A study of spatial perception using an ultrasonic guidance system

If a person does not have vision, he can only know his orientation in space using other sensory modalities. The hypothesis in this study was that the observer could recover spatial information about interior architectural surfaces from the use of an ultrasonic device. The observer obtained the distance information from the sound pattern (loudness) and the direction information from the proprioception when using an ultrasonic guidance system. Three features of architectural surfaces (slants, corners, and openings) were simulated in laboratory. Psychophysical methods were used to evaluate the capabilities of surface discrimination.

The two-alternative choice paradigm was used to examine if subjects could acquire spatial information using the device. Results showed that subjects could gain spatial information to discriminate a slant, a convexity/concavity, and an opening size.

Among the three psychophysical methods (the methods of constant stimuli, of limits, and of adjustment), the method of constant stimuli was chosen to evaluate the resolution limits in surface discrimination because this method provided the best compromises for the study situation.

The second experiment was conducted to evaluate the resolution limit of the subjects in terms of just noticeable differences (JND). The overall mean JNDs of 8 subjects in slant discrimination was 5.7 degrees. The overall mean JNDs in corner discrimination was 9.2 degrees. The mean JNDs in opening size discrimination were 3.2 inches for narrower sizes and 5.3 inches for wider sizes at 4.5 feet.

The measured JNDs document that the observers have the necessary capability for spatial orientation in an ordinary room. However, the sufficient capability for performing in real environment needs to be studied further. The study results are applicable to the areas of rehabilitation, industry and military: such as the design of aids for visually handicapped, the remote sensing of nonvisual surfaces, etc. The results may also benefit human factors researchers because they tell how well human can integrate the auditory and proprioceptive information.