The Audioclouds project led to the development of a number of guidlines for design in a
range of areas concerned with mobile systems, concerning the gestural interfaces, intertial sensing, and audio interfaces. These are outlined below:
- Where uncertainty is present in an interactive system, the full uncertainty should be preserved as far as possible and the inference done on the complete distribution of potential values when an action must be performed. Early, irreversible, filtering of the values to sequentialise the process should be avoided.
- Uncertainty in an interface should be displayed to the user wherever it is relevant; doing so can regularise their behaviour in a natural manner. Granular synthesis provides a clean way of doing this in audio. Point cloud displays can be used for visual display.
- Designers should take careful note of delays that will be present in interacting with a system
and should employ predictive displays to mitigate the effect of such delays, wherever possible. Such displays should taken into account the certainty of the model and the sensor readings upon which they are based.
- When introducing ``intelligence'' into an interface, the flow of the underlying control process should not be disrupted. Creating a stable dynamic system which the user interacts with -- whose parameters are influenced by the higher level inference -- can be used to achieve this.
- Designers should ensure that decisions are only made when sufficient evidence has accumulated to support them, and that the arrival of such evidence does not violate the input bandwidth limitations in the joint human-computer loop. Systems which fail to do this will degrade poorly with reductions in control quality.
- Where asymmetric control loops exist (with system output bandwidth
exceeding input bandwidth) selection can be performed by providing statistically independent stimuli,
and testing for behaviour compatible with controlling those stimuli;
this applicable to many sensor and display types.
- Both in standing and in mobile situations, providing feedback marked spatial audio elements will improve interaction performance and will not affect perceived workload or walking speed. This is true for both egocentric and exocentric interfaces.
- Target size in an egocentric display controlled by pointing using the hand of a standing user should be more than 20°.
- When keeping contact with the real world audio environment is important, designers should consider the possibility of monaural or bone conductance presentation of the display. In the latter case, interaction speed and accuracy should remain the same. In the former, there is a decrease on interaction speed by a factor of 2.
- Natural options of browsing a real time updated virtual auditory environment, such as head movements, are preferred by users.
- Increasing the number of display elements will not significantly influence interaction performance in familiar egocentric displays as long as no intelligibility problems appear. In exocentric displays, however, because of the higher cognitive load imposed by the real time updated localization cues, increasing the number of display elements affects interaction speed in a negative way.
- When selecting a feedback marked spatial audio element using a stylus operated touch tablet 9° around the target should result in 70.7% selection success rate. This number becomes 16° and 18.5° for selecting using the hand and head of the user respectively. In the hand case, this number refers to selections in front of the user.
- A designer should not rely on a loudness based cue to deliver directional information. Such a cue is useful in improving intelligibility rates however, its success as a directional cue is limited.
- Designers should expect an approximately 20% deterioration of performance when people using their system are mobile. They could compensate by accordingly increasing target widths in the system.
- When possible, designers should allow for display size to grow, increasing target width since its effect is beneficiary from an accuracy point of view, and its effect is more important than that of distance.