Acoustic scene recordings are represented by different types of handcrafted or Neural Network-derived features. These features, typically of thousands of dimensions, are classified in state of the art approaches using kernel machines, such as the Support Vector Machines (SVM). However, the complexity of training these methods increases with the dimensionality of these input features and the size of the dataset. A solution is to map the input features to a randomized lower-dimensional feature space. The resulting random features can approximate non-linear kernels with faster linear kernel computation. In this work, we computed a set of 6,553 input features and used them to compute random features to approximate three types of kernels, Gaussian, Laplacian and Cauchy. We compared their performance using an SVM in the context of the DCASE Task 1 - Acoustic Scene Classification. Experiments show that both, input and random features outperformed the DCASE baseline by an absolute 4 . Moreover, the random features reduced the dimensionality of the input by more than three times with minimal loss of performance and by more than six times and still outperformed the baseline. Hence, random features could be employed by state of the art approaches to compute low-storage features and perform faster kernel computations.
The DCASE Task 1 - Acoustic Scene Classification (ASC) aims to identify a recording as belonging to a predefined set of scene-classes that characterizes an environment, for example , , or . Typically, ASC approaches capture the diverse characteristics from the audio signal by computing different types of features, either hand-crafted @cite_8 @cite_2 @cite_11 @cite_13 @cite_14 or derived from Neural Networks @cite_1 @cite_12 @cite_6 . These features are commonly of high-dimensionality (up to ten of thousands) and state of the art ASC approaches classified them using Support Vector Machines, the best known member of kernel methods.
@cite_14 @cite_8 @cite_1 @cite_6 @cite_2 @cite_13 @cite_12 @cite_11
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In this paper we present our work on Task 1 Acoustic Scene Classification and Task 3 Sound Event Detection in Real Life Recordings. Among our experiments we have low-level and high-level features, classifier optimization and other heuristics specific to each task. Our performance for both tasks improved the baseline from DCASE: for Task 1 we achieved an overall accuracy of 78.9 compared to the baseline of 72.6 and for Task 3 we achieved a Segment-Based Error Rate of 0.48 compared to the baseline of 0.91. Acoustic Event Classification (AEC) has become a significant task for machines to perceive the surrounding auditory scene. However, extracting effective representations that capture the underlying characteristics of the acoustic events is still challenging. Previous methods mainly focused on designing the audio features in a 'hand-crafted' manner. Interestingly, data-learnt features have been recently reported to show better performance. Up to now, these were only considered on the frame-level. In this paper, we propose an unsupervised learning framework to learn a vector representation of an audio sequence for AEC. This framework consists of a Recurrent Neural Network (RNN) encoder and a RNN decoder, which respectively transforms the variable-length audio sequence into a fixed-length vector and reconstructs the input sequence on the generated vector. After training the encoder-decoder, we feed the audio sequences to the encoder and then take the learnt vectors as the audio sequence representations. Compared with previous methods, the proposed method can not only deal with the problem of arbitrary-lengths of audio streams, but also learn the salient information of the sequence. Extensive evaluation on a large-size acoustic event database is performed, and the empirical results demonstrate that the learnt audio sequence representation yields a significant performance improvement by a large margin compared with other state-of-the-art hand-crafted sequence features for AEC. We learn rich natural sound representations by capitalizing on large amounts of unlabeled sound data collected in the wild. We leverage the natural synchronization between vision and sound to learn an acoustic representation using two-million unlabeled videos. Unlabeled video has the advantage that it can be economically acquired at massive scales, yet contains useful signals about natural sound. We propose a student-teacher training procedure which transfers discriminative visual knowledge from well established visual recognition models into the sound modality using unlabeled video as a bridge. Our sound representation yields significant performance improvements over the state-of-the-art results on standard benchmarks for acoustic scene object classification. Visualizations suggest some high-level semantics automatically emerge in the sound network, even though it is trained without ground truth labels. In this paper, we present recent experiments on using Artificial Neural Networks (ANNs), a new “delayed” approach to speech vs. non-speech segmentation, and extraction of large-scale pooling feature (LSPF) for detecting “events” within consumer videos, using the audio channel only. A “event” is defined to be a sequence of observations in a video, that can be directly observed or inferred. Ground truth is given by a semantic description of the event, and by a number of example videos. We describe and compare several algorithmic approaches, and report results on the 2013 TRECVID Multimedia Event Detection (MED) task, using arguably the largest such research set currently available. The presented system achieved the best results in most audio-only conditions. While the overall finding is that MFCC features perform best, we find that ANN as well as LSP features provide complementary information at various levels of temporal resolution. This paper provides analysis of both low-level and high-level features, investigating their relative contributions to overall system performance. We consider the question: what can be learnt by looking at and listening to a large number of unlabelled videos? There is a valuable, but so far untapped, source of information contained in the video itself -- the correspondence between the visual and the audio streams, and we introduce a novel "Audio-Visual Correspondence" learning task that makes use of this. Training visual and audio networks from scratch, without any additional supervision other than the raw unconstrained videos themselves, is shown to successfully solve this task, and, more interestingly, result in good visual and audio representations. These features set the new state-of-the-art on two sound classification benchmarks, and perform on par with the state-of-the-art self-supervised approaches on ImageNet classification. We also demonstrate that the network is able to localize objects in both modalities, as well as perform fine-grained recognition tasks.