# A Review of Recent Literature on Audio-Based Pseudo-Haptics
## 2 The Review
### Audio-Haptic Interactions
Eight participants were tasked with interacting with various surface textures under three feedback conditions: (i) audio only, (ii) haptic only, and (iii) audio-haptic combination. The results indicated that the participants were able to identify textures most accurately in the presence of both auditory and haptic cues. The authors concluded that realistic feedback synthesized from virtual objects can enhance virtual environments through visual, auditory, and haptic interactions. Motivated by the limitations in the perception of graphical information by the visually impaired and the need to substitute the sense of sight with other senses, [PERSON] et al. [53] describe a tablet-based method that presents visual information in the form of a \"tactile picture\" that incorporates haptic and audio cues to provide contextually selected information. Tactile pictures incorporate raised lines and elevated surfaces that are detectable under the user's fingers. Although there are guidelines/recommendations regarding the size, shape, and spacing of the lines and elevated surfaces, there are shortcomings with the approach. To help overcome these shortcomings, [PERSON] et al. [53] include auditory cues in the form of speech-based descriptions of the tactile picture (printed with a braille printer placed on the tablet screen) to complement the tactile cues. A user study found that the accompanying auditory descriptions improve the understanding and interpretation of the information presented by the tactile picture. Results also revealed that these descriptions should be 5 to 10 s in duration; when this duration was exceeded, the message was incomprehensible [53]. This section focused on studies that examined the interaction between auditory and haptic feedback using a form of haptic device. Sound can significantly enhance the perception of haptic feedback by providing additional cues that complement the tactile sensations. As described above, auditory stimuli can amplify the realism and intensity of haptic feedback, making virtual interactions feel more authentic. For instance, the sound of an object being manipulated in a virtual environment can reinforce the perceived texture, weight, and resistance of that object, leading to a more cohesive sensory experience (see [33]). This synergy between auditory and haptic feedback is crucial for applications ranging from virtual reality simulations to teleoperation systems, where the fidelity of sensory inputs can affect user performance and satisfaction. Moreover, the temporal synchronization between sound and haptic cues plays a pivotal role: any discrepancy can disrupt the user's sense of presence and immersion. Therefore, understanding and leveraging the interplay between sound and haptic perception is essential for developing more effective and engaging virtual environments. The influence of sound on haptic perception in virtual environments is a nuanced area of research that underscores the multisensory integration fundamental to immersive experiences. In the subsequent section, we explore the use of auditory feedback to induce pseudo-haptic sensations.