Measuring the degree of diffuseness of a sound field is crucial in many modern parametric spatial audio techniques. In these applications, intensity-based diffuseness estimators are particularly convenient, as the sound intensity can also be used to obtain, e.g., the direction of arrival of the sound. This contribution reviews different diffuseness estimators comparing them under the conditions found in practice, i.e., with arrays of noisy microphones and with the expectation operators substituted by finite temporal averages. The estimators show a similar performance, however, each with specific advantages and disadvantages depending on the scenario. Furthermore, the paper derives an estimator and highlights the possibility of using spatial averaging to improve the temporal resolution of the estimates.
while interaural coherence (IC) is perceived correctly, if the diffuseness is reproduced accurately. On the reproduction side, the acMultichannel sound systems become more and more established in tual signals of the loudspeaker channels are determined as a funcmodern audio applications. Consequently, the recording and the retion of these parameters so that an accurate spatial rendering can be production of spatial audio gains increasing attention. Directional achieved at a desired listening position.Audio Coding (DirAC) represents an efficient approach to analyze Note that there are substantial differences between DirAC and spatial sound and to reproduce it using arbitrary loudspeaker conparametric multichannel audio coding, such as MPEG Surround [5], figurations. In DirAC, the direction-of-arrival and the diffuseness although they share very similar processing structures. While MPEG of sound within frequency subbands is used to encode the spatial Surround is based on a time/frequency analysis of the different loudproperties of the observed sound field. The estimation of these paspeaker channels, DirAC takes microphone channels as input. Thus, rameters is based on an energetic sound field analysis using threeDirAC also represents an efficient recording technique for spatial dimensional microphone arrays. In practice, however, physical deaudio.sign constraints make three-dimensional microphone configurationsIn DirAC, the desired parameters are estimated via an energetic often not acceptable. In this paper, we consider a new approach to analysis of the sound field. This can be achieved by using B-format microphone array processing that allows for an estimation of both microphone signals [2], i.e., an omnidirectional signal and the sigdirection-of-arrival of sound and diffuseness based on planar micronals of three figure-of-eight microphones aligned with the axes of phone configurations. The performance of the proposed method is a Cartesian coordinate system. These signals can be directly meaevaluated via simulations and real measured data. sured using SoundField microphones [2] which are, however, far Index Terms-Spatial audio, microphone arrays too expensive for commercial consumer applications. Alternatively, three-dimensional (3D) microphone arrays can be used to generate the required B-format signals [6], where, e.g., six omnidirectional
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