  Room impulse response (RIR) functions capture how the surrounding physical
environment transforms the sounds heard by a listener, with implications for
various applications in AR, VR, and robotics. Whereas traditional methods to
estimate RIRs assume dense geometry and/or sound measurements throughout the
environment, we explore how to infer RIRs based on a sparse set of images and
echoes observed in the space. Towards that goal, we introduce a
transformer-based method that uses self-attention to build a rich acoustic
context, then predicts RIRs of arbitrary query source-receiver locations
through cross-attention. Additionally, we design a novel training objective
that improves the match in the acoustic signature between the RIR predictions
and the targets. In experiments using a state-of-the-art audio-visual simulator
for 3D environments, we demonstrate that our method successfully generates
arbitrary RIRs, outperforming state-of-the-art methods and -- in a major
departure from traditional methods -- generalizing to novel environments in a
few-shot manner. Project: http://vision.cs.utexas.edu/projects/fs_rir.
