**Researchers**: Daniel Jarrett, Emanuël Habets, Mark Thomas, Patrick Naylor

**» Noise reduction in the spherical harmonic domain using a tradeoff beamformer and narrowband DOA estimates: Audio examples**

**» A tradeoff beamformer for noise reduction in the spherical harmonic domain: Audio examples**

While linear and planar microphone arrays have been the subject of much research, and are now relatively well understood, spherical microphone arrays, on the other hand, have only recently become a topic of interest. Their spherical symmetry facilitates three-dimensional analysis of the sound field.

Within the field of signal processing for spherical microphone arrays, this project has so far focused on two main contribution areas. The first is **2D direction of arrival** (azimuth and elevation) **estimation **[1] **and source tracking using eigenbeams** [2], a spatial decomposition of the sound field. Applications include automated camera steering and microphone array beamformer steering. The proposed method is shown to have good accuracy even in highly reverberant environments.

The second contribution area is **room impulse response simulation** [3]. This allows us to simulate the sound pressure signals on a spherical microphone array in a reverberant enclosure, taking into account the scattering introduced by a solid sphere. This is necessary to extensively test spherical array processing algorithms in the presence of reverberation, since tests with real measurements are expensive (due to the high cost of the arrays) and time-consuming.

**Relevant publications:**

- 3D Source Localization in the Spherical Harmonic Domain Using a Pseudointensity Vector. In: Proc. European Signal Processing Conf. (EUSIPCO), Aalborg, Denmark, 2010.
- Eigenbeam-based Acoustic Source Tracking in Noisy Reverberant Environments. In: Proc. Asilomar Conf. on Signals, Systems and Computers, Pacific Grove, California, USA, 2010.
- Simulating Room Impulse Responses for Spherical Microphone Arrays. In: Proc. IEEE Intl. Conf. on Acoustics, Speech and Signal Processing (ICASSP), Prague, Czech Republic, 2011.
- Dereverberation Performance of Rigid and Open Spherical Microphone Arrays: Theory & Simulation. In: Proc. Joint Workshop on Hands-Free Speech Communication and Microphone Arrays (HSCMA), Edinburgh, UK, 2011.
- A tradeoff beamformer for noise reduction in the spherical harmonic domain. In: Proc. Intl. Workshop Acoust. Signal Enhancement (IWAENC), Aachen, Germany, 2012.
- Rigid sphere room impulse response simulation: algorithm and applications. In: Journal of the Acoustical Society of America, 132 (3), pp. 1462-1472, 2012.
- On the noise reduction performance of a spherical harmonic domain tradeoff beamformer. In: IEEE Signal Processing Letters, 19 (11), pp. 773-776, 2012.
- Coherence-based diffuseness estimation in the spherical harmonic domain. Proc. of the IEEE Convention of Electrical and Electronics Engineers in Israel (IEEEI), 2012.
- Spherical harmonic domain noise reduction using an MVDR beamformer and DOA-based second-order statistics estimation. In: Proc. IEEE Intl. Conf. on Acoustics, Speech and Signal Processing (ICASSP), Vancouver, Canada, 2013.
- Noise reduction in the spherical harmonic domain using a tradeoff beamformer and narrowband DOA estimates. In: IEEE/ACM Trans. Audio, Speech, Lang. Process., 22 (5), pp. 965-976, 2014.
- Theory and Applications of Spherical Microphone Array Processing. Springer International Publishing, 2016.