One essential part in the development and research of algorithms for speech and audio applications is its evaluation with objective measures and subjective listening tests. Although, it is convenient to design such algorithms based on objective measures, cross-checks with extensive subjective tests are indispensable. These cross-checks may be integrated at different stages of the development cycle starting from the identification of the challenges related to a certain task until the verification of prototypes or live-demonstrations.
The AudioLab offers useful tools and high-end audio capturing as well as reproduction devices to facilitate listening tests and acoustic measurements in a controlled environment. It features an acoustically isolated sound booth with a reverberation time less than 0.1 s and an insulation of up to 50 dB. Experiments can be conducted from outside the sound booth. The hardware within the booth is connected via ADAT, S/PDIF and multi-core cables to a PC, which represents the heart of the setup.
Audio Hardware Components
An RME Hammerfall DSP Multiface II, connected through a PCI extension card to the measurement PC, serves as an audio interface. It allows for recording and playback of up to 18 symmetric channels at 24-bit/96 kHz. RME TotalMix performs a flexible signal routing and the volume control.
An RME Micstasy 8 channel pre-amp with a gain range of 85 dB extends the Multifaces analog input capabilities and is positioned in the studio box. For sound reproduction, four Nubert nuPro A-300 speakers are installed in the corners of the booth. This setup facilitates, e.g., the simulation of diffuse sound fields.
For listening tests, additionally a pair of Sennheiser HD600 headphones is connected through a HEAD acoustics PEQ V equalizer, yielding high-fidelity sound reproduction. The measurement PC is further equipped with a pair of Genelec 8130A speakers and headphone amplifiers for simultaneous monitoring over up to 9 headphones. A HEAD acoustics HMS II.3 dummy head as well as a LT 360 precision turntable are also available at the institute.