Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2009, Article ID 298605, 10 pages doi:10.1155/2009/298605 Research Article Database of Multichannel In-Ear and Behind-the-Ear Head-Related and Binaural Room Impulse Responses H. Kayser, S. D. Ewert, J. Anem¨ uller, T. Rohdenburg, V. Hohmann, and B. Kollmeier Medizinische Physik, Universit¨ at Oldenburg, 26111 Oldenburg, Germany Correspondence should be addressed to H. Kayser, hendrik.kayser@uni-oldenburg.de Received 15 December 2008; Accepted 4 June 2009 Recommended by Hugo Fastl An eight-channel database of head-related impulse responses (HRIRs) and binaural room impulse responses (BRIRs) is introduced. The impulse responses (IRs) were measured with three-channel behind-the-ear (BTEs) hearing aids and an in-ear microphone at both ears of a human head and torso simulator. The database aims at providing a tool for the evaluation of multichannel hearing aid algorithms in hearing aid research. In addition to the HRIRs derived from measurements in an anechoic chamber, sets of BRIRs for multiple, realistic head and sound-source positions in four natural environments reflecting daily- life communication situations with different reverberation times are provided. For comparison, analytically derived IRs for a rigid acoustic sphere were computed at the multichannel microphone positions of the BTEs and differences to real HRIRs were examined. The scenes’ natural acoustic background was also recorded in each of the real-world environments for all eight channels. Overall, the present database allows for a realistic construction of simulated sound fields for hearing instrument research and, consequently, for a realistic evaluation of hearing instrument algorithms. Copyright © 2009 H. Kayser et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1. Introduction Performance evaluation is an important part of hearing instrument algorithm research since only a careful evaluation of accomplished effects can identify truly promising and successful signal enhancement methods. The gold standard for evaluation will always be the unconstrained real-world environment, which comes however at a relatively high cost in terms of time and effort for performance comparisons. Simulation approaches to the evaluation task are the first steps in identifying good signal processing algorithms. It is therefore important to utilize simulated input signals that represent real-world signals as faithfully as possible, especially if multimicrophone arrays and binaural hearing instrument algorithms are considered that expect input from both sides of a listener’s head. The simplest approach to model the input signals to a multichannel or binaural hearing instrument is the free-field model. More elaborate models are based on analytical formulations of the effect that a rigid sphere has on the acoustic field [1, 2]. Finally, the synthetic generation of multichannel input signals by means of convolving recorded (single-channel) sound signals with impulse responses (IRs) corresponding to the respective spatial sound source positions, and also depending on the spatial microphone locations, represents a good approximation to the expected recordings from a real- world sound field. It comes at a fraction of the cost and with virtually unlimited flexibility in arranging different acoustic objects at various locations in virtual acoustic space if the appropriate room-, head-, and microphone-related impulse responses are available. In addition, when recordings from multichannel hearing aids and in-ear microphones in a real acoustic background sound field are available, even more realistic situations can be produced by superimposing convolved contributions from localized sound sources with the approximately omnidirec- tional real sound field recording at a predefined mixing ratio. By this means, the level of disturbing background noise can be controlled independently from the localized sound sources. Under the assumption of a linear and time-invariant propagation of sound from a fixed source to a receiver, the impulse response completely describes the system. All transmission characteristics of the environment and objects