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Testing Acoustic Materials in an Impedance Tube

Black impedance tubes with microphones attached and m+p VibPilot front-end
Impedance tube testing using two or four microphones

Sound quality is becoming increasingly important in product design. Constructive measures and acoustic materials serve to reduce or optimize the perceived noise of a product in the context of sound design. The sound characteristics of such materials can be identified with impedance tubes in the laboratory under controlled conditions.

With the optional Impedance Tube Testing software package, m+p Analyzer allows the calculation of important characteristics of acoustic materials such as absorption coefficient, reflection coefficient, impedance and transmission loss coefficients based on impedance tube measurements according to ISO 10534-2, ASTM E1050-12 or ASTM E2611-17.

Impedance tube with microphones attached laptop m+p VibPilot front-end
Impedance tube testing using m+p Analyzer software and m+p VibPilot front-end

Depending on the test standard, measurements are taken using either two or four microphones. The latter method allows the transmission loss to be calculated, as two microphones are placed on each side of the test object. The software package assists in determining the loudspeaker volume for the required signal-to-noise ratio by using pre-test measurements to establish the calibration coefficients for microphone mismatch correction. The measurement results are displayed online and the desired acoustic coefficients are calculated. Of course, all results can be summarized in a report containing the test setup, results and specific information according to the applied test standard.

Screenshot showing impedance tube test set-up and data
Test set-up

Scope of supply:
- Impedance tube (incl. loudspeaker, tube, sample holder, cables)
- Power amplifier
- 2 or 4 microphones and a sound calibrator
- Measurement front-end (e.g. 4-channel m+p VibPilot)
- m+p Analyzer DSAstd + impedance tube (AN-IMP)

Read more in the brochure “m+p Impedance Tube Solutions”.


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