Laboratory Sound Transmission Loss Testing

Building Acoustics

Laboratory Sound Transmission Testing

SINUS Soundbook/Apollo Devices + Impedance tube + AFD software


The impedance tube AFD 1000 – AcoustiTube® measurement system determines the sound absorption and reflection coefficients as well as the impedance ratio of material samples in a laboratory based on the DIN EN ISO 10534-2 transfer-factor method.

The measurement results allow direct retrieval of the rated sound absorption coefficient of the sample according to DIN EN ISO 11654.

AcoustiTube is based on a measurement technique in which a plane sound wave is emitted against a sound-absorbing material sample in front of a reverberant termination within the impedance tube. The resulting sound pressure is measured by two microphones in front of the sample. The two microphones are connected to a SINUS Apollo Box or SoundBook and the AFD software is used to communicate with the acquisition device and perform the measurements.

The extension of the impedance tube to make a transmission tube (AFD 1000 plus AFD 1401 analysis software) allows determination of sound insulation values, the transmission coefficient, the complex impedance and the complex wave number (absorber parameter) by applying Song’s and Bolton’s transfer-matrix method. Using the obtained measurement results the insertion loss and the diffuse sound absorption coefficient (compared to measurements in a reverberation chamber according to DIN EN ISO 354) may be predicted directly.

Sample holders

Depending on the application field different sample holders are available.

Sample holder I

Application field: Determination of the sound absorption coefficient in a laboratory according to DIN EN ISO 10534-2.

Samples: Cylindrical samples with a diameter of 15mm, 30mm, 40mm or 100mm.

Application: Mounting and soundproof sealing of prepared cylindrical samples of variable thickness on continuously adjustable and lockable sample holder. 

Sample holder II

Application field: In-situ determination of the sound absorption coefficient according to DIN ISO 13472-2 (sound absorption coefficient < 0.15).

For samples of road surfaces and plate-shaped samples with minimum dimensions of 300mm x 300mm

Adapter for soundproof attachment of the impedance tube to a sample surface.

Compression sample holder

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


AFD 1000.1 Impedance Tube Software

The AFD 1000 software is a comprehensive, high-performance engineering tool for the frequency-dependent determination of material characteristics. AFD 1000 enables you to average the results from different material samples, to easily manage and compare results using a database and to determine the sound absorption and reflection coefficients as well as the impedance ratio of test objects in the laboratory based on the DIN EN ISO 10534-2 transfer-factor method.

AFD 1401 Software Transmission

The AFD 1401 software, when installed in addition to the AFD1000.1 software, allows the determination of the sound insulation, the transmission coefficient, the complex impedance, the complex wave number and the transmission loss of open porous cylindrical specimens in the laboratory on the basis of the Two-Load Method. Selected measurements of different microphone distances and different system diameters in the frequency range may be averaged in accordance with DIN EN ISO 10534-2 using the AFD 1401 Viewer.

AFD 3001 – Acoustic Design of Multi-Layer Systems

In addition, the AFD 3001 software allows the acoustic design of multilayer systems by means of a 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)

General technical specifications of AcoustiTube

15mm impedance tube

Inner diameter


Frequency range

150 … 10200Hz

30mm impedance tube

Inner diameter


Frequency range

150 … 6600Hz

40mm impedance tube

Inner diameter


Frequency range

100 … 4400Hz

100mm impedance tube

Inner diameter


Frequency range

50 … 2000Hz

Sample thickness

AFD 1000


AFD 1200


Compression sample holder


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