Spoken letter recognition

Automatic recognition of spoken letters is one of the most challenging tasks in the field of computer speech recognition. The difficulty of the task is due to the acoustic similarity of many of the letters. Accurate recognition requires the system to perform fine phonetic distinctions, such as B vs. D, B vs. P, D vs. T, T vs. G, C vs. Z, V vs. Z, M vs. N and J vs. K. The ability to perform fine phonetic distinctions---to discriminate among the minimal sound units of the language---is a fundamental unsolved problem in computer speech recognition.