A reliable non-verbal vocal input metaphor for clicking

While experiencing an immersive virtual environment a suitable trigger metaphor is often needed, e.g. for the interaction with objects out of physical reach or system control. The BlowClick approach [35] that is based on non-verbal vocal input has been proven to be a valuable trigger technique in previous work. However, its original detection method is vulnerable to false positives and, thus, is limited in its potential use. Therefore, we extended the existing approach by adding machine learning methods to reliably classify blowing events. We found a support vector machine with Gaussian kernel performing the best with at least the same latency and more precision than before. Furthermore, we added acoustic feedback to the NVVI trigger, which increases the user's confidence and whose absence was also stated as a limitation of the previous work. With this extended technique, we repeated the conducted Fitts' law experiment with 33 participants and could confirm that it is possible to use NVVI as a reliable trigger as part of a hands-free point-and-click interface. Furthermore, we tested reaction times to measure the trigger's performance without the influence of pointing and calculated device throughputs to ensure comparability.