  This report describes our systems submitted to the DCASE2021 challenge task
3: sound event localization and detection (SELD) with directional interference.
Our previous system based on activity-coupled Cartesian direction of arrival
(ACCDOA) representation enables us to solve a SELD task with a single target.
This ACCDOA-based system with efficient network architecture called RD3Net and
data augmentation techniques outperformed state-of-the-art SELD systems in
terms of localization and location-dependent detection. Using the ACCDOA-based
system as a base, we perform model ensembles by averaging outputs of several
systems trained with different conditions such as input features, training
folds, and model architectures. We also use the event independent network v2
(EINV2)-based system to increase the diversity of the model ensembles. To
generalize the models, we further propose impulse response simulation (IRS),
which generates simulated multi-channel signals by convolving simulated room
impulse responses (RIRs) with source signals extracted from the original
dataset. Our systems significantly improved over the baseline system on the
development dataset.
