Acoustic environment classification using discrete hartley transform features

Most attention-based methods only concentrate along the time axis, which is insufficient for Acoustic Event Detection (AED).Meanwhile, previous methods for AED rarely considered that target events possess distinct temporal and frequential scales.In this work, we propose a Multi-Scale Time-Frequency Attention (MTFA) module for AED.MTFA gathers information at multiple resolutions to generate a time-frequency attention mask which tells the model where to focus along both time and frequency axis.With MTFA, the model could capture the characteristics of target events with different scales.We demonstrate the proposed method on Task 2 of Detection and Classification of Acoustic Scenes and Events (DCASE) 2017 Challenge.Our method achieves competitive results on both development dataset and evaluation dataset.

In this paper, we present a gated convolutional neural network and a temporal attention-based localization method for audio classification, which won the 1st place in the large-scale weakly supervised sound event detection task of Detection and Classification of Acoustic Scenes and Events (DCASE) 2017 challenge. The audio clips in this task, which are extracted from YouTube videos, are manually labelled with one or more audio tags, but without time stamps of the audio events, hence referred to as weakly labelled data. Two subtasks are defined in this challenge including audio tagging and sound event detection using this weakly labelled data. We propose a convolutional recurrent neural network (CRNN) with learnable gated linear units (GLUs) non-linearity applied on the log Mel spectrogram. In addition, we propose a temporal attention method along the frames to predict the locations of each audio event in a chunk from the weakly labelled data. The performances of our systems were ranked the 1st and the 2nd as a team in these two sub-tasks of DCASE 2017 challenge with F value 55.6% and Equal error 0.73, respectively.

Late fusion framework for Acoustic Scene Classification using LPCC, SCMC, and log-Mel band energies with Deep Neural Networks

Polyphonic sound event detection (SED) is an emerging area with many applications for smart disaster safety, security, life logging, etc. This paper proposes a two-stage polyphonic SED model when strongly labeled data are limited but weakly labeled and unlabeled data are available. The first stage of the proposed SED model is constructed by a residual convolutional recurrent neural network (RCRNN)-based mean teacher model with convolutional block attention module (CBAM)-based attention. Then, the second stage fine-tunes the student model from the first stage by applying the proposed semi-supervised loss function to accommodate the noisy targets of weakly labeled and unlabeled data. The proposed SED model is applied to both Detection and Classification of Acoustic Scenes and Events (DCASE) 2019 Challenge Task 4 and DCASE 2020 Challenge Task 4, and its performance is compared with those of the baseline and top-ranked models from both challenges by measuring the F1-score and polyphonic sound detection score (PSDS). The experiments show that the RCRNN-based first-stage model with CBAM-based attention achieves a higher F1-score and PSDS than the baseline and top-ranked models for both challenges. Furthermore, the proposed two-stage SED model with the semi-supervised loss function improves the F1-score by 6.1% and 4.6% compared to the top-ranked models from DCASE 2019 and 2020, respectively.

This study proposes a sound event localization and detection (SELD) method using imbalanced real and synthetic data via a multi-generator. The proposed method is based on a residual convolutional neural network (RCNN) and a transformer encoder for real spatial sound scenes. SELD aims to classify the sound event, detect the onset and offset of the classified event, and estimate the direction of the sound event. In Detection and Classification of Acoustic Scenes and Events (DCASE) 2022 Task 3, SELD is performed with a few real spatial sound scene data and a relatively large number of synthetic data. When a model is trained using imbalanced data, it can proceed by focusing only on a larger number of data. Thus, a multi-generator that samples real and synthetic data at a specific rate in one batch is proposed to prevent this problem. We applied the data augmentation technique SpecAugment and used time-frequency masking to the dataset. Furthermore, we propose a neural network architecture to apply the RCNN and transformer encoder. Several models were trained with various structures and hyperparameters, and several ensemble models were obtained by “cherry-picking” specific models. Based on the experiment, the single model of the proposed method and the model applied with the ensemble exhibited improved performance compared with the baseline model.

