In Your Ear: A Multimodal Hearables Device for the Assessment of the State of Body and Mind

It is predicted that the global shipment of smart wearables will approach 302.2 million devices in 2023, increasing from 222.9 million devices in 2019 [1] . It was also forecast in 2019 that the number of ear-worn devices—so-called hearables—would rise to 105.3 million in 2023, from 72 million in 2019 [2] . Given the relatively fixed position of the head with respect to the brain and vital organs in most of the daily activities, hearables provide more consistent recordings compared to more mobile parts of the body, such as the wrists. This allows for robust recordings of the both electroencephalogram (EEG) [3] , [4] , [5] , electrocardiogram (ECG) [6] , and photoplethysmogram (PPG) [7] , together with the derived measures including the heart rate (HR) [4] , respiratory rate [8] , blood oxygen saturation (SpO2) [7] , and blood glucose levels [9] .