Human pulse wave detection with consumer earphones and headphones

Dynamic earphones/headphones and microphones can detect sounds below the human audible frequency. Based on this principle, we propose a new method of human pulse measurement using consumer earphones and headphones. It is a simple signal separation-based method utilizing pressure changes inside the ear canal and around the tragus caused by heartbeats. As a result of feasibility evaluation using an electrocardiogram, the pulses derived by the earphone/headphone were highly feasible in terms of accurate peak-to-peak determination. Furthermore, we estimated the frequency characteristics of the audio devices at the frequency of interest, the center frequency of the heart rate (around 1.4 Hz), which enables us to reproduce the original, non-distorted pulse waveform. Although this is an entirely different methodology from photoplethysmography, it is promising because heart rate can be measured while listening to music.