Tactile displays are now becoming available in a form that can be easily used in a user interface. This paper describes a new form of tactile output. Tactons, or tactile icons, are structured, abstract messages that can be used to communicate messages non-visually. A range of different parameters can be used for Tacton construction including: frequency, amplitude and duration of a tactile pulse, plus other parameters such as rhythm and location. Tactons have the potential to improve interaction in a range of different areas, particularly where the visual display is overloaded, limited in size or not available, such as interfaces for blind people or in mobile and wearable devices. This paper describes Tactons, the parameters used to construct them and some possible ways to design them. Examples of where Tactons might prove useful in user interfaces are given.

Tactons: Structured Tactile Messages for Non-Visual Information Display

Tactile displays are now becoming available in a form that can be easily used in a user interface This paper describes a new form of tactile output Tactons, or tactile icons, are structured, abstract messages that can be used to communicate messages non-visually A range of different parameters can be used for Tacton construction including: frequency, amplitude and duration of a tactile pulse, plus other parameters such as rhythm and location Tactons have the potential to improve interaction in a range of different areas, particularly where the visual display is overloaded, limited in size or not available, such as interfaces for blind people or in mobile and wearable devices This paper describes Tactons, the parameters used to construct them and some possible ways to design them Examples of where Tactons might prove useful in user interfaces are given

/pdf/tactons-structured-tactile-messages-for-non-visual-3v7qh1p21c.pdf

Tactons: structured tactile messages for non-visual information display

Objective: This article provides an overview of tactile displays. Its goal is to assist human factors practitioners in deciding when and how to employ the sense of touch for the purpose of information representation. The article also identifies important research needs in this area. Background: First attempts to utilize the sense of touch as a medium for communication date back to the late 1950s. For the next 35 years progress in this area was relatively slow, but recent years have seen a surge in the interest and development of tactile displays and the integration of tactile signals in multimodal interfaces. A thorough understanding of the properties of this sensory channel and its interaction with other modalities is needed to ensure the effective and robust use of tactile displays. Methods: First, an overview of vibrotactile perception is provided. Next, the design of tactile displays is discussed with respect to available technologies. The potential benefit of including tactile cues in multimodal inte...

Tactile displays: guidance for their design and application.

http://www.nano-micro.gr/papers/Chouvardas_2008_Displays.pdf

Tactile displays: Overview and recent advances

In this work, the tactual information transmission capabilities of a tactual display designed to provide stimulation along a continuum from kinesthetic movements to cutaneous vibrations are assessed. The display is capable of delivering arbitrary waveforms to three digits (thumb, index, and middle finger) within an amplitude range from absolute detection threshold to about 50 dB sensation level and a frequency range from dc to above 300 Hz. Stimulus sets were designed at each of three signal durations (125, 250, and 500 msec) by combining salient attributes, such as frequency (further divided into low, middle, and high regions), amplitude, direction of motion, and finger location. Estimated static information transfer (IT) was 6.5 bits at 500 mseC., 6.4 bits at 250 mseC., and 5.6 bits at 125 msec. Estimates of IT rate were derived from identification experiments in which the subject’s task was to identify the middle stimulus in a sequence of three stimuli randomly selected from a given stimulus set. On the basis of the extrapolations from these IT measurements to continuous streams, the IT rate was estimated to be about 12 bits/seC., which is roughly the same as that achieved by Tadoma users in tactual speech communication.

/pdf/information-transmission-with-a-multifinger-tactual-display-4qkk52lvlt.pdf

Information transmission with a multifinger tactual display.

Experiments have been carried out to investigate the information transfer available via a single vibrator on the fingertip. In a first experiment, for stimuli with durations 80 to 320 ms, discrimination of a one-octave step change in frequency at the halfway point was investigated. Results were similar for three stimulus types--sinewave, monophasic pulse and tetraphasic pulse--suggesting temporal cues are more important than spectral cues in this task. In a second experiment, subjects were required to perceive changes in a sequence of stimulus elements. A presentation rate of 6.25 elements s-1 was found to give better results than a rate of 12.5 elements s-1. In the former case, the potential information transfer per element was estimated to be approximately 1.0 bits, corresponding to an information transfer rate of around 6 bits s-1. Implications for the design of a tactile aid to lipreading are discussed.

Information from time-varying vibrotactile stimuli.

