Natural Fast Speech Research Articles

Neural oscillations track natural but not artificial fast speech: Novel insights from speech-brain coupling using MEG

Neural oscillations contribute to speech parsing via cortical tracking of hierarchical linguistic structures, including syllable rate. While the properties of neural entrainment have been largely probed with speech stimuli at either normal or artificially accelerated rates, the important case of natural fast speech has been largely overlooked. Using magnetoencephalography, we found that listening to naturally-produced speech was associated with cortico-acoustic coupling, both at normal (∼6 syllables/s) and fast (∼9 syllables/s) rates, with a corresponding shift in peak entrainment frequency. Interestingly, time-compressed sentences did not yield such coupling, despite being generated at the same rate as the natural fast sentences. Additionally, neural activity in right motor cortex exhibited stronger tuning to natural fast rather than to artificially accelerated speech, and showed evidence for stronger phase-coupling with left temporo-parietal and motor areas. These findings are highly relevant for our understanding of the role played by auditory and motor cortex oscillations in the perception of naturally produced speech.

Effectiveness of pauses inserted in natural fast speech in Cochlear Implant and Hearing Aid Users.

Effectiveness of pauses inserted in natural fast speech in Cochlear Implant and Hearing Aid Users.

Speech perception of Natural Fast Speech by Cochlear Implant and Hearing Aid Users

Speech perception of Natural Fast Speech by Cochlear Implant and Hearing Aid Users

Effect of Speaking Rate on Recognition of Natural fast Speech by Cochlear Implant Users

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Natural fast speech is perceived as faster than linearly time-compressed speech.

Listeners compensate for variation in speaking rate: In a fast context, a given sound is interpreted as longer than in a slow context. Experimental rate manipulations have been achieved either through linear compression or by using natural fast speech. However, in natural fast speech, segments are subject to processes such as reduction or deletion. If speaking rate is then defined as the number of segments per unit time, the question arises as to what impact such processes have on listeners' normalization for speaking rate. The present study tested the effect of sentence duration and fast-speech processes on rate normalization for a German vowel duration contrast. Results showed that a naturally produced short sentence containing segmental reductions and deletions led to the most "long" vowel responses whereas the long sentence with clearly articulated segments led to the fewest. This suggests that speaking rate is not merely calculated as the number of segments realized per unit time. Rather, listeners associate properties of natural fast speech with a higher speaking rate. This contrasts with earlier results and a second experiment in which perceived speaking rate was measured in an explicit task. Models of speech comprehension are evaluated with regard to the present findings.

De verstaanbaarheid van natuurlijk snelle versus kunstmatig versnelde spraak in het Nederlands

The debate whether natural fast speech is more intelligible than artificially time-compressed speech has not clearly been answered yet. For Dutch, for instance, it has been shown in a phoneme detection task that time-compressed speech is more intelligible than natural fast speech, while for Danish listeners, no difference between the intelligibility of natural fast speech and time-compressed speech was reported from a dictation task. This article further investigates these conflicting results by reporting on a dictation task with Dutch listeners. The results suggest that the reported differences are more likely to be language-related than task-related.

Perceptual learning of time-compressed and natural fast speech

Speakers vary their speech rate considerably during a conversation, and listeners are able to quickly adapt to these variations in speech rate. Adaptation to fast speech rates is usually measured using artificially time-compressed speech. This study examined adaptation to two types of fast speech: artificially time-compressed speech and natural fast speech. Listeners performed a speeded sentence verification task on three series of sentences: normal-speed sentences, time-compressed sentences, and natural fast sentences. Listeners were divided into two groups to evaluate the possibility of transfer of learning between the time-compressed and natural fast conditions. The first group verified the natural fast before the time-compressed sentences, while the second verified the time-compressed before the natural fast sentences. The results showed transfer of learning when the time-compressed sentences preceded the natural fast sentences, but not when natural fast sentences preceded the time-compressed sentences. The results are discussed in the framework of theories on perceptual learning. Second, listeners show adaptation to the natural fast sentences, but performance for this type of fast speech does not improve to the level of time-compressed sentences.

Word perception in fast speech: artificially time-compressed vs. naturally produced fast speech

Natural fast speech differs from normal-rate speech with respect to its temporal pattern. Previous results showed that word intelligibility of heavily artificially time-compressed speech could not be improved by making its temporal pattern more similar to that of natural fast speech. This might have been due to the extrapolation of timing rules for natural fast speech to rates that are much faster than can be attained by human speakers. The present study investigates whether, at a speech rate that human speakers can attain, artificially time-compressed speech is easier to process if its timing pattern is similar to that of naturally produced fast speech. Our first experiment suggests, however, that word processing speed was slowed down, relative to linear compression. In a second experiment, word processing of artificially time-compressed speech was compared with processing of naturally produced fast speech. Even when naturally produced fast speech is perfectly intelligible, its less careful articulation, combined with the changed timing pattern, slows down processing, relative to linearly time-compressed speech. Furthermore, listeners preferred artificially time-compressed speech over naturally produced fast speech. These results suggest that linearly time-compressed speech has both a temporal and a segmental advantage over natural fast speech.

Word-level intelligibility of time-compressed speech: prosodic and segmental factors

In this study we investigate whether speakers, in line with the predictions of the Hyper- and Hypospeech theory, speed up most during the least informative parts and less during the more informative parts, when they are asked to speak faster. We expected listeners to benefit from these changes in timing, and our main goal was to find out whether making the temporal organisation of artificially time-compressed speech more like that of natural fast speech would improve intelligibility over linear time compression. Our production study showed that speakers reduce unstressed syllables more than stressed syllables, thereby making the prosodic pattern more pronounced. We extrapolated fast speech timing to even faster rates because we expected that the more salient prosodic pattern could be exploited in difficult listening situations. However, at very fast speech rates, applying fast speech timing worsens intelligibility. We argue that the non-uniform way of speeding up may not be due to an underlying communicative principle, but may result from speakers’ inability to speed up otherwise. As both prosodic and segmental information contribute to word recognition, we conclude that extrapolating fast speech timing to extremely fast rates distorts this balance between prosodic and segmental information.