Dilated U-net based approach for multichannel speech enhancement from First-Order Ambisonics recordings
This is an incremental improvement for speech recognition systems in noisy environments.
The paper tackles speech enhancement in multichannel Ambisonics recordings under adverse conditions like reverberation and competitive speakers, showing that a dilated U-net architecture improves word error rates and reduces parameters by half compared to previous methods.
We present a CNN architecture for speech enhancement from multichannel first-order Ambisonics mixtures. The data-dependent spatial filters, deduced from a mask-based approach, are used to help an automatic speech recognition engine to face adverse conditions of reverberation and competitive speakers. The mask predictions are provided by a neural network, fed with rough estimations of speech and noise amplitude spectra, under the assumption of known directions of arrival. This study evaluates the replacing of the recurrent LSTM network previously investigated by a convolutive U-net under more stressing conditions with an additional second competitive speaker. We show that, due to more accurate short-term masks prediction, the U-net architecture brings some improvements in terms of word error rate. Moreover, results indicate that the use of dilated convolutive layers is beneficial in difficult situations with two interfering speakers, and/or where the target and interferences are close to each other in terms of the angular distance. Moreover, these results come with a two-fold reduction in the number of parameters.