Experiments on spectrogram reading

This paper presents the results of several spectrogram reading experiments that were designed to determine the amount of phonetic information that is contained in the speech signal. The task involved identifying the phonetic content of an unknown utterance only from a visual examination of the spectrogram. In the first experiment, one of the authors attempted to phonetically label spectrograms of normal and anomalous English utterances as well as words in a known carrier phrase. The results, when compared with the transcriptions of three phoneticians who listened to the utterances, indicated an overall agreement of better than 85% on the sentences, and 93% for words in a carrier phrase. In the second and third experiments, we investigated the speed at which spectrogram reading can be accomplished. In the final experiment, five students read spectrograms of normal English sentences after a 13-week course in acoustic phonetics. Working as a group, the class agreed with the transcribers on over 80% of the segments. Implications for speech recognition and aids for the deaf are discussed.