Purpose: To investigate the effects of vocabulary, working memory, age, semantic
context, and signal-to-noise-ratio (SNR) on speech recognition in adverse conditions
(multitalker babble) in normal-hearing listeners aged 18-35. First, a general
hypothesis was tested that listeners with larger receptive vocabularies would be
more accurate at recognising speech in noise than listeners with more limited
receptive vocabularies, even when target stimuli are words with high lexical
frequency. A second more specific hypothesis was that the vocabulary would be
predictive of speech recognition accuracy when the signal was moderately
degraded, but not mildly or severely degraded.
Method: 80 sentences with a high (HP) or low (LP) degree of semantic predictability
(40 HP and 40 LP) were recorded from a male speaker of NZ English. These
sentences were used as experimental target stimuli, and presented in multitalker
babble at four SNRs: -8, -4, 0 and 4 dB SNR. Thirty-five participants (11 males and
24 females, aged 18 to 35), with puretone hearing thresholds of 15 dB HL or better,
completed the Peabody Picture Vocabulary Test (PPVT) and the Wechsler Adult
Intelligence Scale (WAIS) vocabulary subtest, the WAIS working memory subtests,
and the experimental listening task in which they were required to repeat back the
target sentences.
Results: There was considerable variability between listeners in speech recognition
performance, in terms of percent words accurately recognised overall (M = 45.8%;
SD = 7.4) and for both HP (M = 54.4%; SD = 9.8) and LP (M = 35%; SD = 8.9)
conditions. Hierarchical multiple regression analyses revealed that receptive (PPVT)
and productive (WAIS) vocabulary knowledge, but not working memory, contributed 8
significant variance to listeners’ speech recognition scores overall and in both the HP
and LP conditions. Further regression analyses at individual SNR levels showed that
receptive vocabulary contributed significant variance to listening recognition scores
in all predictability and SNR conditions except the most favourable (HP stimuli at 4
dB SNR) and least favourable (LP stimuli at -8 dB SNR) listening conditions.
Working memory and age were not significantly related to overall listening score, HP
listening score, or LP listening score, but age did contribute significant variance in
the - 4dB SNR LP condition.
Conclusion: The results provide further evidence that greater vocabulary knowledge
is associated with improved speech recognition in adverse conditions. This effect
was salient in mid-range adverse listening conditions, but was not apparent in highly
favourable and extremely poor listening conditions. The results were interpreted to
suggest that in moderately adverse listening conditions listeners with larger lexicons
may be better able to exploit redundancies and/or intelligible ‘glimpses’ in the speech
signal.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/9334 |
| Date | January 2014 |
| Creators | Dalrymple-Alford, Joseph |
| Publisher | University of Canterbury. Communication Disorders |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Joseph Dalrymple-Alford, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
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