Quality ratings of frequency-compressed speech by participants with extensive high-frequency dead regions in the cochlea.
Marina Salorio-Corbetto, Thomas Baer, Brian C J Moore
PMID 27724057WHAT IT FOUND
Frequency-compressed speech was usually rated slightly worse than the reference hearing aid sound by five people with high-frequency dead regions.
Quality was worse when compression started below the dead region limit or used a ratio of 4.
Key findings
01Mean ratings were mostly between -1 and 0, where -1 meant a slight preference for the reference sound, so frequency compression usually caused small quality degradation.
02Group ratings were significantly lower when compression started at 0.75 f e than at 1.25 f e, and when the compression ratio was 4 than when it was 2 or 3.
03For P2 R and P7 L, audibility was very low for most conditions, which could account for ratings not varying much.
STILL TO COME
How it was doneWhat they found
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What it does not show
Only five participants (eight ears) were tested, so individual variability could not be separated from the effects of the settings. The study measured sound quality in a laboratory, not speech intelligibility or real-life hearing aid use. Speech intelligibility was not explored, so the results cannot show whether any quality change would help or hurt communication. Some ears had very low audibility, especially P2 R and P7 L, which may explain flat ratings rather than a true lack of effect. The TEN(HL) test was inconclusive or impossible at some frequencies because the maximum output level was reached. Participants with extensive dead regions are uncommon, with a prevalence of about 3%, so recruitment difficulty limits generalisability.
Declared interests
The supplied text does not give a named funder or conflict-of-interest declaration. The publication types note non-U.S. government research support. Phonak modified the hearing aids used to record the stimuli and provided software used for audibility calculations.
The easy way to misread this
Do not conclude that frequency compression improves speech understanding. The study tested only sound-quality ratings in five participants, and speech intelligibility was not measured.