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Enhanced direction estimation using microphone arrays for directional audio coding

: Kallinger, M.; Kuech, F.; Schultz-Amling, R.; Galdo, G. del; Ahonen, J.; Pulkki, V.


Institute of Electrical and Electronics Engineers -IEEE-:
HSCMA 2008, Joint Workshop on Hands-free Speech Communication and Microphone Arrays : Trento - Italy, 6-8 May 2008
Piscataway, NJ: IEEE, 2008
ISBN: 978-1-4244-2337-8
ISBN: 978-1-4244-2338-5
Joint Workshop on Hands-Free Speech Communication and Microphone Arrays (HSCMA) <2008, Trento>
Conference Paper
Fraunhofer IIS ()

Modern home entertainment systems offer surround sound audio playback. This progress over known mono and stereo devices is also intended for high quality hands-free telephony to enhance intelligibility of speech in group conversation. Directional Audio Coding (DirAC) provides an efficient and well-established way to record and encode spatial sound and to render it at an arbitrary loudspeaker setup. On the recording site, DirAC is based on B-format microphone signals. These signals can be obtained by one omnidirectional and three figure-of-eight microphones pointing along the axes of a three-dimensional Cartesian coordinate system. However, a grid of omnidirectional microphones is more appropriate for consumer applications due to economic reasons. Arrays can provide the required figure-of-eight directionality only for a certain frequency range. However, in this contribution we show that a straightforward direction estimator is biased. After formulating the bias analytically we propose an unbiased estimator and derive the theoretical limits for unique direction estimation. The results are illustrated by means of simulations and measurements.