Abstract
Frequency lowering in hearing aids is not a new concept, but modern advances in technology
have allowed it to be performed more efficiently and on select portions of the spectrum.
Nonlinear frequency compression reduces the frequency spacing in a band of high-frequency
energy so that more information is carried in the audible bandwidth. Frequency transposition
and translation techniques lower only the part of the high-frequency spectrum that
likely contains important speech information. These advances may help overcome the
limited bandwidth in conventional hearing aids, which restrict access to high-frequency
information even for those with mild to moderate hearing loss. This is especially
important for young children learning speech and language. A framework is advanced
in which factors that influence individual differences in speech recognition can be
divided into extrinsic factors that affect the representation of the frequency-lowered
speech at the auditory periphery, including the specific technique and the settings
chosen for it, and intrinsic factors that contribute to an individual's ability to
learn and benefit from this signal. Finally, the importance of electroacoustically
verifying the output to avoid too little or too much lowering and the importance of
validating effectiveness of outcomes in individual users of the technology are emphasized.
Keywords
Hearing aids - frequency lowering - frequency compression - frequency transposition
