Investigation of wireless data transmission between hearing aids

Electrodes were developed for use in a wireless data-sharing system between hearing aids. Electrodes were placed on the outsides of custom-fit, in-the-ear (ITE) and one-size-fits-all behind-the-ear (BTE) hearing aid shells. Impedance measurements and gains were collected for six electrode-pair configurations at 21.5, 64.8, 128.3, and 216.4 MHz for multiple subjects. Electrodes were coated with a standard hearing aid lacquer or with Galxyl-parylene. Preliminary comparisons of impedance values of similar electrodes inserted in subjects' ears showed that for each design, impedance values were fairly constant for all subjects, so mismatch loss variation is not significant across the range of impedances obtained for different subjects. Thus a standard impedance can be chosen for ease of manufacturing hearing aids using this technology. Transducer losses across subjects' heads were generally between 60 and 80 dB at all tested frequencies, but were lower at higher frequencies.