A Link Loss Model for the On-Body Propagation Channel for Binaural Hearing Aids

Binaural hearing aids communicate with each other through a wireless link for synchronization. An analytical propagation model is useful to estimate the ear-to-ear link loss for such binaural hearing aids. This paper presents an analytical model for the deterministic component of the ear-to-ear link loss. The model takes into account the dominant paths having most of the power of the creeping wave from the transceiver in one ear to the transceiver in the other ear, and the effect of the protruding part of the outer ear, called pinna. Simulations are done to validate the model using in-the-ear placement of antennas at 2.45 GHz on numerical heterogeneous phantoms of different age-groups and head sizes showing a good agreement with the model. The ear-to-ear link loss for a numerical homogeneous specific anthropomorphic mannequin (SAM) phantom is compared with a numerical heterogeneous phantom. The loss for the SAM phantom is found to be 30 dB lower than that for the heterogeneous phantom. It is shown that the absence of the pinna and the lossless shell in the SAM phantom underestimate the link loss. The effect of the pinnas is verified through measurements on a phantom where we have included the pinnas fabricated by 3-D printing.