“…Meanwhile, deep learning based systems make use of raw inputs such as waveforms or spectrograms, with a trained feature extractor. Spectrograms, in which both temporal and spectral feature elements are well represented, have been explored by a wide range of deep and convolutional neural networks (CNNs) [4], [5], [6], [7] and recurrent neural networks (RNNs) [8]. Comparing between machine learning approaches with hand-crafted features, and deep learning systems with trained feature extractors, the latter are widely reported as being more effective for respiratory classification tasks [4], [6], [7].…”