Design and implementation aspects of a small anechoic room and sound-actuation system

Abstract

Looking for future projects, the possibility to have optimum conditions to perform microphone tests and any noise measurements of different small devices which will be constructed in the university, the need to construct a anechoic chamber was considered, so in this thesis a research about anechoic chambers was made. An acoustic anechoic chamber is a shielded room designed for performing sound measurements under conditions close to free space. Due to the difficulties that might entail the construction of a large anechoic room, we addressed the design of a chamber with smaller dimensions. This way we try to have an enclosure with conditions close to free field and to be able to perform the necessary tests with a low-cost construction. The research group wants to build an environmental emulator to test their sensor networks that are used for environmental noise study. By using multiple small rooms they want to emulate a bigger space. This report summarizes the design and construction of a small anechoic chamber, with a focus on microphone testing. Finally a low cost prototype of a small anechoic room will be built, in which we would perform the tests. The prototype has been built with low cost materials that are MDF for the walls, and fiber glass for the absorbent material. A sound actuation system has been designed too. The latter being made up of an amplifier and two speakers. The first speaker is a coaxial speaker for generating pink or white noise or sweeps. The second speaker is the tweeter to generate pure tones. For the coaxial speaker it was necessary to build a baffle. A baffle was designed in order to achieve the best performance of the loudspeaker. Finally, the design was made for a small anechoic room. We took into account the Eigen-modes, the absorption, the insulation and predominant axis of measurement as major factors of consideration. So insulation, absorption and construction issues are detailed and addressed, creating a base for the experimental evaluation for a following project.