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Impedance tube for measuring sound absorption coefficient and transmission loss coefficient
Hodinka, Tomáš ; Balík, Miroslav (referee) ; Skvaril, Šimon (advisor)
The goal of this thesis is the design and manufacture of the mechanical and electrical components of the impedance tube. The impedance tube is a tool used in laboratories, that has its parameters dictated by norms. On one side of this enclosed airtight tube is a speaker, and on the other the measured material. By switching some additional parts, the tube is capable of measuring not only the acoustic absorption, but also sound penetration. Impedance tube is made, so that it is robust, easy to manipulate and use, and easy to store. The designed impedance tube can measure the sound penetration of any material, that is up to 50mm in thickness, and the acoustic absorption of materials that are up to 120mm in thickness. Parts of the tube, that are directly welded to the tube itself are made of the same metal that the tube itself is, and the speaker enclosure is made from plywood. Along with the assembly of the impedance tube, a complete and detailed drawing documentation for future recreation is added, along with a suitable amplifier and all peripherals necessary for measurements.
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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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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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