SensorHub: Multimodal Sensing in Real-Life Enables Home-Based Studies. Chromik, Jonas; Kirsten, Kristina; Herdick, Arne; Kappattanavar, Arpita Mallikarjuna; Arnrich, Bert in Sensors (2022). 22(1)
Observational studies are an important tool for determining whether the findings from controlled experiments can be transferred into scenarios that are closer to subjects’ real-life circumstances. A rigorous approach to observational studies involves collecting data from different sensors to comprehensively capture the situation of the subject. However, this leads to technical difficulties especially if the sensors are from different manufacturers, as multiple data collection tools have to run simultaneously. We present SensorHub, a system that can collect data from various wearable devices from different manufacturers, such as inertial measurement units, portable electrocardiographs, portable electroencephalographs, portable photoplethysmographs, and sensors for electrodermal activity. Additionally, our tool offers the possibility to include ecological momentary assessments (EMAs) in studies. Hence, SensorHub enables multimodal sensor data collection under real-world conditions and allows direct user feedback to be collected through questionnaires, enabling studies at home. In a first study with 11 participants, we successfully used SensorHub to record multiple signals with different devices and collected additional information with the help of EMAs. In addition, we evaluated SensorHub’s technical capabilities in several trials with up to 21 participants recording simultaneously using multiple sensors with sampling frequencies as high as 1000 Hz. We could show that although there is a theoretical limitation to the transmissible data rate, in practice this limitation is not an issue and data loss is rare. We conclude that with modern communication protocols and with the increasingly powerful smartphones and wearables, a system like our SensorHub establishes an interoperability framework to adequately combine consumer-grade sensing hardware which enables observational studies in real life.
Have Your Cake and Log it Too: A Pilot Study Leveraging IMU Sensors for Real-time Food Journaling Notifications Kappattanavar, Arpita; Kremser, Marten; Arnrich, Bert (2022). (Vol. 5) 532–541.
Wearable electroencephalography and multi-modal mental state classification: A systematic literature review. Anders, Christoph; Arnrich, Bert in Computers in Biology and Medicine (2022). 150 106088.
Background: Wearable multi-modal time-series classification applications outperform their best uni-modal counterparts and hold great promise. A modality that directly measures electrical correlates from the brain is electroencephalography. Due to varying noise sources, different key brain regions, key frequency bands, and signal characteristics like non-stationarity, techniques for data pre-processing and classification algorithms are task-dependent. Method: Here, a systematic literature review on mental state classification for wearable electroencephalography is presented. Four search terms in different combinations were used for an in-title search. The search was executed on the 29th of June 2022, across Google Scholar, PubMed, IEEEXplore, and ScienceDirect. 76 most relevant publications were set into context as the current state-of-the-art in mental state time-series classification. Results: Pre-processing techniques, features, and time-series classification models were analyzed. Across publications, a window length of one second was mainly chosen for classification and spectral features were utilized the most. The achieved performance per time-series classification model is analyzed, finding linear discriminant analysis, decision trees, and k-nearest neighbors models outperform support-vector machines by a factor of up to 1.5. A historical analysis depicts future trends while under-reported aspects relevant to practical applications are discussed. Conclusions: Five main conclusions are given, covering utilization of available area for electrode placement on the head, most often or scarcely utilized features and time-series classification model architectures, baseline reporting practices, as well as explainability and interpretability of Deep Learning. The importance of a ‘test battery’ assessing the influence of data pre-processing and multi-modality on time-series classification performance is emphasized.
Quantifying Cognitive Load from Voice using Transformer-Based Models and a Cross-Dataset Evaluation. Hecker, Pascal; Kappattanavar, Arpita M; Schmitt, Maximilian; Moontaha, Sidratul; Wagner, Johannes; Eyben, Florian; Schuller, Björn W; Arnrich, Bert (2022). 337–344.
Towards Multi-Modal Recordings in Daily Life: A Baseline Assessment of an Experimental Frame- work. Moontaha, Sidratul; Anders, Christoph; Arnrich, Bert (2022). 27–30.
Quantifying Cognitive Load from Voice using Transformer-Based Models and a Cross-Dataset Evaluation. Hecker, Pascal; Kappattanavar, Arpita M.; Schmitt, Maximilian; Moontaha, Sidratul; Wagner, Johannes; Eyben, Florian; Schuller, Björn W.; Arnrich, Bert (2022). 337–344.
Cognitive load is frequently induced in laboratory setups to measure responses to stress, and its impact on voice has been studied in the field of computational paralinguistics. One dataset on this topic was provided in the Computational Paralinguistics Challenge (ComParE) 2014, and therefore offers great comparability. Recently, transformer-based deep learning architectures established a new state-of-the-art and are finding their way gradually into the audio domain. In this context, we investigate the performance of popular transformer architectures in the audio domain on the ComParE 2014 dataset, and the impact of different pre-training and fine-tuning setups on these models. Further, we recorded a small custom dataset, designed to be comparable with the ComParE 2014 one, to assess cross-corpus model generalisability. We find that the transformer models outperform the challenge baseline, the challenge winner, and more recent deep learning approaches. Models based on the ‘large’ architecture perform well on the task at hand, while models based on the ‘base’ architecture perform at chance level. Fine-tuning on related domains (such as ASR or emotion), before fine-tuning on the targets, yields no higher performance compared to models pre-trained only in a self-supervised manner. The generalisability of the models between datasets is more intricate than expected, as seen in an unexpected low performance on the small custom dataset, and we discuss potential ‘hidden’ underlying discrepancies between the datasets. In summary, transformer-based architectures outperform previous attempts to quantify cognitive load from voice. This is promising, in particular for healthcare-related problems in computational paralinguistics applications, since datasets are sparse in that realm.
Towards Multi-Modal Recordings in Daily Life: A Baseline Assessment of an Experimental Framework Anders, Christoph; Moontaha, Sidratul; Arnrich, Bert in IS (2022). (Vol. H) 27–30. Information Society.
Background: Wearable devices can record physiological signals from humans to enable an objective assessment of their Mental State. In the future, such devices will enable researchers to work on paradigms outside, rather than only inside, of controlled laboratory environments. This transition requires a paradigm shift on how experiments are conducted, and introduces new challenges. Method: Here, an experimental framework for multi-modal baseline assessments is presented. The developed test battery covers stimuli and questionnaire presenters, and multi-modal data can be recorded in parallel, such as Photoplethysmography, Electroencephalography, Acceleration, and Electrodermal Activity data. The multi-modal data is extracted using a single platform, and synchronized using a shake detection tool. A baseline was recorded from eight participants in a controlled environment. Using Leave-One-Out Cross-Validation, the resampling of data, the ideal window size, and the applicability of Deep Learning for Mental Workload Classification were evaluated. In addition, participants were polled on the acceptance of using the wearable devices. Results: The binary classification performance declined by an average of 7.81% when using eye-blink removal, underlining the importance of data synchronization, correct artefact identification, evaluating and developing artefact removal techniques, and investigating on the robustness of the multi-modal setup. Experiments showed that the optimal window size for the acquired data is 30 seconds for Mental Workload classification, with which a Random Forest classifier and an optimized Deep Convolutional Neural Network achieved the best-balanced classification accuracy of 70.27% and 74.16%, respectively. Conclusions: This baseline assessment gives valuable insights on how to prototype stimulus presentation with different wearable devices and suggests future work packages, paving the way for researchers to investigate new paradigm outside of controlled environments.
