Effects of the Carrier Phrase on Word-Recognition Performances by Younger and Older Listeners Using Two Stimulus Paradigms

Abstract

Background: In the 1950s, with monitored live voice testing, the vu meter time constant and the shortdurations and amplitude modulation characteristics of monosyllabic words necessitated the use of the carrierphrase amplitude tomonitor (indirectly) the presentation level of the words. This practice continues withrecorded materials. To relieve the carrier phrase of this function, first the influence that the carrier phrasehas on word recognition performance needs clarification, which is the topic of this study.<br />Purpose: Recordings of Northwestern University Auditory Test No. 6 by two female speakers were usedto compare word recognition performances with and without the carrier phrases when the carrier phraseand test word were (1) in the same utterance stream with the words excised digitally from the carrier (VA-1speaker) and (2) independent of one another (VA-2 speaker). The 50-msec segment of the vowel in thetarget word with the largest root mean square amplitude was used to equate the target word amplitudes.<br />Research Design: A quasi-experimental, repeated measures design was used.<br />Study Sample: Twenty-four young normal-hearing adults (YNH; M = 23.5 years; pure-tone average[PTA] = 1.3-dB HL) and 48 older hearing loss listeners (OHL; M = 71.4 years; PTA = 21.8-dB HL) participatedin two, one-hour sessions.<br />Data Collection and Analyses: Each listener had 16 listening conditions (2 speakers 3 2 carrier phraseconditions 3 4 presentation levels) with 100 randomized words, 50 different words by each speaker.Each word was presented 8 times (2 carrier phrase conditions 3 4 presentation levels [YNH, 0- to24-dB SL; OHL, 6- to 30-dB SL]). The 200 recorded words for each condition were randomized as 8,25-word tracks. In both test sessions, one practice track was followed by 16 tracks alternated betweenspeakers and randomized by blocks of the four conditions. Central tendency and repeated measuresanalyses of variance statistics were used.<br />Results: With the VA-1 speaker, the overall mean recognition performances were 6.0% (YNH) and 8.3%(OHL) significantly better with the carrier phrase than without the carrier phrase. These differences werein part attributed to the distortion of some words caused by the excision of the words from the carrierphrases. With the VA-2 speaker, recognition performances on the with and without carrier phrase conditionsby both listener groups were not significantly different, except for one condition (YNH listeners at8-dB SL). The slopes of the mean functions were steeper for the YNH listeners (3.9%/dB to 4.8%/dB) thanfor the OHL listeners (2.4%/dB to 3.4%/dB) and were <1%/dB steeper for the VA-1 speaker than for theVA-2 speaker. Although the mean results were clear, the variability in performance differences betweenthe two carrier phrase conditions for the individual participants and for the individual words was strikingand was considered in detail.<br />Conclusion: The current data indicate that word recognition performances with and without the carrierphrase (1) were different when the carrier phrase and target word were produced in the same utterancewith poorer performances when the target words were excised from their respective carrier phrases(VA-1 speaker), and (2) were the same when the carrier phrase and target word were produced as independentutterances (VA-2 speaker).<br />See the Supplementary Data tab for supplementary materials.