Hapbeat

Audio-Tactile Rendering: A Review on Technology and Methods to Convey Musical Information through the Sense of Touch

“…It was proposed that the ideal actuator should combine low-cost and lightweight design, good performance at low frequencies, and a balance between size and vibrotactile stimulation. VCAs and ERMs are the most used actuators (see Table 2 , Table 3 and Table 4 ) and new concepts such as the DMA [ 37 ] and the string-motor device [ 42 ] are being studied. However, there are other technologies like mid-air ultrasound haptic feedback that demonstrated to be effective for frequency discrimination tasks [ 81 ] and may be investigated for touchless applications to explore music in museums or music stores and avoid disease transmission, for instance.…”

“…Furthermore, enhancing performance of actuators at low frequencies is desirable as the frequency range for best perceptible vibrations is lower than that of audio. Innovations such as the string-motor actuator proposed in [ 42 ] allows to cover a wider area efficiently but effectiveness to render specific music features, such as melody or timbre, remains unclear. On the other hand, the DMA proposed in [ 37 ] allows complex signal mapping covering a smaller area, which suggests that balance between size and stimuli resolution is achievable.…”

“…Consequently, most works described in this section are not necessarily portable at the moment of publication, but have clear opportunities to lately become HMP-WDs. Starting from prototypes that cover a small skin surface, there are bracelets ( Figure 4 a), designed to be worn on the wrist (see, e.g., in [ 19 , 21 , 59 , 60 ]); gloves and mobile device mockups ( Figure 4 b), designed to be worn or held on the hands (see, e.g., in [ 37 , 61 , 62 , 63 , 64 ]); belts ( Figure 4 c), designed to be worn surrounding the body from the chest to the abdomen (see, e.g., in [ 8 , 35 , 41 , 42 ]); and jackets ( Figure 4 d), designed to be worn on the upper body with actuators usually located on the back, the front and the superior limbs (e.g., [ 38 , 65 ]). Other variations are whole body suits [ 15 ], and headphone type displays [ 39 ], but instances are scarce.…”

“…Strategies such as pulse-width modulation (PWM) for efficient signal rendering may be combined with lightweight efficient actuators such as DMAs; although resulting increased noise should be assessed [ 36 ]. Additionally, if it is expected that the user wears the HMP, the appearance and user interface capabilities of the device are relevant and should be considered, as they are in [ 35 , 42 , 65 ]. Finally, bone and airborne conduction should be considered for high frequency-energy vibrations or when HMP-WDs are attached near the head or internal organs, as may influence vibrotactile perception.…”

“…Belts and jackets are of particular consideration as they cover larger areas. Alternatively, Yamazaki et al [ 42 ] showed that larger areas of the body may be covered using strings attached to vibrating motors instead of using the motors themselves to convey the vibrotactile stimuli. This is an innovative implementation that results in better transmission of low frequency vibrations than that obtained with linear actuators.…”