Two experiments on the discrimination of time-varying tactile stimuli were performed, with comparison of stimulus delivery to the distal pad of the right index finger and to the right wrist (palmar surface). Subjects were required to perceive differences in short sequences of computer-generated stimulus elements (experiment 1) or differences in short tactile stimuli derived from a speech signal (experiment 2). The pulse-train stimuli were distinguished by differences in frequency (i.e., pulse repetition rate) and amplitude, and by the presence/absence of gaps (approximately 100-ms duration). Stimulation levels were 10 dB higher at the wrist than at the fingertip, to compensate for the lower vibration sensitivity at the wrist. Results indicate similar gap detection at wrist and fingertip and similar perception of frequency differences. However, perception of amplitude differences was found to be better at the wrist than at the fingertip. Maximum information transfer rates for the stimuli in experiment 1 were estimated at 7 bits s(-1) at the wrist and 5 bits s(-1) at the fingertip.

Tactile information transfer: A comparison of two stimulation sites

To establish the best strategy for transmitting speech‐derived information via a single tactile channel, measurements were made on the perception of frequency‐ and/or amplitude‐modulated pulse‐train stimuli, with a comparison of the electrotactile and vibrotactile modalities. In one experiment, vibrotactile perception of 2‐oct step changes in stimulus frequency was found to be significantly better than electrotactile on a timescale appropriate for the transmission of speech features (e.g., with practiced subjects, information transfer of 69% with 200‐ms vibrotactile stimuli, 32% with 200‐ms electrotactile stimuli). Perception of step changes in stimulus amplitude was similar in the two modalities when changes in amplitude were tailored to match the different dynamic ranges available. In a second experiment, vibrotactile perception of voice fundamental frequency with various codings was investigated. Both experiments showed information transfer for vibrotactile stimuli to be greater when frequency and amplitude modulation were used together rather than with one or the other in isolation (sentence‐stress identification scores: 66% for FM stimuli, 69% for AM stimuli, 80% for FM/AM stimuli). It is concluded that frequency‐ and amplitude‐modulated vibratory stimulation is a good choice in a practical device for the profoundly hearing impaired.

Vibrotactile and electrotactile perception of time‐varying pulse trains

Objective: This study investigated the effect of electrode configuration, stimulus rate, and EEG rejection level on the efficiency of ABR testing in babies. Design: ABR to click stimuli at 40 dB nHL were simultaneously recorded from two electrode configurations, ipsilateral mastoid to high forehead (Mi-Fh) and nape to high forehead (N-Fh), with two EEG rejection levels (± 5 μV and ± 10 μV). Stimulus rates were between 39.1 and 69.1 per second. Efficiency was measured by confidence in the ABR for a given test time. Study sample: Thirty babies who had passed a targeted newborn hearing screen with ABR thresholds ≤ 40 dB nHL. Results: The N-Fh configuration, as expected, gave on average a larger response amplitude compared to the Mi-Fh configuration but was only marginally significantly better in terms of test efficiency. There was no significant effect of stimulus rate on test efficiency between 39.1/s and 59.1/s. The lower ± 5 μV EEG rejection level was more test efficient. Conclusions: This study p...

ABR in newborns: Effects of electrode configuration, stimulus rate, and EEG rejection levels on test efficiency

Objective: This study set out to determine the accuracy with which tone pip ABR and click ABR, carried out in babies referred from universal newborn hearing screening, is able to predict the hearing outcome as determined by follow-up hearing tests. Study sample: The cohort of babies studied were all babies referred for hearing assessment from the universal newborn hearing screen in Sheffield, UK for the period January 2002 to September 2007, who were found to have a significant hearing impairment. Design: The results of hearing assessment following referral from the newborn hearing screen were collected together with those of follow-up tests carried out up to an age when behavioural testing had established ear- and frequency-specific thresholds at 0.5, 1, 2 and 4 kHz. Results: The standard deviation of the difference between the follow up and the tone pip ABR thresholds was 10.5 dB for the 4-kHz tone pip, 16.8 dB for the 1-kHz tone pip, and ranged between 21.7 and 24.7 dB for click ABR. Conclusion...

Denise A. Gratton

Papers

Information from time-varying vibrotactile stimuli.

Tactile information transfer: A comparison of two stimulation sites

Vibrotactile and electrotactile perception of time‐varying pulse trains

ABR in newborns: Effects of electrode configuration, stimulus rate, and EEG rejection levels on test efficiency

Predictive value of hearing assessment by the auditory brainstem response following universal newborn hearing screening