Detection and recognition of loud sounds and characteristic noises can significantly increase the level of safety and ensure timely response to various emergency situations. Audio event detection is the first step in recognizing audio signals in a continuous audio input stream. This article presents a number of problems that are associated with the development of sound event detection systems, such as the deviation for each environment and each sound category, overlapping audio events, unreliable training data, etc. Both methods for detecting monophonic impulsive audio event and polyphonic sound event detection methods which are used in the state-of-the-art sound event detection systems are presented. Such systems are presented in Detection and Classification of Acoustic Scenes and Events (DCASE) challenges and workshops, which take place every year. Beside a majority of works focusing on the improving overall performance in terms of accuracy many other aspects have also been studied. Several systems presented at DCASE 2021 task 4 were considered, and based on their analysis, there was a conclusion about possible future for sound event detection systems. Also the actual directions in the development of modern audio analytics systems are presented, including the study and use of various architectures of neural networks, the use of several data augmentation techniques, such as universal sound separation, etc.

This paper proposes a sound event detection (SED) model using an EfficientNet-B2 and an attention and aggregation-based feature pyramid network (A2-FPN). In particular, the EfficientNet-B2 is first obtained from the pretrained model on the basis of the pretraining, sampling, labeling, and aggregation (PSLA) framework. Then, the A2-FPN module is applied to the outputs of the layers of the EfficientNet-B2 to deal with the different time and frequency resolutions from acoustic features. The aggregated feature map from the A2-FPN module is used as input features to two bidirectional gated recurrent unit layers. Specifically, the proposed A2-FPN-based SED model is trained by the mean-teacher approach to utilize weakly labeled and unlabeled data. Finally, the proposed A2-FPN-based SED model is applied to the detection and classification of acoustic scenes and events (DCASE) 2021 Challenge Task 4. Consequently, it is shown that the polyphonic sound event detection score (PSDS) 1 and 2 of the proposed A2-FPN-based SED model are the higher of 0.03 and 0.172, respectively, than those of the DCASE 2021 Challenge Task 4 baseline.

Common acoustic properties that different classes share degrades the performance of acoustic scene classification systems. This results in a phenomenon where a few confusing pairs of acoustic scenes dominate a significant proportion of all misclassified audio segments. In this article, we propose adopting a knowledge distillation framework that trains deep neural networks using soft labels. Soft labels, extracted from another pre-trained deep neural network, are used to reflect the similarity between different classes that share similar acoustic properties. We also propose utilizing specialist models to provide additional soft labels. Each specialist model in this study refers to a deep neural network that concentrates on discriminating a single pair of acoustic scenes that are frequently misclassified. Self multi-head attention is explored for training specialist deep neural networks to further concentrate on target pairs of classes. The goal of this article is to train a single deep neural network that demonstrates performance equivalent to, or higher than, an ensemble of multiple models, by distilling the knowledge from several models. Diverse experiments conducted using the detection and classification of acoustic scenes and events 2019 task 1-a dataset demonstrate that the knowledge distillation framework is effective in acoustic scene classification. Specialist models successfully decrease the number of misclassified audio segments in the target classes. The final single model with the proposed method that is trained by the proposed knowledge distillation from several models, including specialists trained using an attention mechanism, shows a classification accuracy of 77.63 %, higher than an ensemble of the baseline and multiple specialists.

Acoustic scene classification contains frequently misclassified pairs of classes that share many common acoustic properties. Specific details can provide vital clues for distinguishing such pairs of classes. However, these details are generally not noticeable and are hard to generalize for different data distributions. In this study, we investigate various methods for capturing discriminative information and simultaneously improve the generalization ability. We adopt a max feature map method that replaces conventional non-linear activation functions in deep neural networks; therefore, we apply an element-wise comparison between the different filters of a convolution layer’s output. Two data augmentation methods and two deep architecture modules are further explored to reduce overfitting and sustain the system’s discriminative power. Various experiments are conducted using the “detection and classification of acoustic scenes and events 2020 task1-a” dataset to validate the proposed methods. Our results show that the proposed system consistently outperforms the baseline, where the proposed system demonstrates an accuracy of 70.4% compared to the baseline at 65.1%.

