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Three-way stereo speaker system with bassreflex
Burget, Jan ; Schimmel, Jiří (referee) ; Kratochvíl, Tomáš (advisor)
This bachelor‘s thesis contains complete design of three-way stereophonic loudspeaker sound system with bassreflex. There is detailed description of selection of acoustic transducers, their measurements and adjustments. As an integral part of this seminar study is design of loudspeaker baffle and calculations or simulation of bassreflex. And further,this study also deals with a design of loudspeaker crossovers and their simulation. The study contains structural elements as a PCB (printed circuit board) or 3D pattern and drawings of loudspeaker box. KEYWORDS
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Design and implementation of MIDI driver
Jirčík, Zdeněk ; Slanina, Martin (referee) ; Schimmel, Jiří (advisor)
This bachelor thesis describes design and implementation of a MIDI controller that will transmit messages to MIDI program change and MIDI continuous messages that the value of the MIDI controller standard type. The theoretical part describes communication using the MIDI protocol, its implementation in microprocessor and controls the LCD controller. The practical part deals with the design and implementation of the MIDI controller. The result of this work is a circuit diagram, PCB, microprocessor control program and construction of MIDI controller.
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Compensation of Loudspeaker Frequency Response for a Wider Listening Area
Beránek, Šimon ; Říha, Kamil (referee) ; Schimmel, Jiří (advisor)
This bachelor thesis studies problematics of calculating average impulse responses of rooms. Measuring signals like MLS or linear/exponential sine sweep are described. Basic methods of interpolation are explained and their applicability in frequency response calculations is described. Digital filters are explained as a tool for frequency response equalization. First part of this thesis tests methods of interpolation on 64 measured impulse responses. These methods have been further optimized and one was chosen to calculate the average impulse response for each of the measured rooms. Second part consists of AB*X listening tests deployed to find subjective aural differences of the interpolated impulse responses and few of the measured impulse responses. These interpolated impulses responses were further compensated using a warped filter library.
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Control of Bang&Olufsen Products Using Bluetooth Technology
Mandík, Martin ; Hanák, Pavel (referee) ; Schimmel, Jiří (advisor)
This master thesis deals with the creation concept of the Bluetooth module and applications for mobile phone and PDA. After the connection of the concept with remote control, enable extend of control the Bang&Olufsen products with using mobile phone or PDA. Applications in mobile phone or PDA will communicate to the concept of using Bluetooth technology. The result of this thesis is the creation of printed circuit boards and applications for mobile phone and PDA.
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Design and Measurement of Parameters of Acoustic Diffusors
Burda, Jan ; Vrba, Kamil (referee) ; Schimmel, Jiří (advisor)
This work focuses on the issue of acoustic diffusers. The introductory chapter describes the necessary theory of the sound distribution through enclosed space. Acoustic fields are also described. A description of the different diffusion element types and theirs design methods follows. It focuses mainly on design, which uses pseudo-random mathematical sequences. The aim of the work is to produce several types of acoustic diffusors and to verify their diffusion properties by means of measurements. The work uses the AFMG Reflex to simulate the diffusion properties of the proposed elements. Further, the thesis contains a description of the diffusion properties measurement process by the boundary plane method and the process of evaluating the measured data using the Matlab program.
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Compensation of loudspeaker measurements using standard baffle
Štěpáník, Jiří ; Schimmel, Jiří (referee) ; Balík, Miroslav (advisor)
The frequency response of the loudspeaker is one of the key data that needs to be known, for example, when designing a speaker cabinet or speaker system. The frequency response should be achieved with the highest possible accuracy and with a minimum of distortion. How to achieve such characteristics is described in the standard ČSN EN 60268-5, which states as one of the ways the use of standard enclosures. Except for the standard baffle, these baffles have correction curves for the measured characteristics described in the standard. However, this does not mean that the standard baffle does not distort the measurement. The aim of this work is to analyze the distortion of measurements caused by this baffle and other elements and their compensation. The work contains a description of certain parts of the standard ČSN EN 60268-5 with focus on the standard baffle. Especially on its construction and methods of measuring the speakers mounted on it. Several test measurements were performed within the work. These measurements were performed in a anechoic chamber with speakers mounted on a modular standard baffle, which is a modification of the standard baffle which is also described in the work. The measurements performed include the measurement of frequency characteristics at different distances of the microphone from the speaker at different positions of the baffle in the anechoic chamber. The test measurements show that the modular standard baffle and anechoic chamber cause measurement distortion. In other measurements, the distortion by the anechoic chamber is minimized and the distortion caused by the base of the modular standard baffle is completely eliminated. The thesis then presents the theory of sound diffraction at the edges of a standard baffle and the theory of the extended Biot-Tolstoy-Medwin method of modeling these diffractions using numerical calculations. Based on this theory, software compensation of diffraction distortion was performed in Matlab. It is not entirely clear from the results of the compensation to what extent it can be considered successful. It can be speculated that it only works on certain frequencies. It is necessary to verify the functionality of this compensation method by another test measurement.
