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Audio Communication GroupF.A.B.I.A.N. - Fast and Automatic Binaural Impulse response AcquisitioN

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F.A.B.I.A.N. - Fast and Automatic Binaural Impulse response AcquisitioN



Description of the project

The Artificial Head-Torso-Simulator F.A.B.I.A.N. (Fast and Automatic Binaural Impulse response AcquisitioN, [1], [2]), developed by the Audio Communication Group serves for the measurement of so-called binaural room impulse responses (BRIRs, or binaural room transfer functions, BRTFs). These BRIRs describe the transmission of the sound from a sound source in a hall to the ears of a listener. Usually, loudspeakers are used as sound sources, whereas sine sweeps - as can be heard in the above video - may be used as measurement signals.

When filtering anechoic recordings of arbitrary signals (e.g. a talker or a musical piece) with these BRIRs and listening to the result over headphones, an auditory impression will emerge to be actually located in the respective hall and to be listening to the talker or the musicians there (out-of-head localization). Additionally, if BRIRs have been measured for different head orientations of a listener, the anechoic audio signal can be filtered with the respective BRIR selected in real-time according to the head movements of a listener which are observed e.g. by using a head-tracker (so-called dynamic binaural synthesis [3]). In this case, the perceived realism will increase substantially. As opposed to the situation usually perceived with conventional headphone playback, virtual sound sources will now be perceived at stable locations outside one's head even while moving the head. Current research [4] shows, that a state of the art dynamic binaural simulation may achieve such a high degree of realism, that subjects cannot distinguish virtual sound sources from real ones anymore, while assessing either of them only with reference to their own experience.

The binaural measurement robot FABIAN allows to concurrently rotate an artificial human head horizontally and vertically above the torso using a servomotoric neck joint. Lateral rotational movements maybe provided after a minor mechanical modification. An additional rotary table allows rotating the torso as a whole, providing different alignments between head and shoulders. For measurements in seating position the torso can be used without the turntable and the supporting construction.

The neck joint allows for a very precise and fast positioning of the head, within a range of physiologically sensitive bounds (horizontal rotation within +-90°, vertical rotation from -45° to +90°). The torso was developed based on biometrical data and represents the median of the German population between the ages of 18-65, while the head itself und the outer ears are based on individual casts.

For the mechanical control and the acoustical measurements a special Matlab®-application has been developed.

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