Search for dissertations about: "Frequency methods"

Showing result 1 - 5 of 1342 swedish dissertations containing the words Frequency methods.

  1. 1. Active Control of Propeller-Induced Noise in Aircraft : Algorithms & Methods

    Author : Sven Johansson; []
    Keywords : ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; active control of sound; active noise control; anc; actuator individual normalized filtered-x lms; filtered-x lms algorithm; newton algorithm; complex lms; multireference algorithm; leaky lms; control effort weighting; feedforward control; feedback contro;

    Abstract : In the last decade acoustic noise has become more and more regarded as a problem. In cars, boats, trains and aircraft, low-frequency noise reduces comfort. Lightweight materials and more powerful engines are used in high-speed vehicles, resulting in a general increase in interior noise levels. READ MORE

  2. 2. Pitch, loudness and frequency selectivity in low-frequency hearing loss

    Author : Jonas Brännström; Lund näs- och halssjukdomar Öron-; []
    Keywords : MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; frequency coding; Cochlea; frequency selectivity; hearing fluctuation; inner ear pressure; long-term measurement; Ménière s disease; low-frequency hearing loss; loudness; pitch.;

    Abstract : Patients with Ménière's disease and cochlear hydrops show fluctuating low-frequency hearing loss (FLFHL). At present these changes are followed as patients' subjective reports and occasional measurements. READ MORE

  3. 3. Low frequency noise during work. Effects on performance and annoyance

    Author : Johanna Bengtsson; Göteborgs universitet; Göteborgs universitet; Gothenburg University; []
    Keywords : MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Low frequency noise; performance; workload; annoyance; cortisol; subjective stress; subjective sensitivity to noise; sound characteristics; frequency balance; modulation frequency;

    Abstract : Aims. Low frequency noise (LFN) is defined as "a noise with a dominant frequency content of 20 to 200 Hz". Common sources of LFN in occupational environments are ventilation, heating and air-conditioning systems, computer network installations and compressors. READ MORE

  4. 4. Numerical Methods for Turbomachinery Aeromechanical Predictions

    Author : Maria Angelica Mayorca; Damian Vogt; Torsten Fransson; Robert Kielb; KTH; []
    Keywords : ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; Aeromechanics; numerical tools; methods; turbomachinery; aeroelasticity; gas turbines; vibrations;

    Abstract : In both aviation and power generation, gas turbines are used as key components. An important driver of technological advance in gas turbines is the race towards environmentally friendly machines, decreasing the fuel burn, community noise and NOx emissions. READ MORE

  5. 5. Hybrid Methods for Computational Electromagnetics in Frequency Domain

    Author : Stefan Hagdahl; Björn Engquist; Lars Pettersson; Stockholms universitet; []
    Keywords : NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Maxwell s equations; Geometrical Theory of Diffraction; Smooth Surface Diffraction; Boundary Element Method; Hybrid methods; Electromagnetic Scattering; Numerical analysis; Numerisk analys;

    Abstract : In this thesis we study hybrid numerical methods to be used in computational electromagnetics. The purpose is to address a wide frequency range relative to a given geometry. We also focus on efficient and robust numerical algorithms for computing the so called Smooth Surface Diffraction predicted by Geometrical Theory of Diffraction (GTD). READ MORE