Análise de performance de um enclausuramento por meio de medição de potência sonora em câmara reverberante

Abstract

This paper presents the design, construction and evaluation of an acoustic enclosure, which was used as basis for the study of the sound insulation caused by these devices. An acoustic enclosure is a passive noise control measure used on a sound source, involving it with an arrangement of materials that act on the attenuation of sound energy from the internal absorption to the transmission loss. A suitable design for an enclosure should result in a considerable decrease in the sound energy radiated by a source in an environment. The project presented in this paper was designed to have different stages of enclosing, being possible to close it completely or to fit side attenuators that allow internal ventilation, simulating a typical case of a machinery enclosure in industrial plants. Inside the enclosure, a coating of soundabsorbing material was used, allowing the observation of its influence on the sound field inside of the enclosure. To verify the efficiency of the project, measurements of sound levels were carried out in a reverberant field based on the ISO 3741 standard, used to determine the sound power of noise sources. The measurement environment was the reverberant chamber of the Acoustical Engineering laboratory at the Federal University of Santa Maria, while the sound source used was a dodecahedron (omnidirectional sound source), which was subjected to the enclosure. The study was carried out from the determination of the sound transmission loss that the enclosure exerts on the sound power emitted by the source. The calculation of the sound power is given by the comparison method and the direct method. It was concluded that the enclosure performance for both methods was very close, with a variation of only about 1 dB. The performance of the closed enclosure with sound-absorbing material was superior to the others, with 26 dB of insertion and transmission loss. It was also possible to observe the effectiveness of adding internal discontinuities and absorbing material in the system, with insertion and transmission losses reaching close to 20 dB for both stages of enclosure with attenuator with discontinuities and attenuator with sound-absorbing material.