed and verified by experiments. Thirdly, startup and over-load protection are another issues of LLC resonant converters. With proposed multi-element resonant converters, the current limit issues can be …
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