Background: Previous research has indicated that children with moderate hearing loss experience
difficulty with recognition of high-frequency speech sounds, such as fricatives and
affricates. Conventional behind-the-ear (BTE) amplification typically does not provide
ample output in the high frequencies (4000 Hz and beyond) to ensure optimal audibility
for these sounds.
Purpose: To evaluate nonlinear frequency compression (NLFC) as a means to improve speech recognition
for children with moderate to moderately severe hearing loss.
Research Design: Within subject, crossover design with repeated measures across test conditions.
Study Sample: Fifteen children, aged 5–13 yr, with moderate to moderately severe high-frequency
sensorineural hearing loss were fitted with Phonak Nios, microsized, BTE hearing aids.
These children were previous users of digital hearing aids and communicated via spoken
language. Their speech and language abilities were age-appropriate.
Data Collection and Analysis: Aided thresholds and speech recognition in quiet and in noise were assessed after
6 wk of use with NLFC and 6 wk of use without NLFC. Participants were randomly assigned
to counter-balanced groups so that eight participants began the first 6 wk trial with
NLFC enabled and the other seven participants started with NLFC disabled. Then, the
provision of NLFC was switched for the second 6 wk trial. Speech recognition in quiet
was assessed via word recognition assessments with the University of Western Ontario
(UWO) Plural Test and recognition of vowel-consonant-vowel nonsense syllables with
the Phonak Logatome test. Speech recognition in noise was assessed by evaluating the
signal-to-noise ratio in dB for 50% correct performance on the Bamford-Kowal-Bench
Speech-in-Noise (BKB-SIN) test, an adaptive test of speech perception in a multitalker
babble background.
Results: Aided thresholds for high-frequency stimuli were significantly better when NLFC was
enabled, and use of NLFC resulted in significantly better speech recognition in quiet
for the UWO Plural Test and for the phonemes /d/ and /s/ on the Phonak Logatome test.
There was not a statistically significant difference in performance on the BKB-SIN
test between the NLFC enabled and disabled conditions.
Conclusions: These results indicate that NLFC improves audibility for and recognition of high-frequency
speech sounds for children with moderate to moderately severe hearing loss in quiet
listening situations.
Key Words
Hearing aids - moderate hearing loss - nonlinear frequency compression
