A computer-based environment for compression experiments with code sounds from the lexiphone
Willis Pittman Martin · cIRcle (University of British Columbia) · 2011
The Lexiphone is a reading machine for the blind which makes an optical to auditory transformation from the printed character to a sound code. This thesis is the development of a computer-based environment for studying the code. Fluctuations in the code signals generated by repeated scanning of the same ink pattern were studied using a Fourier analysis routine. From the Fourier coefficients representing these code signals it was established that the error in mean pitch of the code sound produced for the letter "s" is less than 1%. This error is typical for the alphabet and does not cause the blind user difficulty. The method of compressing the code signals is explained and studied with the aid of a Hadamard transform routine. This transform permits ready, comparison of compressed and uncompressed code signals. The results of direct comparisons between uncompressed code and compressed code are disappointing: the two presentations seem approximately equivalent. The reading rate in words per minute for a blind subject trained to read with the uncompressed code was not improved with the compressed code. A previous worker had found that the compressed code for letters was better discriminated and easier to learn. In. another experiment reported in the thesis six sighted subjects were used: three subjects were taught eight four-letter words presented in uncompressed code and the other three were taught the same words in a compressed version of the code. The learning curves for the two groups were approximately the same. Experimental time for subject testing was less than that used by the previous worker and suggestions are made for further experiments which may elucidate the problem of reading compressed code.