Bag-of-Deep-Features: Noise-Robust Deep Feature Representations for Audio Analysis

In the era of deep learning, research into the classification of various components of the acoustic environment, especially in-the-wild recordings, is gaining in popularity. This is due in part to the increasing computational capacities and the expanding amount of real-world data available on social multimedia. However, the noisy nature of this data can add an additional complexity to the already complex deep learning systems. Herein, we tackle this issue by quantising deep feature representations of various in-the-wild audio data sets. The aim of this paper is twofold: 1) to assess the feasibility of the proposed feature quantisation task, and 2) to compare the efficacy of various feature spaces extracted from different fully connected deep neural networks to classify six real-world audio corpora. For the classification, we extract two feature sets: i) DEEP SPECTRUM features which are derived from forwarding the visual representations of the audio instances, in particular mel-spectrograms through very deep task-independent pre-trained Convolutional Neural Networks (CNNs), and ii) Bag-of-Deep-Features (BODF) which is the quantisation of the DEEP SPECTRUM features. Using BODF, we show the suitability of quantising the deep representations for noisy in-the-wild audio data. Finally, we analyse the effect of early and late fusion of the CNN features and models on the classification results.