Experimental study on open-end correction of a Helmholtz resonator narrow slit neck

In general, the acoustic effective length of the open end of an air column is longer than its geometric length. Here, the effective increment of the geometric length of an air column is called the open-end correction length, which is an acoustically crucial issue. The purpose of this study is to experimentally clarify the open-end correction length for a slit shape with a narrow clearance. For this reason, the sound absorption coefficient was measured using a sample in which the neck of the Helmholtz resonator was shaped as a slit with a narrow clearance. Next, the open-end correction length (i.e., mass end correction length and resistive end correction length) was calculated backward by comparing the experimental and theoretical sound absorption curves. The resistive end correction increased as the slit width became narrower within the range of 0.5 mm or less for both the center slit and the slit near the wall, indicating a significant discrepancy between the theoretical equation and the estimated value. For the mass end correction, in the case the center slit, the estimated value is close to the theoretical value of in the slit width range from 0.3 mm to 1.0 mm. The results of this study may be useful in eliminating discrepancies in correction values for open-end correction in slits with narrow clearance. © 2022 Institute of Noise Control Engineering.