Impedance tube, Kundt’s tube, sound absorption and transmission loss
The impedance tube (also know as Kundt Tube) measurement obtains the normal incidence absorption coefficient of a layer of textiles with a small diameter (usually less than 10 cm).
The results can be used to compare the basic absorption performance of the material and for acoustics simulations.
In practice, the absorbers can be quite large and their structure and configuration may be complex and part of acoustic designs. Furthermore, they will be exposed to real sound fields where the incident sound may come from many directions.
The PLACID impedance tube kit consists of 2 or 3 tubes with a diameter of 16, 30, and 100 mm to cover the whole frequency range. At the end of the tube, a loudspeaker is mounted and will emit a precisely quantified sound generated by the signal generator and amplified by the amplifier. The 4 channel Data Acquisition System (DAQ) will gather and record all measurement data and relay it to the software.
The microphones will measure the sound level at each given position. The software will then calculate the normal incident acoustic properties of the material based on the frequency response functions measured between the various measurement locations.
The Impedance tube kit can determine the sound absorption coefficient as well as the transmission loss.
PI8810, 100 mm impedance tube, frequency range 50 Hz – 1600 Hz
PI8803, 30 mm impedance tube, frequency range 800 – 6300 Hz
PI88016, 16mm impedance tube, frequency range 5000 – 10000 Hz
Impedance tube can measure sound absorption coefficient as well as transmission loss, ISO10543-2, ASTM E1050-08.
Microphones used: 1/4″ Class I or class II , 20 Hz to 20 kHz (BNC to SMB connector).
Applications for Impedance Tube
- testing of material characteristics and verifying material compliance before implementing the materials in the assemblies
- design of acoustic comfort in aircraft, helicopters, ships, yachts, and vehicle interiors by selecting the optimal acoustic treatments and noise barriers
- research and development of noise control products by benchmarking competitive products
- research jobs for students and universities
- validating and calibrating theoretical computational methods such as acoustic modeling
Define material Characteristics
Materials in an acoustic application typically either are used for sound absorption or for noise transmission loss. Acoustic designers need to know the exact noise characteristics of a material to be able to make predictions. Testing a material in the Impedance Tube is quick and precise.
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