抄録
This report describes the effects of the geometric parameters on the characteristics of secondary noise generated by the airflow in silencers constructed with a single expansion chamber. The peak values occur, regardless of the tailpipe resonance, on a noise spectrum measured for each chamber whose length lc is smaller than four times of the duct diameter d. The frequency fp at which a peak is highest may be predicted by Strouhal numbers (fp·lc/V, V : mean flow velocity) arranged as a function of lc/d. The overall noise levels computed by using individual spectra obtained for many chambers are dependent on the geometric factors when lc/d lies between 2.5 and 6, but reduce with the decreasing area expansion ratio and the increasing camber length in the range 6<lc/d<20.
