Investigation of errors and uncertainty in low-frequency impedance tube measurements

Abstract

The accuracy of impedance tube measurements can be improved by determining the acoustic conditions within the impedance tube prior to introducing a sample for test. By measuring the empty impedance tube, the influence of environmental changes on the critical parameters can be minimized. The low-frequency dissipation is estimated using Bayesian inference to incorporate into a transfer function model, reducing error when measuring samples. Previous work [Chen & Xiang, J. Acoust. Soc. Am., 155, 2646–2658 (2024)] has focused on a frequency range of 1.5–5 kHz; the subject of this study is a lower frequency range (<1.5 kHz) using larger sized impedance tubes. This talk details the methodology and results of the study, its inclusion within an updated transfer function model, the accuracy of the model, recommendations for improved impedance tube measurement procedures, and next steps.