ASPED: An Audio Dataset for Detecting Pedestrians

We introduce the new audio analysis task of pedestrian detection and present a new large-scale dataset for this task. While the preliminary results prove the viability of using audio approaches for pedestrian detection, they also show that this challenging task cannot be easily solved with standard approaches.Comment: 4+1 page

Polyphonic Sound Event Tracking Using Linear Dynamical Systems

In this paper, a system for polyphonic sound event detection and tracking is proposed, based on spectrogram factorisation techniques and state space models. The system extends probabilistic latent component analysis (PLCA) and is modelled around a 4-dimensional spectral template dictionary of frequency, sound event class, exemplar index, and sound state. In order to jointly track multiple overlapping sound events over time, the integration of linear dynamical systems (LDS) within the PLCA inference is proposed. The system assumes that the PLCA sound event activation is the (noisy) observation in an LDS, with the latent states corresponding to the true event activations. LDS training is achieved using fully observed data, making use of ground truth-informed event activations produced by the PLCA-based model. Several LDS variants are evaluated, using polyphonic datasets of office sounds generated from an acoustic scene simulator, as well as real and synthesized monophonic datasets for comparative purposes. Results show that the integration of LDS tracking within PLCA leads to an improvement of +8.5-10.5% in terms of frame-based F-measure as compared to the use of the PLCA model alone. In addition, the proposed system outperforms several state-of-the-art methods for the task of polyphonic sound event detection

DETECTION OF OVERLAPPING ACOUSTIC EVENTS USING A TEMPORALLY-CONSTRAINED PROBABILISTIC MODEL

In this paper, a system for overlapping acoustic event detection is proposed, which models the temporal evolution of sound events. The system is based on probabilistic latent component analysis, supporting the use of a sound event dictionary where each exemplar consists of a succession of spectral templates. The temporal succession of the templates is controlled through event class-wise Hidden Markov Models (HMMs). As input time/frequency representation, the Equivalent Rectangular Bandwidth (ERB) spectrogram is used. Experiments are carried out on polyphonic datasets of office sounds generated using an acoustic scene simulator, as well as real and synthesized monophonic datasets for comparative purposes. Results show that the proposed system outperforms several state-of-the-art methods for overlapping acoustic event detection on the same task, using both frame-based and event-based metrics, and is robust to varying event density and noise levels

