  Characterizing sound field diffuseness has many practical applications, from
room acoustics analysis to speech enhancement and sound field reproduction. In
this paper we investigate how spherical microphone arrays (SMAs) can be used to
characterize diffuseness. Due to their specific geometry, SMAs are particularly
well suited for analyzing the spatial properties of sound fields. In
particular, the signals recorded by an SMA can be analyzed in the spherical
harmonic (SH) domain, which has special and desirable mathematical properties
when it comes to analyzing diffuse sound fields. We present a new measure of
diffuseness, the COMEDIE diffuseness estimate, which is based on the analysis
of the SH signal covariance matrix. This algorithm is suited for the estimation
of diffuseness arising either from the presence of multiple sources distributed
around the SMA or from the presence of a diffuse noise background. As well, we
introduce the concept of a diffuseness profile, which consists in measuring the
diffuseness for several SH orders simultaneously. Experimental results indicate
that diffuseness profiles better describe the properties of the sound field
than a single diffuseness measurement.
