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Audio codecs and their perceptual quality evaluation
Hudec, Andrej ; Schimmel, Jiří (referee) ; Rajmic, Pavel (advisor)
The bachelor thesis deals with audio codecs and tests to evaluate their listening quality. The thesis offers a description of the properties of human hearing, a brief introduction to the issues of audio coding, types of audio data compression and listening tests. The bachelor thesis also contains a theoretical description of the coding processes of selected audio codecs, evaluation of measuring their computational complexity and evaluation of listening quality of each of them using listening tests. HTML, CSS, Javascript and Python programming languages were used to implement the listening test environment. The audio files examined in the listening tests were obtained using the FFmpeg library.
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Subjective and Objective Assessment of Speech Quality
Bezdíček, Martin ; Balík, Miroslav (referee) ; Vondra, Martin (advisor)
This Bachelor's thesis is focused on subjective and objective methods for evaluation of speech quality. In the first part, the quality of transmitted speech signal and its distorting effects are given. Futher, subjective and objective methods for evaluation of speech are described. The objective methods: Signal to Noise Ratio (SNR), Segmental Signal to Noise Ratio (SSNR), the methods for evaluation in spectral area (Log Likelihood Ratio Measures and Cepstral Distance) and also Perceptual Evaluation of Speech Quality (PESQ). The next part deals with the correlation analysis which is used for the comparison of subjective and objective methods. In the last part of the bachelor thesis the results of subjective and objective methods are presented. Finally on the basis of correlation analysis with the results of subjective method, the best objective method is recommended.
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Analysis of the perception of chords in a space with different reverberations
Adamkovičová, Lenka ; Musil, Jaroslav (referee) ; Jirásek, Ondřej (advisor)
This bachelor’s thesis is dealing with an analysis of subjective perception of chords in spaces with different reverberation parameters. An algorithmic reverb with 5 different settings of parameters was used on 32 chords or intervals created by either additive synthesis or from sampled real instruments. The modified sounds were then judged on 5 different bipolar scales by 100 respondents in a listening test. The goal of this work was to find the influence of reverbs with different parameters on perception of dissonance, pleasantness, roughness, and timbre of individual chords. Survey results were then plotted in graphs, in which they were compared to each other.
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Restoration of analog sound records form magnetic tapes
Spiššák, Filip ; Vrba, Kamil (referee) ; Rášo, Ondřej (advisor)
The aim of this bachelor thesis is a theoretical analysis of noises that often occur in magnetic audio tape recordings both from objective and subjective point of view. Furthermore, listening test is designed and carried out. In this test, the task of the listener is to evaluate the subjective variable „disturbance rate of unwanted sound in audio recording“ via specific software that was designed for this purpose. From the described noises, unwanted sounds represent the three most frequently occuring ones. It is a so-called „Hiss“ and two variations of „Hum“ noises. Hum is investigated in two dimensions so that the differences in the perception of even and odd harmonics can be analysed. Through a statistical analysis of the collected data, these noises can be classified according to the subjective perception of the specific recordings, which was also the primary purpose of this work. The findings of this thesis indicate that for instance Hiss is the most disturbing noise and that there is not a significant difference in the perception of even and odd harmonics. This information could be useful for the purposes of old record’s restorations, for example when an effort is made to remove specific types of noise. The measurement performed in this work may also help with the planning of other time-consuming and money-consuming listening tests.
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The Influence of single harmonics or formants on timbre color perception
Klimeš, Martin ; Indrák, Michal (referee) ; Jirásek, Ondřej (advisor)
This thesis is dealing with the research of the influence of individual harmonic on the perception of sound color. An application was created with a questionnaire in which respondents assessed a total of 29 samples on different bipolar scales.The samples were either modeled by additive synthesis or created by modifying musical instruments. The aim was to investigate how and what combinations of higher harmonic affect the perception of sound color. The experiment is based on the semantic differential method. The samples were divided into several groups and within these groups they were compared and related to the expected color perception.
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The Evaluation of masking of harmonic components in a mixture
Kovanda, Jindřich ; Indrák, Michal (referee) ; Jirásek, Ondřej (advisor)
This thesis deals with design and creation of listening test in which its respondents were setting certain harmonic of the tone to mixture of up to 16 harmonics. The respondents were setting intensity of the harmonic to the border position, in which the harmonic was not masked by the other harmonics in the tone and in which the harmonic stood up from the mixture. The respondents were stetting the harmonics from the first to sixteenth, in various types of the spectrum, pitch and intensity of the tone. Based on the results relations were found which determine how the perception of masking of harmonics vary with their order in the spectrum.
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Analysis of pitch perception depending on the spectrum
Slávik, Martin ; Indrák, Michal (referee) ; Jirásek, Ondřej (advisor)
This thesis is dealing with the research of the influence of individual harmonic components on the perception of sound height. As a part of the work has been made an internet questionnaire on a web address www.analyzavyšek.9e.cz, where individual respondents completed listening test compound of 46 samples. This experiment is based on semantic differential method. Individual samples are compound of sine wave – tone and examined sample, which respondents evaluates on three bipolar scales. The samples were either modelled by additive synthesis or modified sampled sounds of instruments. Individual samples were divided to four major groups and other minor groups for clarity. The purpose was to find which parts, combinations and harmonic components of sound and tone can affect perception of tone height.
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The analysis of psychoacoustic perception of chords composed from different full and variously colored signals
Vejmělka, Daniel ; Musil, Jaroslav (referee) ; Jirásek, Ondřej (advisor)
This thesis is dealing with the impact of frequency spectrum of musical sounds on psycho-acoustical perception of the listener. It studies how differently filled harmonic spectrums can influence listener’s ability to determine individual notes in a chord and what influence, on recognizability of a chord, inharmonic elements have. It explores different methods of psycho-acoustic measurements and further data processing. The experiment is based on a method of paired comparisons and was realized in a form of listening test with more than 100 participants. The test is focused on typical representatives of different groups of musical instruments. It studies the impact of different colors of sound used in different types of chords. It further deals with statistical processing of the recovered data.
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The Evaluation of masking of harmonic components in a mixture
Kovanda, Jindřich ; Indrák, Michal (referee) ; Jirásek, Ondřej (advisor)
This thesis deals with design and creation of listening test in which its respondents were setting certain harmonic of the tone to mixture of up to 16 harmonics. The respondents were setting intensity of the harmonic to the border position, in which the harmonic was not masked by the other harmonics in the tone and in which the harmonic stood up from the mixture. The respondents were stetting the harmonics from the first to sixteenth, in various types of the spectrum, pitch and intensity of the tone. Based on the results relations were found which determine how the perception of masking of harmonics vary with their order in the spectrum.
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