When walking on paths, blind impressions of smelling, feeling and, above all, of hearing are evaluated. They serve navigation as a basis for orientation. Marked smells attract the attention of blind people. If someone knows that a fish shop is located in the immediate vicinity of the traffic lights, he deliberately looks for the traffic light post as soon as he notices the corresponding smell. Impressions of the feeling provide the blind with further information. Muscle and tendon sensations, for example, reveal that one leaves or enters the citizen dough. Exposed changes in the subsoil (asphalt, sand path, paving stones …) often form landmarks. Heat sensations on the skin, e.g. By solar irradiation, can be used in the direction determination. Pain sensations illustrate the existence of obstacles. Noises are the most important orientation aid. Humans can evaluate three kinds of sound: what emanates sounds is “Urschall”.
If another vibration is caused by the vibration of one object, this is referred to as the “sound”. Sound is reflected by objects. The evaluation of this “reverberation” allows the detection of obstacles and is called “echo-localization” . By means of echolocalisation, under favorable circumstances, obstacles can be found from a distance of more than five meters when reaching at least knee height. Blind people mainly use the changes of the cadence, especially in the frequency range from 800 to 4000 Hz. Rarely, however, they hear the frequency change consciously; Often they feel a feeling of pressure at the site of the skin that would hurt when they collide with the obstacle. The closer they get to the obstacle, the stronger the sensation of echolocalization. Anyone who is well-versed in the acoustical places can determine the direction and distance of obstacles and make statements on the hardness of their material.
The sounds and the place where they originate form the “network” of the room . Direction and distance of the primary sound occurring in road traffic show e.g. Where the road is located, and where the next cross-road branches off. Audio networks make it possible to distinguish between landscapes, such as forests or fields, and the recognition of known roads. The same primary sound causes characteristic churning and rewinding in different environments. The step noise “breaks” in a narrow alley on the walls, “runs” in an empty place “into the void” and “relapses” in a station hall. Listening to noise from the same place in the listening network always forms “dimensional deviations” . They help in direction and distance determination. Examples are music from a restaurant or the working noise of a company. However, the path or environment-typical radio network is subject to random and systematic changes. If there is no music at random, or is not worked on Sundays during operation, the corresponding measure is omitted. The blind person must then find substitute marks for location determination.
- Strategies of Orientation
In order to link and pass on the multimodal information, blind driving descriptions are provided in the sense of cognitive running cards. Their descriptions are considerably more detailed than those of the seer. In doing so, they describe decision-making points and risky waypoints particularly thoroughly. Regularities of our developed environment are learned in the form of “environmental schemata” . Blind people frequently resort to suspicious situations in a strange environment. This is illustrated by the example of the first figure. If a blind person at an unknown intersection regularly hears recurring changes of the traffic flow, the assumption of a traffic-controlled intersection is approximate. There are several subordinate schemes. By carefully listening to the traffic flow of the intersecting roads, he must recognize the correct scheme. The schemata help him to classify his perceptions correctly, and to behave cordingly.
A blind is near the crossroads of X and Y roads in the quadrant (X +, Y -) on B1. It crosses the X-road to get into the quadrant (X +, Y +). Part (a) shows the simplest case: both roads are two-lane. The blind can cross and reach target Z as soon as the traffic of the right-hand lane of the Y-road flows along the line (X 0, Y-). In part (b), the X road is three-lane, and it has a traffic island. First, the track must be crossed in front of the traffic island – the blind must reach B2. This is possible when the traffic of the X road begins to flow behind the traffic island. On the second part of the crossing is the scheme of part (a).