Impedance & transmission tube using 3 microphones
Mecanum’s 3 microphones impedance and transmission tubes are specifically designed to measure the main normal indicators of a wide range of acoustical materials. The method is based on ASTM E1050 and ISO 10534-2 standards for the absorption coefficient (α), the reflection coefficient (R) and the surface impedance (Zs). All other indicators are determined using the 3 microphones technique12 which uses equations of ASTM E2611. The 3 microphones technique is an improvement of the ASTM E2611 where unknown termination loads are replaced by known cavities. The third microphone is inserted in the piston and always exposed to a maximum pressure for a better signal to noise ratio.
** Large spacing between µ1 and µ2 is essential for better results at low frequencies (as stated in ASTM E1050)
*** µ3 is built in the termination
➡ Transfer matrix coefficients (Tij)
|Tube Internal Diameter||Frequency Range|
|29 mm||200-6600 Hz|
|44.44 mm||100-4300 Hz|
|100 mm||35-1900 Hz|
Tube-X is a user-friendly software that will simplify the measurement procedure. It’s also fully compatible with Foam-X software that can extract non-acoustic parameters of porous materials using the inverse method with a 2 microphones absorption measurement and the indirect method using the 3 microphones measurement.
- Every Mecanum impedance tube is supplied with grids (for samples with low mechanical strength) and rings (to avoid leaks).
- Different accessories may be used with impedance tubes according to your needs.