음향 이벤트 탐지를 위한 효율적 데이터 활용 및 약한 교사학습 기법

학위논문(박사)--서울대학교 대학원 :공과대학 전기·컴퓨터공학부,2020. 2. 김남수.Conventional audio event detection (AED) models are based on supervised approaches. For supervised approaches, strongly labeled data is required. However, collecting large-scale strongly labeled data of audio events is challenging due to the diversity of audio event types and labeling difficulties. In this thesis, we propose data-efficient and weakly supervised techniques for AED. In the first approach, a data-efficient AED system is proposed. In the proposed system, data augmentation is performed to deal with the data sparsity problem and generate polyphonic event examples. An exemplar-based noise reduction algorithm is proposed for feature enhancement. For polyphonic event detection, a multi-labeled deep neural network (DNN) classifier is employed. An adaptive thresholding algorithm is applied as a post-processing method for robust event detection in noisy conditions. From the experimental results, the proposed algorithm has shown promising performance for AED on a low-resource dataset. In the second approach, a convolutional neural network (CNN)-based audio tagging system is proposed. The proposed model consists of a local detector and a global classifier. The local detector detects local audio words that contain distinct characteristics of events, and the global classifier summarizes the information to predict audio events on the recording. From the experimental results, we have found that the proposed model outperforms conventional artificial neural network models. In the final approach, we propose a weakly supervised AED model. The proposed model takes advantage of strengthening feature propagation from DenseNet and modeling channel-wise relationships by SENet. Also, the correlations among segments in audio recordings are represented by a recurrent neural network (RNN) and conditional random field (CRF). RNN utilizes contextual information and CRF post-processing helps to refine segment-level predictions. We evaluate our proposed method and compare its performance with a CNN based baseline approach. From a number of experiments, it has been shown that the proposed method is effective both on audio tagging and weakly supervised AED.일반적인 음향 이벤트 탐지 시스템은 교사학습을 통해 훈련된다. 교사학습을 위해서는 강한 레이블 데이터가 요구된다. 하지만 강한 레이블 데이터는 음향 이벤트의 다양성 및 레이블의 난이도로 인해 큰 데이터베이스를 구축하기 어렵다는 문제가 있다. 본 논문에서는 이러한 문제를 해결하기 위해 음향 이벤트 탐지를 위한 데이터 효율적 활용 및 약한 교사학습 기법에 대해 제안한다. 첫 번째 접근법으로서, 데이터 효율적인 음향 이벤트 탐지 시스템을 제안한다. 제안된 시스템에서는 데이터 증대 기법을 사용해 데이터 희소성 문제에 대응하고 중첩 이벤트 데이터를 생성하였다. 특징 벡터 향상을 위해 잡음 억제 기법이 사용되었고 중첩 음향 이벤트 탐지를 위해 다중 레이블 심층 인공신경망(DNN) 분류기가 사용되었다. 실험 결과, 제안된 알고리즘은 불충분한 데이터에서도 우수한 음향 이벤트 탐지 성능을 나타내었다. 두 번째 접근법으로서, 컨볼루션 신경망(CNN) 기반 오디오 태깅 시스템을 제안한다. 제안된 모델은 로컬 검출기와 글로벌 분류기로 구성된다. 로컬 검출기는 고유한 음향 이벤트 특성을 포함하는 로컬 오디오 단어를 감지하고 글로벌 분류기는 탐지된 정보를 요약하여 오디오 이벤트를 예측한다. 실험 결과, 제안된 모델이 기존 인공신경망 기법보다 우수한 성능을 나타내었다. 마지막 접근법으로서, 약한 교사학습 음향 이벤트 탐지 모델을 제안한다. 제안된 모델은 DenseNet의 구조를 활용하여 정보의 원활한 흐름을 가능하게 하고 SENet을 활용해 채널간의 상관관계를 모델링 한다. 또한, 오디오 신호에서 부분 간의 상관관계 정보를 재순환 신경망(RNN) 및 조건부 무작위 필드(CRF)를 사용해 활용하였다. 여러 실험을 통해 제안된 모델이 기존 CNN 기반 기법보다 오디오 태깅 및 음향 이벤트 탐지 모두에서 더 나은 성능을 나타냄을 보였다.1 Introduction 1 2 Audio Event Detection 5 2.1 Data-Ecient Audio Event Detection 6 2.2 Audio Tagging 7 2.3 Weakly Supervised Audio Event Detection 9 2.4 Metrics 10 3 Data-Ecient Techniques for Audio Event Detection 17 3.1 Introduction 17 3.2 DNN-Based AED system 18 3.2.1 Data Augmentation 20 3.2.2 Exemplar-Based Approach for Noise Reduction 21 3.2.3 DNN Classier 22 3.2.4 Post-Processing 23 3.3 Experiments 24 3.4 Summary 27 4 Audio Tagging using Local Detector and Global Classier 29 4.1 Introduction 29 4.2 CNN-Based Audio Tagging Model 31 4.2.1 Local Detector and Global Classier 32 4.2.2 Temporal Localization of Events 34 4.3 Experiments 34 4.3.1 Dataset and Feature 34 4.3.2 Model Training 35 4.3.3 Results 36 4.4 Summary 39 5 Deep Convolutional Neural Network with Structured Prediction for Weakly Supervised Audio Event Detection 41 5.1 Introduction 41 5.2 CNN with Structured Prediction for Weakly Supervised AED 46 5.2.1 DenseNet 47 5.2.2 Squeeze-and-Excitation 48 5.2.3 Global Pooling for Aggregation 49 5.2.4 Structured Prediction for Accurate Event Localization 50 5.3 Experiments 53 5.3.1 Dataset 53 5.3.2 Feature Extraction 54 5.3.3 DSNet and DSNet-RNN Structures 54 5.3.4 Baseline CNN Structure 56 5.3.5 Training and Evaluation 57 5.3.6 Metrics 57 5.3.7 Results and Discussion 58 5.3.8 Comparison with the DCASE 2017 task 4 Results 61 5.4 Summary 62 6 Conclusions 65 Bibliography 67 요 약 77 감사의 글 79Docto

Time-Frequency Feature Fusion for Noise-Robust Audio Event Classification

This paper explores the use of three different two-dimensional time-frequency features for audio event classification with deep neural network back-end classifiers. The evaluations use spectrogram, cochleogram and constant-Q transform based images for classification of 50 classes of audio events in varying levels of acoustic background noise, revealing interesting performance patterns with respect to noise level, feature image type and classifier. Evidence is obtained that two well-performing features, the spectrogram and cochleogram, make use of information that is potentially complementary in the input features. Feature fusion is thus explored for each pair of features, as well as for all tested features. Results indicate that a fusion of spectrogram and cochleogram information is particularly beneficial, yielding an impressive 50-class accuracy of over 96% in 0dB SNR, and exceeding 99% accuracy in 10dB SNR and above. Meanwhile the cochleogram image feature is found to perform well in extreme noise cases of -5dB and -10dB SNR

