  The ability to accurately estimate room impulse responses (RIRs) is integral
to many applications of spatial audio processing. Regrettably, estimating the
RIR using ambient signals, such as speech or music, remains a challenging
problem due to, e.g., low signal-to-noise ratios, finite sample lengths, and
poor spectral excitation. Commonly, in order to improve the conditioning of the
estimation problem, priors are placed on the amplitudes of the RIR. Although
serving as a regularizer, this type of prior is generally not useful when only
approximate knowledge of the delay structure is available, which, for example,
is the case when the prior is a simulated RIR from an approximation of the room
geometry. In this work, we target the delay structure itself, constructing a
prior based on the concept of optimal transport. As illustrated using both
simulated and measured data, the resulting method is able to beneficially
incorporate information even from simple simulation models, displaying
considerable robustness to perturbations in the assumed room dimensions and its
temperature.
