Multimodal Cognitive Load Estimation with Radio Frequency Sensing and Pupillometry in Complex Auditory Environments

The detection of listening effort or cognitive load (CL) has been a major research challenge in recent years. Most conventional techniques utilise physiological or audio-visual sensors and are privacy-invasive and computationally complex. The challenges of synchronization, data alignment and accessibility limitations potentially increase the noise and error probability, compromising the accuracy of CL estimates. This innovative work presents a multi-modal, non-invasive and privacy-preserving approach that combines Radio Frequency (RF) and pupillometry sensing to address these challenges. Custom RF sensors are first designed and developed to capture blood flow changes in specific brain regions with high spatial resolution. Next, multi-modal fusion with pupillometry sensing is proposed and shown to offer a robust assessment of cognitive and listening effort through pupil size and pupil dilation. Our novel approach evaluates RF sensing to estimate CL from cerebral blood flow variations utilizing pupillometry as a baseline. A first-of-its-kind, multi-modal dataset is collected as a new benchmark resource in a controlled environment with participants to comprehend target speech with varying background noise levels. The framework is statistically evaluated using intraclass correlation for pupillometry data (average ICC> 0.95). The correlation between pupillometry and RF data is established through Pearson's correlation (average PCC> 0.79). Further, CL is classified into high and low categories based on RF data using K-means clustering. Future work involves integrating RF sensors with glasses to estimate listening effort for hearing-aid users and utilising RF measurements to optimize speech enhancement based on individual's listening effort and complexity of acoustic environment.