Author: Yeung, Chi-wai Stephen
Title: Computer optimized acoustic design at a plant room
Degree: M.Sc.
Year: 1997
Subject: Acoustical engineering -- Data processing
Architectural acoustics
Noise control
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: 56, [157] leaves : ill. (some col.) ; 30 cm
Language: English
Abstract: The objective of this project is to find out the feasible ways to achieve the optimal acoustic design in a plant room with assist by the computer-aid program. The methodology used in the project is to make use of the programmed spreadsheet to calculate the acoustic performance within system and to set up an algorithm so as to find out the optimized result from the calculated solutions based on both acoustic and ventilation criteria. This project is to focus on a simple model, which includes the fan, silencer and plant room. The reason for this selection is that the fan represents the major noise source item of the ventilation system whereas the silencer stands for the core part of the acoustic treatment. The spreadsheet provides a fast and convenient way to determine the feasible solutions at various combinations of the said components in the simple model. In respect of the analysis of the results obtained, the energy consumption is the first criteria for determining the optimized combination in the system. A general design algorithm is worked out as the guide for the designers to evaluate their own optimized solution. A full simulation is suggested to be used in the analysis as to determine the optimized solution within the system. Apart from the simulation method, there are other effective ways to find out the optimized solutions in the system. The results of the commercial silencer (dissipative type) are not always good enough to meet with the attenuation requirement for the typical fan which dominates at 63 Hz or 125 Hz since it usually experiences a substantial decrease in performance at low frequency bands (below 250 Hz) and becomes over-attenuated at high frequency bands. Therefore, the only solution is to increase the length of the silencer in order to compensate for their low frequency limitation. However, it in turn requires extra energy to compensate for the additional pressure drop of the silencer. Thus, a new type of silencer is required to suit for the special noise spectrum of the fan. Some experimental works have recently been carried out to test the performance of the new reactive silencer (side branch attenuator) in the ventilation system. According to the experimental results, the new silencer can achieve better attenuation at low frequency band and lower pressure drop than the commercial silencer at the same length. Nevertheless, the performance of the new silencer at high frequency band is not so satisfactory as to meet with the requirement. Therefore, a combination of the commercial silencer and the new reactive silencer will serve the ideal and an alternative solution to optimize the acoustic performance and minimise the energy consumption of the system.
Rights: All rights reserved
Access: restricted access

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