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Nanometric vibrometry
Ševčík, Michal ; Schimmel, Jiří (referee) ; Škarvada, Pavel (advisor)
This thesis deals with the precise measurement of distances in nanometer range at ultrasonic frequencies for the purposes of vibrometry. The paper is primary focused on~nanometric displacement measurement methods. First the thesis deals with the physical phenomena based on light in the theoretical section. This includes interference of light, index of refraction, polarization, interferometry and more. Understanding of these physical laws is crucial for design and assembling of the interferometer. Subjects of interferometric method for precise and fast measurement of the nanometric displacement and vibration are discussed. Interferometer components such as lasers, photodetectors and optical elements are described are described in the final part of this section. Practical section of thesis can be divided into two parts. The design and assembling issues are discussed in the first section. Many problems which I had to solve are described. Control software and implementation of the signal processing is the subject of the second part. I met with particular problems such as phase unwrapping. I solved this problem of discontinuous phase field with user written algorithm. Finally the graphical user interface was created. Using assembled interferometer and written software application I measured vibration of Langevin transducer on ultrasonic frequencies.
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Using masking effects for audio data watermarking
Kabourek, Jiří ; Schimmel, Jiří (referee) ; Zezula, Radek (advisor)
In this work is presented technique for embedding digital watermark in digital audio signals. Digital watermark must be imperceptible and should be robust against attacks and other types of distortion. Algorithm is implemented for embedding digital watermark using technique spread-spectrum and psychoacoustic model ISO-MPEG I layer I. Robustness was tested for filtering signal, MP3 compression and resample method.
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Sound panning in multichannel sound systems
Orlovský, Kristián ; Schimmel, Jiří (referee) ; Balík, Miroslav (advisor)
This thesis is aimed at simulation of auditory space. The first part is based on theoretical information and explains two of the most frequently used sound panning methods: Vector Base Amplitude Panning and Ambisonics. It shows the ways for sound panning by these methods. In next step are methods compared based on theoretical information and simulations in Matlab environment and one most suitable method is chosen for using in second part. This part describes image source method which enables parameters computation of direct sound wave and optional number of early reflections in rectangular room. Also is focused on problem of frequency dependent reflections. In conclusion it offer knowledge obtained by simulation of different auditory spaces with different topology.
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Simulation of Audio Signal Distortion in Perceptual Audio Encoder
Peloušek, Tomáš ; Rajmic, Pavel (referee) ; Schimmel, Jiří (advisor)
This thesis deals with the issue of the creation of a programme that would simulate the distortion that appears during the process of lossy audio coding. As the environment for the creation, the MATLAB programming language has been chosen. An encoder, which changes the subjective signal quality according to customer preferences for the bitrate, has been created as a practical part of this thesis. Its function is based on a dynamic bit allocation technique and includes an optional window switching algorithm. The theoretical background for the creation of the programme consists of an explanation of the main principles of lossy coding with emphasis on MPEG1 layer 3 operating principles. The practical chapter describes how the created programme and its parts work, and it includes results of the run quality testing. The testing was conducted using the objective assessment method PEMO-Q, and consisted of comparing the objective quality of the programme’s outputs to the quality of samples on which a regular MP3 encoder with identical settings was used.
