Sufficient Time-Frequency Resolution for Reproducing Vibrotactile Sensation

In vibrotactile stimuli, it is essential to reproduce realistic tactile sensations to enhance the immersiveness of applications. To reproduce more realistic tactile experiences, various tools have been proposed to fine-tune and design vibrotactile sensations. Considering the situation where users adjust parameters manually, providing tactile sensations with fewer parameters is desirable. This study examines the coarsest resolution in the time and frequency dimensions necessary to present tactile sensations as realistic as vibrations recorded by the sensor. Time and frequency are fundamental parameters to express vibrations as a spectrogram, and we considered it important to investigate how much coarser the resolution could be without changing perception. We focus on the textural vibrations and the preliminary experiment compared actual texture vibrations with the reconstructed vibration as coarse as possible in the frequency dimension. The result showed that the frequency resolution above 172 Hz makes it difficult to distinguish between the vibrations. The main experiment, a similar discrimination experiment, verified the time resolution using the averaging filter of vibration intensity over time. The results indicate that with the update interval set to 30 ms, the discrimination rate compared to the original vibration is approximately 60%. This percentage is below the chance level of 75%, indicating that distinguishing between the two is difficult. Based on our experiments, it is necessary to have a frequency resolution of at least 172 Hz and a time resolution that updates intensity at a rate of 30 fps or higher to recreate tactile sensations comparable to actual vibrations.