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Near-field measurement of a modular subwoofer unit
Borodáč, Samuel ; Schimmel, Jiří (referee) ; Balík, Miroslav (advisor)
The bachleor thesis describes influence of the type of loudspeaker baffle and methods of measuring the subwoofer unit on the frequency response at low frequencies. The work describes the configuration of measurements and the procedure in the analysis software APx500, as well as the export and evaluation of measured values. Moreover, the thesis also includes the results of measurements, its brief analysis and observation of phenomena affecting the measurement of the modular frequency response of the loudspeaker unit in the near field, as well as achieving the overall resulting frequency response of the loudspeaker unit.
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Antenna for mobile high power microwave generator
Kračmar, Leoš ; Láčík, Jaroslav (referee) ; Mikulášek, Tomáš (advisor)
The bachelor thesis deals with the design and practical implementation of a magnetron connected to waveguide as an excitation source for a linear slot antenna array. The goal was thorough acquaintance with the issue of partial parts of designs, verification of calculated parameters using software simulations and practical measurements on manufactured parts of the project. In the first part of the work, it theoretically deals with used components, used parameters and by software design of a magnetron to waveguide transition model with practical measurement. The second part of the work contains calculations and simulations of the design of a linear slot antenna array, which continues by series of practical measurements of antenna properties.
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Standard baffle - laboratory device
Hodinka, Tomáš ; Říha, Kamil (referee) ; Balík, Miroslav (advisor)
The purpose of this project is the design and the construction of a laboratory preparation for loudspeaker measurements, a standard baffle. Standard baffle is a rectangular panel with a loudspeaker placed eccentrically. Measurements with this baffle are then done in an anechoic chamber. The main purpose of a standard baffle is the ability to measure loudspeakers without the effect, that is caused by the pressure properties of a closed baffle and without an acoustic short circuit. The standard baffle is designed, so that it is self-supporting, transferable by 2 people, easy to be stored, modular and able to support loudspeakers that are up to 12 inches in diameter. The designed baffle is detachable into 3 parts. The base, the panel, and the inserts. The base is a big, heavy board with a key on the upper side. This key fits into a key groove in the panel and that allows the two parts to assemble. The plane is made of four layers of different types of plywood. That allows the design to make a compromise between the toughness and weight. The inserts are designed, so that the replacement and manipulation of loudspeakers during measurement are as past and as simple as possible. During measurement the loudspeakers are mounted in their respective inserts, which can be mounted and dismounted from the standard baffle without any tools. The test measurements demonstrated that the standard baffle is unsuitable for reference measurements. Resonance of the plane, reflections from the base, refractions from the outer edges of the baffle and potentially different causes unduly distort the results of measurements. These distortions are displayed with a considerable consistency even between different loudspeakers. This indicates that these distortions could be filtered oud by, for example, using a specialized software.
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Test Rig Design Proposal for the Experimental Validation of Transmission Parameters in Open Loop Torque Condition
Máca, Jiří ; Janoušek, Michal (referee) ; Prokop, Aleš (advisor)
This final diploma thesis deals with the issue of vibration and noise measurement of transmission devices. The research part describes the basic issues of noise and vibration generation, their measurement, as well as sources of vibrations in gear units. The practical part deals with the design proposal of the attachment of the experimental single-stage gearbox and the load dynamometer to the anechoic chamber including the drawings. Further, by checking the modal properties of the proposed test stand, using the finite element method, the analytical and numerical control of the torsional vibrations of the rotating parts with respect to the expected frequency ranges of use.
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Flat Plates Noise
Zlámal, Josef ; Řehák, Kamil (referee) ; Prokop, Aleš (advisor)
The master thesis summaries the findings results of a study focused on the spread of noise vibrating flat plates. Part of this thesis is measurements of flat plate noise in the anechoic chamber and finally their processing and evaluation. The next part of the thesis is focused on FEM acoustic simulation and comparing results with measurements.
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Creating a database of audio recordings with artificial noise in an anechoic chamber
Hájek, Vojtěch ; Povoda, Lukáš (referee) ; Harár, Pavol (advisor)
This bachelor thesis deals with theory of creating the database of sound records and subsequent creating the database of speech records in the anechoic chamber. Database was created as training dataset for learning process of the artificial neural network, which will be able to separate the speech from background noise. Therefore as the part of the database there are also the recordings of various types of noise that will be used as background noise for the voice recordings. The dataset contains records taken from 18 speakers aged from 16 to 76 years. Half of the speakers were men, half women. Database contains 405 records of speach of average length 46,7 secons and total length 315 minutes. By combining each speech record with each noise record at three levels of signal-to-noise ratio was created 7290 mixed records.
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Sound power level estimation principles
Fajt, Jakub ; Řehák, Kamil (referee) ; Prokop, Aleš (advisor)
This Master´s thesis deals with principles of determination of the sound power level. At the very beginning there is an explanation of important concepts. Afterwards there is an overview of standards that deal with the sound power level determination, including the ČSN EN ISO 9614-1 standard which is used for the experiment. Last but not least, there is described the experiment, consisting of several measurements of the same object, but every time with different configuration of measuring and sound reflective surfaces.
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