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Laboratory Practices Focused on Loudspeaker System Design
Vydarený, Ján ; Balík, Miroslav (referee) ; Schimmel, Jiří (advisor)
This work deals with creating the bases for the laboratory tasks of designing the speaker system. The theoretical part explains the TS parameters and the equations for their calculation, the different types of sounding and switches. The work deals with selecting a suitable high-tone speaker to the specified low-tone speaker. Closed and bass reflex simulations were performed in the LspCAD. Similarly, simulation of the loudspeaker network was created in this program too. A loudspeaker box, crossover and subsequent measured parameters of the resulting repro system were produced. The last step was to modify the lab instructions
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Modern Methods of Time-Frequency Warping of Sound Signals
Trzos, Michal ; Rakús, Martin (referee) ; Průša, Zdeněk (referee) ; Schimmel, Jiří (advisor)
Tato práce se zabývá reprezentací nestacionárních harmonických signálů s časově proměnnými komponentami. Primárně je zaměřena na Harmonickou transformaci a jeji variantu se subkvadratickou výpočetní složitostí, Rychlou harmonickou transformaci. V této práci jsou prezentovány dva algoritmy využívající Rychlou harmonickou transformaci. Prvni používá jako metodu odhadu změny základního kmitočtu sbírané logaritmické spektrum a druhá používá metodu analýzy syntézou. Oba algoritmy jsou použity k analýze řečového segmentu pro porovnání vystupů. Nakonec je algoritmus využívající metody analýzy syntézou použit na reálné zvukové signály, aby bylo možné změřit zlepšení reprezentace kmitočtově modulovaných signálů za použití Harmonické transformace.
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Application for Programming MIDI Controllers
Dolejší, Miloš ; Frenštátský, Petr (referee) ; Schimmel, Jiří (advisor)
This bachelor thesis deals with designing of an application which allows programming of controls on ControlFREAK and Bitstream 3x controllers via MIDI System Exclusive messages. The theoretical part contains an analysis of the MIDI communication protocol, including description of channel and system MIDI data. The practical part describes individual parts of the application and then presents and explains parts of the source code. The application has been created in the Visual Studio 2013 SDK using Windows Multimedia System library, which contains functions and structures necessary for accomplishing the application’s tasks. The communication between the PC and the controller is realized via MIDI-USB converter.
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Laboratory design of a speaker system
Šulc, Martin ; Schimmel, Jiří (referee) ; Špiřík, Jan (advisor)
The bachelor thesis deals with the project of loudspeakers using freely available computer softwares. The thesis is focused on creation of a laboratory exercise called Laboratory design of a speaker system. The basic quantities describing acoustic wave motion and the principles of acoustic spread are explained there. There are also described different parts of loudspeakers like cabinets, loudspeaker drivers and electrical crossovers. Different softwares were chosen for the design. The descriptions of the most convenient programs for the laboratory exercises are introduced in the thesis. The laboratory exercise is devided into three parts. In the first part there is a brief theoretic introduction, the second part describes the control of the chosen software and the third part deals with the topic of this thesis. I have chosen two different sreeware softwares the most convenient for the construction of loudspeakers.
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Simulation of Sound Field of Sound System with Multiple Speakers in Closed Space
Brůna, Michal ; Husník, Libor (referee) ; Schimmel, Jiří (advisor)
In this thesis basic principles of sound system design are presented. A software simulation in Matlab is written for prediction of sound field with sources of real directivity in both freefield and in a closed room using velocity potential. Reflections are simulated using mirror sources of first and second order. Frequency dependent sound absorption coefficients are implemented in the simulation. There is a GUI designed to operate on most common horizontal configurations. Those are then evaluated and advantages and dissadvantages are demonstrated using the simulation software.
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Analysis of Acoustic Space Objective Quality Criteria of Orlí Street Theatre
Bělunek, Adam ; Frenštátský, Petr (referee) ; Schimmel, Jiří (advisor)
The core of the theoretical part of this work lies in a summary of basic laws and principles of a room acoustics, behavior of sound waves, reverberation time, sound absorption, impulse response and methods of measurement. Furthermore, the work describe and define some of the objective quality criteria of concert halls we know. We can find basic time criteria (e.g. reverberation time, early decay time, bass ratio, high frequency ratio…) and energy criteria (e.g. objective clarity, strenght of arriving energy…) etc.. The main focus is on a script, that is programmed in Matlab. It handles calculation of some objective quality criteria of concert halls. The function of the program is described. There are some trial calculation, that are evaluated. Functionality is demonstrated on some impulse responses, that were measured in hall of a theatre Divadlo na Orlí. The positions of microphones were different and also the configuration of acoustics elements in this hall was changing. Results were compared and commented. Another part of this work are scripts for calculations of impulse response and frequency response.
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