# Influence of Piano Key Vibration Level on Players' Perception and Performance in Piano Playing
## 3 Results  
### Influence of Vibration Levels on Perceived Instrument Sound, Control, and Feel  
In the analysis of the preference ratings (\"better\", \"worse\", or \"similar\"), a high variance and for some participants also controversial ratings were observed. We decided to present the ratings across all parts and participants here, because it was not possible to draw conclusions from the ratings per participant or per part. The result is presented in Figure 2.  
The high variance of the ratings in Figure 2 reflects the closeness of the key vibration levels to the limits of human perception. Additional factors that can have disturbed the ratings are the mood and fatigue of the player. Also a self-evaluation of the playing, the difficulty of the task, or the imposed expectation of a difference between the settings might have disturbed the ratings. However, a visual comparison of the mean values in Figure 2 indicates a tendency in the preference of the players toward vibration level \(V_{2}\). The preference of vibration level \(V_{2}\) is confirmed by the evaluation of the player's verbal self-reports presented hereafter. The free verbalizations were analyzed with an approach presented by [PERSON] et al. [12], where concepts by [PERSON] [13] were applied to musical instrument evaluation. Based on the context and for each participant, the meaning, category, and preference of each statement was identified via linguistic tools such as reformulations, propositions, and comparatives. Thereafter, the statements were classified into positive and negative statements for three categories: sound, control, and feel. Statements covering multiple categories were split before classification. Statements not indicating a preference or a perceived difference were counted as \"no difference\". Figure 2: Analysis of the preference ratings (“better” (1), “worse” (\(-\)1), or “similar” (0)) of the vibration levels across all parts and all participants. The ratings are based on direct comparisons between all pairs of levels. The ratings are relative. For example, a positive value for \(V_{0}\):\(V_{1}\) indicates a preference of \(V_{0}\) over \(V_{1}\) and a negative value a preference of \(V_{1}\) over \(V_{0}\). The shaded area marks the standard deviation of the ratings. The results are summarized in Table 1. Significance was evaluated with Pearson's \(\chi^{2}\)-tests at a confidence level of 95%. The test was performed on all statements (positive and negative) per category. Although we did not alter the sound throughout the experiment, Table 1 shows that the vibration levels \((V_{0},V_{1},V_{2},V_{3})\) have an influence on the pianists' sound perception. Pairwise testing with Bonferroni correction showed that the significance of the \(\chi^{2}\)-test in the sound category arises from the difference between \(V_{0}\) and \(V_{2}\). The phenomenon of vibrotactile feedback causing a difference in sound perception is known as integration of auditory and tactile information [14; 15; 16] or weak synesthesia [17]. The preference of \(V_{2}\) over \(V_{3}\), confirming the evaluation of the preference ratings in Figure 2, was surprising because vibration level \(V_{3}\) is closer to the levels of acoustic instruments (see Figure 1). An explanation lies in five statements about vibration level \(V_{3}\), which were classified as negative. These statements criticized the balance of the perceived sound as having \"too much bass\" or being \"unbalanced\". The results for control and feel are not significant according to the \(\chi^{2}\)-tests. For vibration level \(V_{1}\) there were twice as many \"no difference\" statements than for all other levels, which indicates that \(V_{1}\) is most difficult to differentiate. Only two participants consciously noticed a change in vibration levels during the experiment, when vibration level \(V_{3}\) was compared to \(V_{0}\) and vice versa. Both recognized the vibrations during the last part, when the keyboard was the focal point.