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Software sound level meter
Kotalík, Milan ; Říha, Kamil (referee) ; Sysel, Petr (advisor)
V této závěrečné práci se zaobírám problematikou měření hluků. Popisuji lidské vnímání zvuku a vysvětluji základní parametry a veličiny zvuku podle normy ČSN EN 61672-1. Dále se zaobírám problematikou měření zvukových veličin v reálném čase. Vytvářím ucelený soubor funkcí pro měření hladin zvuku v prostředí MATLAB, které se pokouším implementovat v jazyce C++ pomocí jeho JUCE framework.
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Analysis of the effect of friction modifiers composition on adhesion and noise in rail transport
Suchomel, Ondřej ; Galas, Radovan (referee) ; Klapka, Milan (advisor)
The aim of this bachelor thesis is experimental study of influence of composition of water based friction modifier on adhesion and sound pressure level. Experiments are carried out on twin-disk device. Introductory experiments are conducted to determine the conditions for further experiments. The experiments of the individual components follow, and the various friction modifier compositions are tested. From the results, it is obvious that a significant influence on the reduction of adhesion coefficient and sound pressure level has solid lubricant.
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Acoustics of small fans
Hájková, Lenka ; Rubina, Aleš (referee) ; Cifrinec, Ivan (referee) ; Hirš, Jiří (advisor)
Dissertation thesis falls within area of indoor climate and deals with investigation of acoustic microclimate in sanitary rooms of residential buildings during a mechanical ventilation. Sources of a noise in these areas are small fans. The thesis contains the evaluation of the existing situation concerning the referred issue, physical laws of acoustics and theoretical basics of acoustics of air conditioning. The part of the thesis is experimental measurement which aims to evaluate the situation in real applications and the possibility of influencing the acoustic microclimate by affixing of small fans on the building structure. The work contains a model for the verification of certain anticipated dependencies and theoretical investigation of the distribution of sound pressure levels in the sanitary room, depending on the location of the noise source. The last part of the work offers possible measures to improve the acoustic microclimate and elimination of the noise in sanitary rooms and in protected areas of residential buildings.
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Automated Processing of Acoustic Measurements
Kaláb, Vojtěch ; Kurc, David (referee) ; Schimmel, Jiří (advisor)
The goal of the Semestral thesis is to develop and describe application for automatized processing of the outputs from sound level meter NTi XL2. Application is developed in Integrated Development Enviroment Visual Basic for Application and realized in Microsoft Excel. It evaluates various types of outputs, processes its results and display the measurement protocol, including graphs of selected variables and measurement uncertainty. Theoretical part is focused on electroacustics required for understanding and processing measurement.
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Evaluation and modelling of Traffic Noise
Černoch, Adam ; Spies, Karel (referee) ; Kudrna, Jan (advisor)
The task of the master's thesis is introduction with the problems of traffic noise, focusing on noise from road traffic. There is a description what is the noise, how it is formed, its resources and what are the methods of measuring. The following are the various noise reduction measures such as noise barriers and low noise pavements. The main attention is devoted to the noise generated at the tire / road that is reduced by these pavements. The practical part describes the implemented measurements on individual sections at various locations in our country. The measurement was carried by slightly modified method CPX with reference tire directly at the vehicle. The main aim was to evaluate the measurement data, make comparison of different low-noise surfaces with each other and with the commonly used surfaces. Then quantification of the rate reduction of the noise emission for a given section and verification of input data for noise modeling. In conclusion, the obtained results are summarized and based on them were confirmed very good acoustic properties with the recommendation to continue with measurements in the future.
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Finite element modelling of sound pressure around the human head during phonation
Švancara, P. ; Tomeček, V. ; Horáček, Jaromír ; Švec, J. G.
The study presents finite element (FE) model of sound propagation through the vocal tract and around the human head during speech production. Similar experimental studies are not easily realisable. The FE model of the acoustic spaces corresponding to the human vocal tract for Czech vowel [a:] and acoustic space around the human head was created from computer tomography (CT) images. Modal and transient analyses (excitation by a short pulse) are used for analysis of resonant characteristics of the FE model. The production of vowel is then simulated using transient analysis of the FE models excited by Liljencrants-Fant’s (LF) glottal signal model. Formant frequencies detected from computed spectra are in good agreement with results of modal analysis and with literature. The results of numerical simulation enable evaluating of the transfer functions between a reference point and any point in the space around the head.
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