Method to resolve microphone and sample location errors in the two-microphone duct measurement method
- 1 November 2000
- journal article
- Published by Acoustical Society of America (ASA) in The Journal of the Acoustical Society of America
- Vol. 108 (5), 2231-2237
- https://doi.org/10.1121/1.1314318
Abstract
Utilizing the two-microphone impedance tube method, the normal incidence acoustic absorption and acoustic impedance can be measured for a given sample. This method relies on the measured transfer function between two microphones, and the knowledge of their precise location relative to each other and the sample material. In this article, a method is proposed to accurately determine these locations. A third sensor is added at the end of the tube to simplify the measurement. First, a justification and investigation of the method is presented. Second, reference terminations are measured to evaluate the accuracy of the apparatus. Finally, comparisons are made between the new method and current methods for determining these distances and the variations are discussed. From this, conclusions are drawn with regards to the applicability and need for the new method and under which circumstances it is applicable. Results show that the method provides a reliable determination of both microphone locations, which is not possible using the current techniques. Errors due to inaccurate determinination of these parameters between methods were on the order of 3% for R and 12% for Re Z.Keywords
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