Discrimination of Gain Increments in Speech-Shaped Noises.
Benjamin Caswell-Midwinter, William M Whitmer
PMID 30803400WHAT IT FOUND
The smallest noticeable gain increments in 38 hearing-aid candidates or users were 2.8 dB across most frequency bands, 4.5 dB at 0.25 kHz, and 1.5 dB across all bands.
Smaller changes may not be noticed.
Key findings
01The median frequency-band threshold was 2.8 dB for the 0.5 to 4 kHz octave bands and the 6 kHz high-pass band, and 4.5 dB for the 0.25 kHz low-pass band.
02The median broadband threshold was 1.5 dB, and frequency-band thresholds were significantly greater than broadband thresholds.
03For noisier conditions, the paper suggests frequency-band gain adjustments of 6 dB below 1 kHz and 5 dB at or above 1 kHz may be noticeable.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
Read the rest of this summary
You get three full summaries a month, free, and we do not ask for a card. Search, the TL;DRs and your library stay unlimited either way.
What it does not show
The thresholds were measured in quiet speech-shaped noises, not in speech or noisy everyday environments. The sounds were processed linearly, while most modern hearing aids use compression, which may make increment discrimination harder. Only gain increments were tested. Decrement thresholds were difficult to measure in a pilot study, and 21% were excluded. About 9% of threshold estimates were excluded because of poor fits at the main analysis, and about 5% were excluded at the stricter analysis. Five participants did not complete the cognitive tasks, so cognitive correlations were based on 33 participants. The sample was 38 participants, and thresholds varied across participants. The 6 kHz threshold correlation was sensitive to a few severe cases; removing one elevated value eliminated the significant correlation. The paper notes that meeting gain targets does not guarantee objective benefit or patient satisfaction.
Declared interests
Funding was provided by the Chief Scientist Office and the Medical Research Council. The metadata lists research support from non-U.S. government sources.
The easy way to misread this
Do not assume that a small hearing-aid gain change will be noticed by a patient. These thresholds were measured in quiet speech-shaped noises, not in speech or noisy everyday environments, and they do not show that an adjustment improves patient benefit.