1060 Rue Cherbourg, Sherbrooke, J1K2N8, Canada

(819) 346-5666 info@mecanum.com

Impedance and transmission tube (3 mic)

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.

Tube_2mic_scheme_3dTube_3mic_scheme_3d

**  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

Material properties

➡ Normal incidence sound absorption coefficient (α)

➡ Normal incidence complex reflection coefficient (R)

➡ Normal surface impedance (Zs/Zair)

➡ Normal incidence sound transmission loss (TL)

➡ Characteristic impedance (Z/Zair)

➡ Wave number (k)

➡ Transfer matrix coefficients (Tij)

➡ Equivalent/effective dynamic density (ρeq)

➡ Equivalent/effective dynamic bulk modulus or compressibility (Keq)

TUBE SPECIFICATIONS

Tube Internal Diameter Frequency Range
29 mm  200-6600 Hz
44.44 mm 100-4300 Hz
 100 mm 35-1900 Hz

TUBE-X SOFTWARE

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.

ADDITIONAL INFORMATION

  • 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.