arXiv:2610.31596v1 Announce Type: new Abstract: The nature of room impulse response signals is often adverse to a clear evaluation of similarity: they are sparse, rapidly varying, signed signals resulting from the complex interaction of room reflections and phase relationships. Therefore, conventional point-wise metrics may be sensitive to small temporal shifts and provide poor loss surfaces for optimization. In this paper, we propose an optimal transport-based distance for RIR similarity that explicitly accounts for the structure of impulse responses, inspired by the signed Wasserstein distance formulation. Optimal transport provides a natural framework for this problem, by comparing signals based on how their underlying distributions are displaced rather than requiring a one-to-one correspondence. We evaluate the proposed distance against commonly used audio baseline metrics through a series of room-parameter perturbation studies. The results demonstrate the advantage of using the signed Wasserstein metric for geometric evaluation tasks and show a promising performance for room parameter optimization within a differentiable Image-Source model.