IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 60, NO. 4, APRIL 2011 1141 Instantaneous Binaural Target PSD Estimation for Hearing Aid Noise Reduction in Complex Acoustic Environments A. Homayoun Kamkar-Parsi and Martin Bouchard Abstract—Some hearing aid models such as the in-the-ear or in-the-canal model are small, and due to size constraints, only a single microphone per hearing aid can be fitted. As a result, only the single-channel noise reduction schemes can be integrated in them. However, in the near future, binaural hearing aids will be available. These hearing aids will allow hearing devices on each side of the head to receive information from the micro- phones located on both devices via a wireless link. This addi- tional information allows the use of joint statistics and/or spatial information, which allows the use of better denoising methods. The main contribution of this paper is to introduce a binaural target power spectral density (PSD) estimator for binaural hearing aids under the presence of a background interfering talker (or a lateral transient noise). This paper then presents an example of how the proposed target PSD estimator and another recently developed binaural diffuse noise PSD estimator can be integrated to produce a binaural noise reduction scheme that can operate in real-life complex acoustic environments that are composed of time-varying diffuse noise, multiple directional nonstationary talkers (or noises), and reverberant conditions. Such a binaural noise reduction system allows the substantial reduction of different combinations of diverse background noises and the increase in speech intelligibility while guaranteeing the preservation of the interaural cues of both the target speech and the directional back- ground noises. A comparison with several advanced denoising al- gorithms is made in this paper by using several objective measures and real-life hearing aid signals, showing the good performance of the example binaural noise reduction scheme that uses the proposed PSD estimator. Index Terms—Binaural estimators, binaural hearing aids, interaural cues preservation, nonstationary noise reduction, speech enhancement, target power spectrum density (PSD) estimation. I. I NTRODUCTION F OR HEARING aid devices with two or more microphones, the microphone array technology can provide great ben- efits. The microphones can be configured in a small endfire Manuscript received December 16, 2009; revised May 27, 2010; accepted August 25, 2010. Date of publication November 1, 2010; date of current version March 8, 2011. This work was supported in part by a Natural Sciences and Engineering Research Council of Canada (NSERC) student scholarship and in part by an NSERC-CRD research grant. The Associate Editor coordinating the review process for this paper was Dr. Jiong Tang. A. H. Kamkar-Parsi is with the Siemens Audiologische Technik GmbH, 91058 Erlangen, Germany (e-mail: hkamkarparsi@gmail.com). M. Bouchard is with the School of Information Technology and Engineering, University of Ottawa, Ottawa, ON K1N 6N5, Canada (e-mail: bouchard@ site.uottawa.ca). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIM.2010.2084690 array, which allows the implementation of classical beamform- ing schemes. Speech enhancement or denoising using beam- forming takes advantage of the spatial diversity of the target speech and noise sources by altering and combining multiple noisy input microphone signals in a way that can significantly reduce background noise and increase speech intelligibility. Unfortunately, due to size constraints, only certain hearing device models such as behind-the-ear (BTE) can accommodate two or occasionally three microphones. Smaller models such as the in-the-canal (ITC) or in-the-ear model only permit the fitting of a single microphone. Consequently, beamforming cannot be used for such cases, and so far, only the single- channel noise reduction schemes could be used (i.e., with a single microphone per hearing device). These single-channel noise reduction schemes are less effective since the spatial information cannot be exploited, and they also tend to introduce some speech distortion or musical noise, especially if the noise reduction is aggressive. In the near future, new types of high-end hearing aids such as binaural hearing aids will be available. In the current bilateral hearing aids, a hearing-impaired person wears a hearing aid on each ear, and each hearing aid processes only its own micro- phone input. Unlike these current systems, the new binaural hearing aids will allow hearing devices on each side of the head to receive information from the microphone located on both devices via a wireless link. As a result, working with a binaural system, new classes of noise reduction schemes as well as new power spectrum density (PSD) estimation techniques can be developed [1]. The previous few attempts to include binaural processing in hearing aid noise reduction algorithms have not fully achieved a significant improvement in performance under difficult practical situations. In [2] (which complements the work in [3] and several related publications such as [4] and [5]), a binaural multichannel Wiener filter (MWF) technique with a modified cost function was developed to essentially reduce directional noise while having some control over the distortion level of the binaural interaural cues for the target speech and noise components. A good performance for the MWF was reported for the case of a single directional noise in the background [2]. However, the directional background noise is restrained to be stationary or slowly fluctuating for the MWF to perform well, and the noise source should not relocate during target speech activity since its characteristics are only computed during target speech pauses. In addition, for cases where the directional noise is speech or when there are 0018-9456/$26.00 © 2010 IEEE