Degree and Configuration of Hearing Loss, Dead Regions, and Speech Understanding
Recently, Cox et al (2011) reported that subjects who tested positive for cochlear dead regions generally performed better when more high-frequency cues were available, while listeners without dead regions acquired even greater benefit from high-frequency cues. In essence, they did not support the concept of limiting or reducing high-frequency gain for subjects who tested positive for dead regions (see Beck, 2011). More recently, Hornsby, Johnson, and Picou (2011) evaluated 62 adults with various degrees of high- and low-frequency hearing loss to examine "the contribution of speech information in different frequency regions…." In accordance with previous research, they noted benefit from speech information in a particular frequency region decreases as degree of hearing loss increases.
Nonetheless, Hornsby, Johnson, and Picou reported that the "degree of hearing loss" was a more formidable factor with regard to performance differences than was audibility, and configuration of hearing loss is also important. Indeed, except for individuals with very steeply sloping high frequency hearing loss, high-frequency amplification (to approximately 9000 Hz) provided a beneficial effect or did not "significantly degrade" speech understanding.
The authors note that "across a wide range and configuration of hearing losses, access to high frequency information speech information (3,534 to 8,976 Hz) is needed to achieve optimal intelligibility." That is, when attempting to maximize speech intelligibility for people with a wide range of high frequency hearing losses, extended high frequency hearing amplification is generally beneficial.
For More Information, References, and Recommendations
Beck DL, Olsen J. (2008): Extended Bandwidth in Hearing Aids. Hearing Review October.
Cox RM, Alexander GC, Johnson J, Rivera I. (2011) Cochlear dead Regions in Typical Hearing Aid Candidates: Prevalence and Implications for Use of High-Frequency Speech Cues. Ear & Hearing 32(3):339-348.
Hornsby BWY, Johnson EE, Picou E. (2011) Effects of Degree and Configuration of Hearing Loss on the Contribution of High-and-Low Frequency Speech Information to Bilateral Speech Understanding. Ear & Hearing 32(5):543-555.