SALSA: Spatial Cue-Augmented Log-Spectrogram Features for Polyphonic Sound Event Localization and Detection
Thi Ngoc Tho Nguyen, Karn N. Watcharasupat, Ngoc Khanh Nguyen, Douglas L. Jones, Woon‐Seng Gan
Abstract
Sound event localization and detection (SELD) consists of two subtasks, which are sound event detection and direction-of-arrival estimation. While sound event detection mainly relies on time-frequency patterns to distinguish different sound classes, direction-of-arrival estimation uses amplitude and/or phase differences between microphones to estimate source directions. As a result, it is often difficult to jointly optimize these two subtasks. We propose a novel feature called <i>Spatial cue-Augmented Log-SpectrogrAm</i> (SALSA) with exact time-frequency mapping between the signal power and the source directional cues, which is crucial for resolving overlapping sound sources. The SALSA feature consists of multichannel log-spectrograms stacked along with the normalized principal eigenvector of the spatial covariance matrix at each corresponding time-frequency bin. Depending on the microphone array format, the principal eigenvector can be normalized differently to extract amplitude and/or phase differences between the microphones. As a result, SALSA features are applicable for different microphone array formats such as first-order ambisonics (FOA) and multichannel microphone array (MIC). Experimental results on the TAU-NIGENS Spatial Sound Events 2021 dataset with directional interferences showed that SALSA features outperformed other state-of-the-art features. Specifically, the use of SALSA features in the FOA format increased the F1 score and localization recall by <inline-formula><tex-math notation="LaTeX">$6 \,\%$</tex-math></inline-formula> each, compared to the multichannel log-mel spectrograms with intensity vectors. For the MIC format, using SALSA features increased F1 score and localization recall by <inline-formula><tex-math notation="LaTeX">$16 \,\%$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$7 \,\%$</tex-math></inline-formula>, respectively, compared to using multichannel log-mel spectrograms with generalized cross-correlation spectra.