  Supervised models for speech enhancement are trained using artificially
generated mixtures of clean speech and noise signals. However, the synthetic
training conditions may not accurately reflect real-world conditions
encountered during testing. This discrepancy can result in poor performance
when the test domain significantly differs from the synthetic training domain.
To tackle this issue, the UDASE task of the 7th CHiME challenge aimed to
leverage real-world noisy speech recordings from the test domain for
unsupervised domain adaptation of speech enhancement models. Specifically, this
test domain corresponds to the CHiME-5 dataset, characterized by real
multi-speaker and conversational speech recordings made in noisy and
reverberant domestic environments, for which ground-truth clean speech signals
are not available. In this paper, we present the objective and subjective
evaluations of the systems that were submitted to the CHiME-7 UDASE task, and
we provide an analysis of the results. This analysis reveals a limited
correlation between subjective ratings and several supervised nonintrusive
performance metrics recently proposed for speech enhancement. Conversely, the
results suggest that more traditional intrusive objective metrics can be used
for in-domain performance evaluation using the reverberant LibriCHiME-5 dataset
developed for the challenge. The subjective evaluation indicates that all
systems successfully reduced the background noise, but always at the expense of
increased distortion. Out of the four speech enhancement methods evaluated
subjectively, only one demonstrated an improvement in overall quality compared
to the unprocessed noisy speech, highlighting the difficulty of the task. The
tools and audio material created for the CHiME-7 UDASE task are shared with the
community.
