The Kundt tube, also known as Impedance tube is an instrument that is used to easily testing sound absorption and transmission loss without having to go to a huge anechoic room.

The SW series Impedance Tubes can accurately measure sound absorption coefficients
and impedance according to both ISO and ASTM standards. They also support the sound
transmission loss measurements based on the Transfer Function Method. The Transfer
Function Method separates the incident and reflected energy from the measured transfer
function, and then estimates the acoustic properties of the tested sample installed in the
tube.


The SW series Impedance Tubes are specially designed not only to work with the cut
samples but also for direct use in the field. The small size and durable aluminum
construction make it easy to be transported and used for estimating the properties of walls,
ceilings, installed building materials, road surfaces, different ground surfaces, interiors of
vehicles, etc. Geonoise offers the complete set of the Impedance Tube system, which includes:
the tubes, microphones; DAQ hardware and measurement software.


The 1/4’’ microphones MPA416, which have excellent phase matches, are ideal for
impedance applications. The microphones are directly connected to optional 2-channel
MC3522 or 4-channel MC3242 data acquisition hardware. The PA50 power amplifier is used to
drive the loudspeaker in the impedance tube. The VA-Lab software provides all
measurement functions for sound absorption and transmission loss testing.

The standards used are:

  • sound absorption, ISO10534-2, ASTM E1050
  • transmission loss, ASTM E2611

This is a typical setup of the measurement equipment:

Impedance Tube schematic

Please contact us for the various setup’s for measuring sound absorption and/or transmission loss such as SW230 SW260, SW420, SW470, SW477.

Geonoise Impedance Tube datasheet