Background: The abrupt transition of a signal from off to on and vice versa typically produces spectral splatter that can mask other signals that are spectrally removed from the nominal signal frequency. Both the Miller and Licklider (1950) and Cherry (1953) studies of interrupted speech and alternated speech, respectively, acknowledged the generation of extraneous noise by the rapid on and off characteristics of their unshaped signals but noted for slower interruption rates (e.g., 10 interruptions per second); the masking effects were minimal. Recent studies of interrupted speech have avoided this issue by shaping the rise-fall times with a digital algorithm (e.g., Jin and Nelson, 2010; Wang and Humes, 2010). A second variable in the interrupted speech paradigm is the temporal location or placement of the interruptions (i.e., where in the waveform the interruptions occur). Here the issue is this: what parts of an utterance are necessary to enable intelligibility (e.g., Fogerty and Kewley-Port, 2009)? Interruptions may or may not disturb these necessary cues. Purpose: Here is the prompting question: do shaped and unshaped rise-fall characteristics of the on-segments of interrupted speech produce the same or different recognition performances? A second question arises: are recognition performances on complementary halves of an interrupted signal the same or different? Research Design: This study used a mixed-model design with two within-subject variables (unshaped and shaped rise-fall characteristic, complementary halves) and one between-subjects variable (listener group). Study Sample: A total of 12 young listeners (age range: 19-29 yr) with normal hearing and 12 older listeners (age range: 53-80 yr) with hearing loss for pure tones participated. Data Collection and Analysis: A total of 95 consonant-vowel nucleus-consonant words were interrupted (10 interruptions per second; 50% duty cycle) by parsing alternate 50 msec segments to separate files, which provided complementary temporal halves of the target word referenced to word onset; the first on-segment of the 0 msec condition started at word onset, whereas the first on-segment of the 50 msec condition started 50 msec after word onset. The interruption routine either applied no shaping of the 4 msec rise-fall times or a cos2 shape. Each listener received 25 practice words then a unique randomization of 280 interrupted words (70 words, 2 rise-fall shapes, and 2 interrupt onset conditions). Results: The listeners with normal hearing performed 8-16% better on the various comparable conditions than did the older listeners with hearing loss. The mean performance differences between shaped and unshaped rise-fall characteristics ranged from <1-3% and were not significant. Performance was significantly 10-17% better on the 0 msec condition than on the 50 msec condition. There was no significant interaction between the two main variables, rise-fall shape, and onset time of the interruptions. Conclusions: The rise-fall shape of the onset and offset of the on-segment of the interruption cycle does not affect recognition performance of words. The location of the interruptions in a word can have a significant effect on recognition performance.

OBJECTIVE: To determine in an interrupted word paradigm (Maryland CNCs; 10 ips, 50% duty cycle) if different locations of the interruption pattern produce different recognition performances. DESIGN: Repeated measures using two interruption patterns that were complementary halves referenced to word onset; one started with word onset (0-ms), the other started 50 ms later. The hypothesis was that recognition performance would be better on the 0-ms condition than on the 50-ms condition, but there would be some words with the reverse relation. STUDY SAMPLE: Twenty-four young adults with normal hearing for pure tones and 32 older adults (mean = 67 years) with sensorineural hearing loss participated. RESULTS: With the young listeners mean recognition performance on the 0-ms condition (63.1%) was significantly better than the mean performance on the 50-ms condition (47.8%). About twice as many words had better performance on the 0-ms condition. With the older listeners, who were given only stimuli on which performances were > 58% by the young normals, performances on the two conditions were the same. CONCLUSIONS: The hypothesis was supported with the young listeners. The equal performance by the older listeners on the two conditions was attributed to the manner in which the words were selected.