Measurement of the sound reduction index with a sound intensity analyzer using the proposed sound reduction box is an alternative low-cost and portable sound insulation testing method. The proposed sound reduction box is a miniature reverberation chamber for testing wood board samples as soundproofing material. The proposed sound reduction box is made from medium density fiberboard. The combination of the proposed sound reduction box with a sound intensity analyzer was able to produce similar reduction index measurement results as a standard sound insulation testing system.
It is needed noise control by limiting the sound energy emitted by the source. The total sound energy emitted by a sound source in all directions per unit time is called sound power. There are several methods for measuring the sound power level emitted by a sound source. This study is comparing the sound power levels of a reference source Brüel&Kjær Type 4204 using sound pressure done in anechoic rooms and hemi-anechoic rooms method (ISO 3745), using reverberation test rooms method (ISO 3741), and using the sound intensity method (ISO 9614-3). This study result that there is a small difference between those methods.
One of the benchmarks in air pollution is the quality of ambient air consisting of gas and particulate matter. Measurement of particulates in ambient air can be done using a High-Volume Air Sampler (HVAS). However, in the measurement process it sometimes causes noise annoyance to the community where the measuring instrument is operated, considering that the operating time of the instrument is 24 consecutive hours. This research identifies the value of the sound power level emitted from the several types of HVAS to the surrounding environment. There are two types of HVAS measured in this study consisting of one unit of HVAS with analogue flow control made by Indonesian manufacturer and two units of HVAS with digital flow control made by Japan and United States of America manufacturers. Sound power level is determined using ISO 9614 method with a sound intensity analyzer as the main instrument. The sound power level data for each HVAS were than compared and frequency spectrum distributions are evaluated. Based on the research results, it was found that some sample units emitted sound power levels of more than 90 dBA with dominant noise being at high frequencies starting from 4000 Hz. The results of the research can be used as an early information in the development of the HVAS regarding noise mitigation, because there is different approach for controlling noise specifics in low, mid and high frequencies noise source.
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