Date of this Version
Malushte, H. (2013). Evaluation of SEA for Prediction of Breakout Noise from Air Duct, University of Nebraska-Lincoln.
The breakout noise from an air-conditioning duct is of immense concern in order to maintain a sound environment at home, office spaces, hospitals, etc. The challenge lies in correctly estimating the breakout noise by knowing the breakout sound transmission loss from the air duct. The ASHRAE Handbook: HVAC Applications (ASHRAE, 2011) currently lists some of theoretical transmission loss values for limited duct dimensions and gages (duct-wall thickness) at the octave band frequencies. Statistical Energy Analysis (SEA) is promising to predict the sound transmission loss for breakout noise for any given air duct configuration, particularly at high frequency. Though there are deterministic approaches such as finite element method (FEM) and boundary element method (BEM), they are unable to yield results efficiently for high frequency, while they also demand long computational time and memory. SEA on the contrary saves the computational effort and thus computational time. In this study, theoretical transmission loss of random duct configuration is selected from ASHRAE Handbook: HVAC Applications (ASHRAE, 2011) to evaluate the SEA method for correctly predicting the breakout sound transmission noise. All the applicable parameters for implementing SEA on a duct are discussed and the method is then simulated. The predicted results are then compared with the theoretical results (ASHRAE, 2011). Initially, there are some discrepancies between the predicted results by SEA and the theoretical results in transmission loss observed at higher frequencies. Further investigation leads to a formulation of a factor that is applied to the conventional SEA approach. The predicted results from the new formulation show a close agreement with the existing theoretical results and are mostly within 3 dB difference. The SEA predictions are also compared with the experimental data (Cummings 1983) to establish SEA’s validity. The SEA predicted results are also found to be close with the experimental results for the all the duct configurations and maintain agreement mostly within 3 dB.
Advisor: Siu-Kit Lau