The measurement of transmission loss and absorption coefficient of the rat and porcine skin: Synthesizing artificial material for an implantable microphone test

With the advent of totally implantable hearing aids, the implementation and measurement of the microphone becomes an important issue. Engineers have to consider effects of the skin on the implantable microphone that did not exist in conventional hearing aid tests. In this paper, the transmission loss (TL) and absorption coefficient of rat and porcine skins were measured, and the synthesized skin was then implemented by using a gelatin gel that is widely used as an ultrasound phantom. From the measurement, the TL for rat and porcine skin was found to be 23.5 ± 2.7 dB and 30.4 ± 2.8 dB (mean ± std) at 1 kHz, respectively. Further, the absorption coefficients or the rat and porcine skin were measured as 0.029 ± 0.011 and 0.031 ± 0.012 at 1 kHz, respectively. From the measurements, the TL values were found to be significantly increased at the high frequency and the absorption coefficients did not changed significantly in the 1–6 kHz range. In additionally, the synthesized tissues also showed similar properties when compared with the animal experiments and they could be used to replace animal experiments for implantable microphones.