Abstract: The Hehnholtz resonator with a conical neck, which have broad acoustic attenuation band performance in the low frequency range, have no accurate analytical approach for the acoustic performance prediction. To investigate its acoustic performance, a general theory model based on the one-dimensional analysis approach with acoustic length corrections is developed to predict the transmission loss (TL). A segmentation method is used to calculate the acoustic correction lengths for the sound propagation in the conical tube. And then, an approximate formula is provided to give correction lengths for conical tubes with different geometries. The TL results obtained by the general theory and the acoustic correction lengths are compared with the results from the finite element method and experiment, which show that the deviations of the resonance frequency are less than 2 Hz and experiment, which show that the deviations of the resonance frequency are less than 2 Hz and much better than the results from one-dimensional approach without corrections. The method of the acoustic length correction for the conical neck, greatly improved the accuracy of the one-dimensional analysis approach, which will be quick and accurate to predict the sound attenuation property of the Helmholtz resonator with a conical neck.