Murray, P., Kunio, J., Christensen, L., and Larsen, F., "Use of a Portable Flanged Impedance Tube for Absorber Design and Measurement," SAE Technical Paper 2015-01-2201, 2015, doi:10.4271/2015-01-2201.
Acoustic material testing is becoming increasingly relevant to engineers, designers and manufacturers from a broad range of industries. This paper presents comparisons between material absorption measurements made using the traditional approaches of the reverberation room method and the fixed impedance tube using a sample holder, with those obtained using a lightweight portable flanged impedance tube method.The portable tube allows fast non-destructive in-situ material measurements. It may therefore be used to measure the impact of the installed lay-up (e.g. effects of facing sheets, curvature, material compression, bagging, etc.).Results are presented for both non-locally reacting and locally reacting materials. The flanged tube results are compared directly with in-tube data. They are also corrected for random incidence to allow comparison with the diffuse field reverberation room data. It is concluded that the flanged portable impedance tube method provides an attractive alternative to existing methods.