Robust audio sensing with multi-sound classification

Audio data is a highly rich form of information, often containing patterns with unique acoustic signatures. In pervasive sensing environments, because of the empowered smart devices, we have witnessed an increasing research interest in sound sensing to detect ambient environment, recognise users' daily activities, and infer their health conditions. However, the main challenge is that the real-world environment often contains multiple sound sources, which can significantly compromise the robustness of the above environment, event, and activity detection applications. In this paper, we explore different approaches in multi-sound classification, and propose a stacked classifier based on the recent advance in deep learning. We evaluate our proposed approach in a comprehensive set of experiments on both sound effect and real-world datasets. The results have demonstrated that our approach can robustly identify each sound category among mixed acoustic signals, without the need of any a priori knowledge about the number and signature of sounds in the mixed signals.Postprin

Deep Neural Networks for Sound Event Detection

The objective of this thesis is to develop novel classification and feature learning techniques for the task of sound event detection (SED) in real-world environments. Throughout their lives, humans experience a consistent learning process on how to assign meanings to sounds. Thanks to this, most of the humans can easily recognize the sound of a thunder, dog bark, door bell, bird singing etc. In this work, we aim to develop systems that can automatically detect the sound events commonly present in our daily lives. Such systems can be utilized in e.g. contextaware devices, acoustic surveillance, bio-acoustical and healthcare monitoring, and smart-home cities.In this thesis, we propose to apply the modern machine learning methods called deep learning for SED. The relationship between the commonly used timefrequency representations for SED (such as mel spectrogram and magnitude spectrogram) and the target sound event labels are highly complex. Deep learning methods such as deep neural networks (DNN) utilize a layered structure of units to extract features from the given sound representation input with increased abstraction at each layer. This increases the network’s capacity to efficiently learn the highly complex relationship between the sound representation and the target sound event labels. We found that the proposed DNN approach performs significantly better than the established classifier techniques for SED such as Gaussian mixture models.In a time-frequency representation of an audio recording, a sound event can often be recognized as a distinct pattern that may exhibit shifts in both dimensions. The intra-class variability of the sound events may cause to small shifts in the frequency domain content, and the time domain shift results from the fact that a sound event can occur at any time for a given audio recording. We found that convolutional neural networks (CNN) are useful to learn shift-invariant filters that are essential for robust modeling of sound events. In addition, we show that recurrent neural networks (RNN) are effective in modeling the long-term temporal characteristics of the sound events. Finally, we combine the convolutional and recurrent layers in a single classifier called convolutional recurrent neural networks (CRNN), which emphasizes the benefits of both and provides state-of-the-art results in multiple SED benchmark datasets.Aside from learning the mappings between the time-frequency representations and the sound event labels, we show that deep learning methods can also be utilized to learn a direct mapping between the the target labels and a lower level representation such as the magnitude spectrogram or even the raw audio signals. In this thesis, the feature learning capabilities of the deep learning methods and the empirical knowledge on the human auditory perception are proposed to be integrated through the means of layer weight initialization with filterbank coefficients. This results with an optimal, ad-hoc filterbank that is obtained through gradient based optimization of the original coefficients to improve the SED performance

Continuous Robust Sound Event Classification Using Time-Frequency Features and Deep Learning

The automatic detection and recognition of sound events by computers is a requirement for a number of emerging sensing and human computer interaction technologies. Recent advances in this field have been achieved by machine learning classifiers working in conjunction with time-frequency feature representations. This combination has achieved excellent accuracy for classification of discrete sounds. The ability to recognise sounds under real-world noisy conditions, called robust sound event classification, is an especially challenging task that has attracted recent research attention. Another aspect of real-word conditions is the classification of continuous, occluded or overlapping sounds, rather than classification of short isolated sound recordings. This paper addresses the classification of noise-corrupted, occluded, overlapped, continuous sound recordings. It first proposes a standard evaluation task for such sounds based upon a common existing method for evaluating isolated sound classification. It then benchmarks several high performing isolated sound classifiers to operate with continuous sound data by incorporating an energy-based event detection front end. Results are reported for each tested system using the new task, to provide the first analysis of their performance for continuous sound event detection. In addition it proposes and evaluates a novel Bayesian-inspired front end for the segmentation and detection of continuous sound recordings prior to classification