Identifying various acoustic sources can be challenging in both air and underwater settings. This is largely due to the difficulties in data collection, especially in ocean environments, and the variety of background noise they pose. Transformer architecture with self-attention mechanism has proven effective across various machine learning tasks, such as Natural Language Processing (NLP) and image recognition, even in challenging environments. This thesis presents the applications of Transformer in both air and underwater domains. In the air, we developed a Hierarchical Knowledge Distillation (H-KD) framework that utilized the Audio Spectrogram Transformer (AST) [1] architecture as a teacher model. The framework was designed using a multi-stage learning approach and cross-model integration to enhance performance of a low complexity Convolutional Neural Networks (CNN) student model. We applied it to an air acoustic dataset - TAU Urban Acoustic Scenes 2023 Mobile development [2] and demonstrated that it achieved a significantly improved performance compared to the Baseline system [3]. After verifying the model on publicly available datasets, our proposed model was submitted to the 2023 IEEE AASP Challenge on Detection and Classification of Acoustic Scenes and Events (DCASE2023) [3]. In the underwater acoustic signals experiment, we modified and adapted the Hierarchical Token Semantic - Audio Transformer (HTS-AT) [4] architecture to make it better suited underwater environments. We applied it to an underwater acoustic dataset - shipsEar [5] and demonstrated that our proposed method outperformed some of the latest classification methods. The promising results obtained motivate further exploration of Transformer-based approaches in future research to advance the state-of-the-art (SOTA) in Acoustic Signal Classifications (ASC).

This contribution focuses on acoustic event detection and classification for monitoring of elderly people in ambient assistive living environments such as smart homes or nursing homes. We describe an autonomous system for robust detection of acoustic events in various practically relevant acoustic situations that benefits from a voice activity detection inspired preprocessing mechanism. Therefore, various already established voice activity detection schemes have been evaluated beforehand. As a specific use case, we address coughing as an acoustic event of interest which can be interpreted as an indicator for a potentially upcoming illness. After the detection of such events using a psychoacoustically motivated spectro-temporal representation (the so-called cochleogram), we forward its output to a statistical event modeling stage for automatic instantaneous emergency classification and long-term monitoring. The parameters derived by this procedure can then be used to inform medical or care-service personal.

In this paper, we present the results of the Acoustic Event Detection (AED) and Classification (AEC) evaluations carried out in February 2006 by the three participant partners from the CHIL project. The primary evaluation task was AED of the testing portions of the isolated sound databases and seminar recordings produced in CHIL. Additionally, a secondary AEC evaluation task was designed using only the isolated sound databases. The set of meeting-room acoustic event classes and the metrics were agreed by the three partners and ELDA was in charge of the scoring task. In this paper, the various systems for the tasks of AED and AEC and their results are presented.

Multitask learning for acoustic scene classification with topic-based soft labels and a mutual attention mechanism

In this work, we compare the performance of three selected techniques in open set acoustic scenes classification (ASC). We test thresholding of the softmax output of a deep network classifier, which is the most popular technique nowadays employed in ASC. Further we compare the results with the Openmax classifier which is derived from the computer vision field. As the third model, we use the Adapted Class-Conditioned Autoencoder (Adapted C2AE) which is our variation of another computer vision related technique called C2AE. Adapted C2AE encompasses a more fair comparison of the given experiments and simplifies the original inference procedure, making it more applicable in the real-life scenarios. We also analyse two training scenarios: without additional knowledge of unknown classes and another where a limited subset of examples from the unknown classes is available. We find that the C2AE based method outperforms the thresholding and Openmax, obtaining $85.5\%$ Area Under the Receiver Operating Characteristic curve (AUROC) and $66\%$ of open set accuracy on data used in Detection and Classification of Acoustic Scenes and Events Challenge 2019 Task 1C.

Each edition of the challenge on Detection and Classification of Acoustic Scenes and Events DCASE contained several tasks involving sound event detection in different setups. DCASE 2017 presented participants with three such tasks, each having specific datasets and detection requirements: Task 2, in which target sound events were very rare in both training and testing data, Task 3 having overlapping events annotated in real-life audio, and Task 4, in which only weakly labeled data were available for training. In this paper, we present three tasks, including the datasets and baseline systems, and analyze the challenge entries for each task. We observe the popularity of methods using deep neural networks, and the still widely used mel frequency-based representations, with only few approaches standing out as radically different. Analysis of the systems behavior reveals that task-specific optimization has a big role in producing good performance; however, often this optimization closely follows the ranking metric, and its maximization/minimization does not result in universally good performance. We also introduce the calculation of confidence intervals based on a jackknife resampling procedure to perform statistical analysis of the challenge results. The analysis indicates that while the 95% confidence intervals for many systems overlap, there are significant differences in performance between the top systems and the baseline for all tasks.