Sound can make a digital fabric feel rougher or smoother
In the FabSound study, researchers used mid-air ultrasound haptics to create the sensation of touching different fabric textures in mid-air—no physical fabric was present. When they manipulated the sound played during the touch, participants' judgments of roughness changed: rubbing sounds made the fabrics feel smoother, while pure tones at 450 Hz and 900 Hz made them feel rougher [2]. The effect was reported through qualitative interviews, meaning participants described their experiences in their own words rather than being scored on a numerical roughness scale.
This is a clear demonstration of audio-tactile integration: the tactile signal from the ultrasound device stayed the same, but the added sound changed how rough the texture felt. The direction of the effect matters—rubbing sounds pulled perception toward smoothness, while pure tones pulled it toward roughness—suggesting that the brain combines auditory and tactile cues rather than treating touch as a standalone sense.
Why would a sound change what your hand feels?
The FabSound results are consistent with the idea that the brain treats touch-related sound as extra information about a surface. When you touch a real fabric, the sound of rubbing carries clues about its roughness, so hearing a rubbing sound during a digital touch may bias the brain toward assuming a smoother surface [2]. Pure tones, by contrast, do not resemble natural fabric sounds and may be interpreted as a separate roughness cue, making the texture feel rougher [2].
The study also found that the rubbing sound of fabric evoked associations with soft materials and led to more calming experiences [2]. That emotional response is a separate observation from the roughness shift, but it suggests that audio-tactile integration in mid-air haptics is not only about physical properties like roughness—it can also shape the affective quality of a touch experience.
What mid-air ultrasound haptics bring to the question
Mid-air ultrasound haptics use focused sound waves to create pressure on the skin without any wearable device, which makes them useful for testing audio-tactile integration because the tactile signal can be precisely controlled while sound is added or changed independently [1][2]. The FabSound study exploited this by pairing controlled ultrasound haptic textures with manipulated audio, allowing the researchers to isolate the effect of sound on perceived roughness [2].
Other work on mid-air ultrasound haptics has focused on improving the tactile signal itself—for example, a new beamforming method can adjust the focal area by about 25–30%, allowing either more precise tactile localization or stronger radiation force [1]. That kind of control matters for audio-tactile research because it lets experimenters vary the tactile cue systematically while keeping the audio separate, though the beamforming study did not itself test audio integration [1].
The bigger picture: touch is not a single channel
The FabSound findings fit a broader pattern in which mid-air haptics is being combined with other sensory modalities. One system pairs ultrasound haptics with heated airflow to produce thermal and vibrotactile cues simultaneously, and users reported that the combined thermo-tactile feedback enhanced their experience [5]. That study did not test audio, but it reinforces the idea that haptic feedback in mid-air is often experienced as part of a multisensory whole rather than in isolation.
What remains less clear is how far the audio-tactile effect generalizes. The FabSound evidence comes from qualitative interviews about digital fabric textures, so it tells us that sound can shift roughness perception in that specific context [2], but it does not establish whether the same sound cues would change the perception of other haptic properties, such as shape or motion, or whether the effect would hold with different ultrasound haptic patterns. The practical takeaway for now is that designers of mid-air haptic experiences should treat sound as part of the tactile design, not as an afterthought.
Sources used in this answer
Tactile feedback in mid-air ultrasound haptics with adjustable spatial resolution
A new beamforming method for mid-air ultrasound haptics can adjust the acoustic focal area by roughly 25–30%, enabling either more precise tactile localization or stronger radiation force.
FabSound: Audio-Tactile and Affective Fabric Experiences Through Mid-air Haptics
In mid-air haptic simulations of fabric textures, rubbing sounds made textures feel smoother while pure tones at 450 Hz and 900 Hz made them feel rougher, and rubbing sounds were associated with soft materials and calming experiences.
Extended Mid-air Ultrasound Haptics for Virtual Reality
A robot-mounted ultrasound array can extend mid-air haptic feedback to room-scale virtual reality while preserving bare-hand interaction, and motion of the array did not noticeably affect users' perception.
AdapTics: A Toolkit for Creative Design and Integration of Real-Time Adaptive Mid-Air Ultrasound Tactons
A toolkit called AdapTics enables designers to create adaptive mid-air ultrasound tactons that can change at runtime, and it improved creativity support ratings for exploration and expressiveness in a study with 12 XR and haptic designers.
Mid-Air Thermo-Tactile Feedback using Ultrasound Haptic Display
A mid-air system combining ultrasound haptics with heated airflow can produce simultaneous thermal and vibrotactile cues, with warm and heat-pain detection thresholds similar to contact-based thermal thresholds, and thermo-tactile feedback enhanced user experience.