Case study 2: the result of monosyllabic word test. (a) Speech understanding in quiet. (b) Speech understanding in noise. The data from these two clinical cases, showed that the low and mid frequency hearing (up to 1500 Hz) can be preserved by using the round window surgical approach. These patients needed a restoration of their hearing at the higher frequencies. The cochlear implantation presented a major challenge to the surgeon, as it was necessary to preserve the pre-operative low and middle frequencies hearing levels.