# A Review of Recent Literature on Audio-Based Pseudo-Haptics
## 2 The Review
### Audio-Based Pseudo-Haptics
In a similar experiment, [PERSON] et al. [42] also compared the perceived heaviness of two square buttons, although they now manipulated the sound's loudness instead of frequency. They found that louder sounds were perceived as being significantly heavier. Interestingly, the tail end of the sound appeared to play a critical role in the perceived heaviness: in comparison to the onset sound (initiation of sound), the tail end of the sound yielded significant results. By changing the visual and/or auditory stimuli, the researchers concluded that haptic feedback without the use of expensive haptic devices can be simulated. These series of studies confirmed the effectiveness of their method, indicating that the heaviness sensation conventionally induced by modulating visual feedback can also be created by modulating auditory feedback. [PERSON] and [PERSON] [55] explored the relationship between various sound parameters, and more specifically, pitch, waveform shape (square, sawtooth, triangle, and sine), attenuation duration, and artificial harmonics (sound generated by a second oscillator to enrich the sound produced) and material sensation. The study was comprised of seven experiments. Experiments 1 and 2 consisted of a trial to determine the range and the specific parameters used for the remaining five experiments. In Experiment 1, the participants were asked to listen to different tracks to determine the range of parameters required for the remaining experiments, and for those who succeeded, they were asked to judge whether the 22 sounds heard were percussive or not. Experiment 2 required the participants to describe the material they heard in the audio. Experiment 3 examined the effect of pitch on weight perception, where the participants were asked to rate the weight of six sounds with different pitches on a 5-point Likert scale. Experiment 4 examined the different waveforms at various pitches and their effect on roughness, where participants listened to 30 sounds (five waveforms evaluated at six different pitches) and ranked the \"prickliness\" of each sound on a 5-point Likert scale. Experiment 5 examined the effect of attenuated duration of different pitches on dampness. More specifically, participants evaluated 54 sounds (nine sounds with different attenuation times with six different pitches) and ranked dampness on a 5-point Likert scale. Experiment 6 explored the effect of combining different pitches and artificial harmonics on the perception of glossiness. Here, 11 sounds with different pitches and artificial harmonics were evaluated and ranked for glossiness on a 5-point Likert scale. The purpose of Experiment 7 was to test the feasibility of the results of the prior experiments. Participants were asked to match a sound to a picture of a material and explain their reasoning. In sum, 80 participants were recruited to participate in Experiments 1 and 3-6, while 100 participants were recruited to participate in Experiments 2 and 7. The results of Experiment 3 indicated that low-pitched sounds were perceived as heavier than higher-pitch sounds. Experiment 4 indicated that pink noise (sound that carries the same energy across each octave) maintained its perceived roughness sensation at different pitches. Moreover, the relative roughness of square and sawtooth waveforms appeared to decrease as pitch increased, whereas the perceived roughness of the triangle and sine waveforms remained relatively constant regardless of the pitch. The results of Experiment 5 revealed a correlation between attenuation time, pitch, and dampness sensation, with lower frequencies and shorter attenuation durations increasing the perception of dampness. Experiment 6 showed that pitch influenced the perception of glossiness, and despite participants having trouble identifying changes in artificial harmonics (sound enrichment), they believed that increasing the artificial harmonic pitch enhanced the perceived glossiness. Experiment 7 tested the validity of the previous six experiments.