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Beamforming using microphone arrays
Bartoň, Zdeněk ; Schimmel, Jiří (referee) ; Míča, Ivan (advisor)
The aim of the master thesis is to sum up theoretical information about beamforming methods of microphone arrays and to verify their functionality. At the beginning of this work there are simulated different varietes of linear uniform and nonuniform microphone arrays and circular arrays. The results are verificated by a practical measurement in ideal conditions. Then I will focuse on implementation of the DAS(Delay And Sum), SAB(Sub Array Beamforming), CDB(Constant Directivity Beamforming), CDB-CA(CDB-Circular Arrays) beamformer including theoretical and practical verification of the functionality in ideal conditions. At the end of this thesis are all beamforming methods compared with each other at SNR(signal to Noise Ratio) and directivity parameters.
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Software Sound Level Meter
Menšík, Václav ; Sysel, Petr (referee) ; Schimmel, Jiří (advisor)
This thesis discusses noise measurement devices, design and implementation of a software sound pressure meter. Sound pressure meter requirements specified by the IEC 61672 standard and selected acoustic physical properties are discussed. Further, the JUCE framework is presented along with an of the graphical user interface and digital signal processing capabilities of the SoundMeter program.
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Audio amplifier controlled by the IP protocol
Dvořák, Petr ; Schimmel, Jiří (referee) ; Kouřil, Jiří (advisor)
The bachelor thesis is intent on projection and realization of a device whitch is capable of communicate with a remote client through the Ethernet making use of the protocol set TCP/IP. This communication will be used for the control of analog and digital outputs of the device, which is able to be attached to any amplifier of audio signals. One of used protocols is UDP. This protocol is closely described, because it is used for transfer of data controlling outputs. The whole device is controlled by microprocessor ATmega32, which operates the communication with the ethernet interface through the controller ENC28j60, the communication with the D/A converters MCP4922 and controlling of digital outputs and a display. The device has its own IP and MAC address for identification in the network. It is possible to edit both addresses in the menu of the device with the help of the module LCD, the display of 2x16 characters with fours buttons. The audio amplifier staffed by the voltage controlled by the computing amplifiers SSM2018T is connected to this device. The amplifier is proposed as six-channel with symmetric inputs through the connectors XLR and unsymmetric outputs through the connectors CINCH. The operating programme which is able to be run on PC with the operating system Windows is necessary for the remote control of the device in the network and all functions of the device are controlled by this programme. This programme enables to control the device after setting the IP address of the destination device and the communication establishment. The motherboard is proposed as a universal module which keeps at disposal up to 6 analog outputs with the range of the control voltage 0 – 5 V and up to 21 binary inputs/outputs.
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Objective Criteria for Room Acoustics Assessment
Zwins, Jiří ; Kurc, David (referee) ; Schimmel, Jiří (advisor)
The aim of this thesis is to define basic concepts of acoustics, a closer acquaintance with the defined objective criteria for evaluation of acoustic spaces and practical processing algorithms in Matlab. The central part is presented technique of calculating the reverberation time by integrating the measured room impulse response and its graphical output. The reverberation time is just one of objective assessment criteria acoustic spaces. The calculation algorithm is based on the principle of a closed space Dirac excitation pulse and the subsequent decline in energy determination of the reverberation time of the acoustic pressure. The analysis of the data samples were used specified areas in VUT Brno.
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