Interaction between segmental and nonsegmental factors in speech recognition

The present study demonstrates that spectrograms of Swedish utterances can be read with great accuracy under nontrivial conditions. This result is to be attributed primarily to the development of a formalized strategy that was designed to make it possible for spectrogram readers to derive information on certain grammatical features of an utterance such as word class, word boundaries, endings, and function elements. The input to this strategy consists of segmental phonetic features that the subjects extract from the spectrographic display and of information on prosodic features such as stress and tonal accent. The latter information is specified on the spectrogram for each syllable. An experimental situation is thus created that differs from the informal recognition of unknown utterances from spectrograms. A subject can base his final identification of lexical items not only on segmental phonetic features but also on an error-free specification of prosodic features and, in so far as he has been able to use the strategy successfully, on grammatical information. Experimental results are reported indicating that subjects improve their performance markedly with the aid of the strategy. In conclusion, attention is drawn to the important role that grammar and prosody appear to play in the present experiments and to the implications of the findings for future work on automatic speech recognition and speech perception.