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Converter From Visual Curves to Auditory Cues for Blind Persons

IP.com Disclosure Number: IPCOM000035030D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 15K

Publishing Venue

IBM

Related People

Mostow, MA: AUTHOR

Abstract

Disclosed is an invention which allows blind persons to "visualize" graphs, curves and simple drawings, either on paper or on a computer screen. It converts the picture into a sequence of tones which conveys the information in the picture in an intuitive way. This invention has two aspects: a concept and an implementation. The concept is to convert a simple line drawing, such as a graph, curve, or simple diagram, into a sequence of tones at different pitches in such a way that a blind person can "hear" the shape of the lines and curves. As one scans a vertical line across the picture from left to right, the height of each intersection of the scan line with the picture is converted into a tone whose frequency depends on the height, that is, on the y coordinate of the point.

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Converter From Visual Curves to Auditory Cues for Blind Persons

Disclosed is an invention which allows blind persons to "visualize" graphs, curves and simple drawings, either on paper or on a computer screen. It converts the picture into a sequence of tones which conveys the information in the picture in an intuitive way.

This invention has two aspects: a concept and an implementation. The concept is to convert a simple line drawing, such as a graph, curve, or simple diagram, into a sequence of tones at different pitches in such a way that a blind person can "hear" the shape of the lines and curves. As one scans a vertical line across the picture from left to right, the height of each intersection of the scan line with the picture is converted into a tone whose frequency depends on the height, that is, on the y coordinate of the point. The conversion from y coordinate to tone frequency is an exponential one, made so that the lowest recordable y coordinate corresponds to the lowest audible frequency, the highest to the highest, and a fixed vertical separation of points, no matter where they are located, corresponds to a fixed musical interval between the corresponding tones. For example, if a point with y coordinate -5 is heard as a tone at C below middle C, and a point with y = 0 is heard as middle C, then a point at y = 5 is heard as C above middle C. The precise mathematical transformation law from vertical coordinate y to frequency freq is given by: freq = a * exp(b*y), where a and b are chosen to satisfy min freq = a * exp(b*ymin) and max freq = a * exp(b*ymax). When the vertical scan line is moved at a constant rate from left to right, the shape of the curve or curves is "heard" by the direction and rate of change of the audible tone. For example, a horizontal line is heard as a constant tone, with a higher line corresponding to a higher tone and the musical interval between two tones being proportional to the distance between two horizontal lines. A vertical line is heard as a momentary noise in all frequencies simultaneously. A sloped line is heard as a pitch which rises or falls at a constant rate. For a fixed scan speed, the slope of a line is proportional to the rate of change of the pitch. A parabola is heard as a pitch which starts high, falls rapidly at first, falls at an ever-decreasing rate until it reaches its lowest pitch, then increases slowly and then faster and faster. A sine wave is heard as a pitch which oscillates up and down. The frequency and amplitude of a sine wave are heard by the speed and extent of rising and falling of the pitch. Experiments on human subjects, using a hand-held calculator with a "beep" of programmable pitch, show that a person easily distinguishes curves by their sounds. For example, the graph of y = (x squared) and y = (absolute value of x) are easily distinguished by the variable rate of change of the former compared to the const...