The impedance tube AED 1000 – AcoustiTube® is a measuring system for determining the sound absorption coefficient, the sound reflection factor and the impedance ratio of materials in the laboratory on the basis of the transfer function method described in DIN EN ISO 10534-2, ASTM E1050 and DIN EN ISO 13472-2.

In the impedance tube a plain sound wave is generated and sent against a sound absorbing specimen in front of a reverberant termination. The resulting sound pressure is measured by using two microphones in front of the material sample. The sound absorption coefficient of the material is determined by evaluating the incoming and reflected sound energy.

Extension of Impedance Tube to Transmission Tube

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An extension of the impedance tube to the transmission tube allows the determination of the characteristic absorber values (wave number ka and characteristic impedance Za), the transmission coefficient and the sound insulation (transmission loss) by applying the Two-Load Method with 4 microphones according to ASTM E2611 (Transmission Matrix Method). On such basis, the insertion loss of mufflers (software for acoustic design of mufflers AcoustiCalc®-Silencer) and the diffuse sound absorption coefficient (software for acoustic design of sound absorbers AcoustiCalc® -Absorber), comparison to measurements in the reverberation chamber according to DIN EN ISO 354, especially rated sound absorption coefficient of the material according to DIN EN ISO 11654) can be computed directly.

Sample Holder

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Depending on the application field different sample holders are available.

Sample holder I

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• Application: determination of sound absorption coefficient of materials in the laboratory according to DIN EN ISO 10534-2 and ASTM E1050
• Specimens: cylindrical specimens with a diameter of 15 mm, 30 mm, 40 mm or 100 mm
• Method: prepared cylindrical specimens of variable thickness are mounted and sealed into the specimen holder, which can be continuously positioned and adjusted

Sample holder II

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• Application: determination of sound absorption coefficient in situ according to DIN ISO 13472-2 (sound absorption coefficient < 0,15)
• Specimens: road surfaces and plates of specimens with a dimension of at least 300 mm x 300 mm
• Method: adapter for tight attachment of impedance tube to the surface of the specimen

Compression sample holder

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The compression sample holder is an extension to the impedance and transmission tubes. It is almost continuously adjustable in length. Furthermore the compression sample holder allows defined compression of cylindrical samples or bulk sample material for determination of the sound absorption coefficient, sound insulation, absorber parameters and flow resistance. Finally it facilitates controlled installation of thin materials.

Options

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Software

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3001 – AcoustiCalc®-Absorber (Acoustic Design of Multi-Layer Systems) (802054.0)
Additionally the 3001 – AcoustiCalc®-Absorber1 software allows ther definition of multilayer system by means of graphical user interface.

Input parameters

• environmental conditions
• thickness of material setup
• material parameters, e. g. length-related airflow resistance; tortuosity; structure factor; porosity
• calculation models / measured data: Air and open porous absorbers. Model according to DELANY-BAZELY; model of homogeneous medium; phenomenological model; complex absorber values measured in the transmission tube (continuous spectrum)