A one-dimensional wave model for numerical analyses ofventilation openings with Helmholtz resonator attachments

摘要

A ventilation opening becomes a primary sound transmission path for a room when the room employs double glazing windows for sound insulation. Especially it is difficult to suppressthe noise component that coincides with the lowest resonance frequency of the longitudinal modes ofthe opening. For this mode, Helmholtz resonator attachments can be effective while mufflers made ofsound absorbing materials work only a little. However in designing a Helmholtz resonator attachmentto a ventilation opening, a series of trial and error simulations are indispensable because resonatorshave reactive nature. Numerical analyses based on one-dimensional wave models are preferable forthe repetitious optimal design stage. However, for a resonator array of very short longitudinal intervalsof a few centimeters, effectiveness of one-dimensional wave models has not been confirmed so far.Several prototypes of Helmholtz resonator attachments were investigated here. Their performances were determined by conducting experimental tests, numerical simulations by a one-dimensional plane wave model and those by a three-dimensional BEM. Consequently, for an transmission loss curve (for 100 discrete frequencies) of an opening of less than a half meter long, the numerical analysis by the three-dimensional BEM took a week while that by the one-dimensional plane wave model performed instantaneously. Nevertheless the results by the one-dimensional wave model agree excellently with those by the three-dimensional BEM, and agree fairly well with those by the experiments.