# Round Window Reinforcement-Induced Changes in Intracochlear Sound Pressure
## 3 Results
### Validation of the Experimental Method
#### 3.1.3 Effect of RWM Reinforcement on ICSP Measurement  
The typical change in ICSP gain due to RWM reinforcement that was observed in the present study is illustrated in the data from four simultaneous ICSP measurements on HTB-10 and HTB-11 using cartilage and soft tissue as reinforcement material (cf. Figure 5). The individual figures show the ICSP gain for both scalae before (baseline) and after the RWM reinforcement. In general, a considerable increase in ICSP after RWM reinforcement was identified in ST at frequencies below 1 kHz. In SV, the corresponding pressure increase is moderate or even negligible. The sample HTB-10 experienced the largest increase in ST pressure by more than 15 dB after adding soft tissue to the RWM (cf. Figure 5A). The cartilage showed similar behavior to the soft tissue, despite its higher material stiffness (cf. Figure 5B). It was expected that soft tissue could be better adapted to the surface geometry of the RWM and hence allow for a more repeatable and efficient means of RWM reinforcement than using stiffer cartilage material. However, using HTB-11 cartilage led to a higher pressure in ST than using soft tissue (13 dB versus 5 dB, cf. Figure 5C,D), but overall, the change in ST pressure was less pronounced compared to that for HTB-10, especially if the effect of reinforcement on the SV pressure was considered. The investigations on HTB-10 nicely demonstrate that the pressure difference across the partition can be considerably reduced or can even vanish after RWM reinforcement and at frequencies below 500 Hz. Consequently, a reduced hearing sensation within that frequency range might result from RWM manipulation. To highlight the effect of RWM reinforcement on the ICSP in ST and SV for all considered HTBs, the ratio between the ICSP after (indicated with an apostrophe) and before (indicated as the baseline) reinforcement was calculated and denoted as the relative pressure gain. The corresponding data are shown in Figure 6. Figure 6A,B quantify the effect of cartilage reinforcement in ST and SV for all considered HTBs together with the respective medians, and Figure 6C,D show the same but for silicone used as a reinforcement material. Figure 5: Two exemplary cases for the ICSP gain changes in ST and SV after the reinforcement of the RWM with soft tissue and cartilage compared to the respective baselines for HTB-10 (**A**,**B**) and HTB-11 (**C**,**D**). The bold lines represent the ICSP gain after reinforcement in each scenario for ST and SV (red and blue, respectively) and the dotted line pattern for the baselines in the same light color shades. Finally, the median curves for all the reinforcement materials are summarized in Figure 6E,F. The individual data for soft tissue are not shown, since they do not provide more insight into the effect of RWM reinforcement on the inner ear sound pressure. The data confirm the aforementioned considerably higher increase in sound pressure in ST compared to SV after RWM reinforcement and within the low-frequency range (<2 kHz), where pressure changes are attributed to RWM reinforcement. The large variation in relative pressure gain between the individual samples is noticeable. With cartilage reinforcement, the gain in ST can reach a maximum gain of up to 25 dB (HTB-12), but in another trial a maximum gain as small as 5 dB was identified (HTB-9). The other reinforcement materials show similar variations between the samples. Considering the median values, cartilage provides the highest increase in ST pressure, followed by soft tissue. Although silicone is regarded as the material with the highest stiffness of the three materials considered in the present study, it shows the lowest efficiency for RWM reinforcement. We believe that the proper placement of the reinforcement materials that are in good contact with the RWM is crucial for a high and repeatable reinforcement effect. The relatively stiff silicone material makes it challenging to achieve this requirement.