Oldenburg Branch Hearing, Speech and Audio Technology HSA

Audio Lab

© Fraunhofer IDMT

The audio laboratory of the Oldenburg Branch for Hearing, Speech and Audio Technology HSA offers many opportunities in the field of testing and developing audio products. The focus is on compact loudspeaker and microphone systems as well as voice-controlled devices. The facility offers standard living room acoustics for testing products under everyday conditions, such as at the end customer's home. This is particularly important for speech recognition systems.

If required, larger, more reverberant rooms can be realistically simulated using artificial, electro-acoustic reverberation. In addition, there is an anechoic cabin (internal dimensions LxWxH 220x14x230cm) for measurements in which the room influence should be as low as possible, such as for the acoustic characterization of microphones or loudspeakers.


  • Electroacoustic measurements on microphones, loudspeakers and audio products
    • Frequency response (electrical/acoustic)
    • Noise (electrical/acoustic)
    • Maximum sound pressure; power handling after distortion, electrical and mechanical destruction
    • Loudspeaker parameters: Linear (e.g. TSP), non-linear (various distortions)
    • Dispersion characteristics
    • Digital microphones: I2S, PDMT
    • Speech recognition systems (FAR, FRR) according to standard and customer-specific test setups
  • Structure-borne sound measurement via acceleration measurement or 1D laser
  • Audio recordings

Audiometric Booths

A total of nine acoustic measuring booths with a size of 3 to 29 m2 are available to the Institute for acoustic analysis. In addition to psychoacoustic fundamental research, the booths can also be used for measuring standard-audiometric parameters as well as complex free range setups and ERA/OAE devices.

© Fraunhofer IDMT
Audiometric Booth at the House of Hearing
© Hoertech gGmbH

Anechoic Room

Anechoic Room

Because of its size, equipment and frequency characteristic our anechoic room is ideally suited for precise acoustic measurements and psycho-acoustic tests. Additional Equipment is available for accurate sound-source localization experiments.

  • lower cut-off frequency 50 Hz
  • level of background noise lower than hearing threshold
  • spring supported absorber wedges (1.5 m long) to avoid frequency vibrations of 5 Hz and higher
  • Equipped for multi-channel playout and audio recording


Communication Acoustics Simulator

© Hoertech gGmbH

With the unique Communication Acoustics Simulator the acoustics of nearly every listening room can be simulated. The acoustic parameters of this room – reverb time and acoustic room size – can be changed and virtual sound sources can be placed inside. This way, acoustic characteristics of office buildings, cathedrals, concert halls and even train stations and bathrooms can be simulated. The room can be used for research projects that require definite, variable acoustic room characteristics and specific background noise situations.

  • 93 m2
  • electronic acoustic VRAS (Variable Room Acoustic System) for generating different reverberation and early reflection patterns
    variably set reverberation time of approx. 0.4 s to 6 s
  • Audiosignal matrix (LCS) with special DSP hard- and software
  • 16 microphones fixed invisibly to the ceiling
  • 24 loudspeaker channels (12 for reverberation, 12 for early reflection)
  • Subwoofer for low-frequency extension and for dolby surround input in VRAS
  • 8 input channels for surround noise scenarios and dolby surround performances
  • Connectors and patch fields for temporary microphones and loudspeakers
  • Audiovisual media equipment
  • Induction system for the hearing impaired


Equipment for User Studies

  • Video lab with one-way window
  • Eye tracking recorders
  • Neurophysiological measurements of cognitive stress by electroencephalography (EEG)
    •    mobile, wireless 24-channel EEG
  • Neuropsychological test batteries for testing hearing capability, memory and executive functions
© Fraunhofer IDMT/Tobias Trapp
Evaluation Study
© Fraunhofer IDMT/Tobias Trapp
User-Centered Design
© Fraunhofer IDMT/Daniel Schmidt
EEG Study

Prototyping Workshop

© Fraunhofer IDMT/Hannes Kalter

The workshop of the Fraunhofer IDMT in Oldenburg is suitable for the implementation of designs in the form of prototypes. The "Audio System Technology", "Automatic Speech Recognition" and "Acoustic Event Detection" groups in particular build and test prototypes here.

Two 3D printers, soldering workstations and other technical equipment are available for this purpose. The areas of application for the developed systems are in the fields of smart home, health and care or, for example, in human-technology interaction.

  • Two 3D printers
  • soldering equipment
  • Column drilling machine
  • flex
  • saw
  • milling machine
  • Workbenches


© Fraunhofer IDMT

Showroom and study lab with home environment

The Sound Technologies Lab at the Fraunhofer IDMT is both a showroom and a study laboratory, set up as a living and home office environment. Here, scientists can integrate newly developed technologies from the fields of acoustic event detection and speech and event recognition into concrete application scenarios. The laboratory also offers the opportunity to evaluate the technologies and their operating concepts together with partners from industry and research. For example, voice assistants for smart speakers could be tested in the living environment. This provides a comprehensive insight into research in the field of intelligent voice assistants.

In addition, the Sound Technologies Lab is certified in accordance with DIN 18041 "Audibility in small to medium-sized rooms" and is therefore ideally suited as an environment for evaluation and user studies.

VR Lab

© Fraunhofer IDMT

The VR laboratory at the University of Oldenburg is a specialized lab for reproducing (virtual) 3-D sound fields and is mainly used by the Fraunhofer IDMT for listening tests regarding localization abilities and technical measurements

  • 3-dimensional 86-channel loudspeaker system with 48 loudspeakers on a horizontal ring (diameter approx. 4.8 m)
  • 12, 6 and 1 loudspeaker each at ± 30, 60 and 90 degrees elevation
  • The surrounding room is semi-anechoic and equipped with 75 cm foam wedges.
  • A (removable) cylindrical screen for 180-degree video projection or head-mounted displays for visual presentations can be used.

Wind Tunnel

Fraunhofer IDMT uses the wind tunnel of the Oldenburg University to analyze influences of air flow on audio systems, e. g. on multimedia and communication devices worn at ones body.


  • Construction type: open measuring section, closed circuit; "Göttingen Type"
  • Speed: max. 50 m/s
  • Intensity of turbulence: under 0.3 %
  • Beam width: 1.0 m x 0.8 m
  • Drive: Radial fan with DC motor 77 kW
  • Flow measuring technology: 2D laser Doppler anemometer (LDA), hot wire anemometer, miniature-fan anemometer, acoustic turbulence probes, particle-image-velocimetry (PIV)
  • Acoustic measurement equipment: directional microphone array; in-flow measurements with flow microphones; correlation procedures for pseudo sound suppression