Influence of Loudness Compression on Hearing with Bone Anchored Hearing Implants

Bone Anchored Hearing Implants (BAHI) are 
routinely used in patients with conductive or mixed hearing loss, e.g. 
if conventional air conduction hearing aids cannot be used. New 
sound processors and new fitting software now allow the adjustment 
of parameters such as loudness compression ratios or maximum 
power output separately. Today it is unclear, how the choice of these 
parameters influences aided speech understanding in BAHI users. 
In this prospective experimental study, the effect of varying the 
compression ratio and lowering the maximum power output in a 
BAHI were investigated. 
Twelve experienced adult subjects with a mixed hearing loss 
participated in this study. Four different compression ratios (1.0; 1.3; 
1.6; 2.0) were tested along with two different maximum power output 
settings, resulting in a total of eight different programs. Each 
participant tested each program during two weeks. A blinded Latin 
square design was used to minimize bias. 
For each of the eight programs, speech understanding in quiet and 
in noise was assessed. For speech in quiet, the Freiburg number test 
and the Freiburg monosyllabic word test at 50, 65, and 80 dB SPL 
were used. For speech in noise, the Oldenburg sentence test was 
administered. 
Speech understanding in quiet and in noise was improved 
significantly in the aided condition in any program, when compared 
to the unaided condition. However, no significant differences were 
found between any of the eight programs. In contrast, on a subjective 
level there was a significant preference for medium compression 
ratios of 1.3 to 1.6 and higher maximum power output.

• Anja Kurz
• Marc Flynn
• Tobias Good
• Marco Caversaccio
• Martin Kompis

• Bone Anchored Hearing Implant
• Compression
• Maximum Power Output
• Speech understanding.

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