  Source separation (SS) aims to separate individual sources from an audio
recording. Sound event detection (SED) aims to detect sound events from an
audio recording. We propose a joint separation-classification (JSC) model
trained only on weakly labelled audio data, that is, only the tags of an audio
recording are known but the time of the events are unknown. First, we propose a
separation mapping from the time-frequency (T-F) representation of an audio to
the T-F segmentation masks of the audio events. Second, a classification
mapping is built from each T-F segmentation mask to the presence probability of
each audio event. In the source separation stage, sources of audio events and
time of sound events can be obtained from the T-F segmentation masks. The
proposed method achieves an equal error rate (EER) of 0.14 in SED,
outperforming deep neural network baseline of 0.29. Source separation SDR of
8.08 dB is obtained by using global weighted rank pooling (GWRP) as probability
mapping, outperforming the global max pooling (GMP) based probability mapping
giving SDR at 0.03 dB. Source code of our work is published.
