whilst this article is to do with a new form of cochlear implant I think the figures and the problem of understanding speech in a noisy environment is well expounded.
"The National Institute on Deafness and Other Communication Disorders estimates that some 26 million American adults between the ages of 20 and 69 suffer from some loss of high-frequency hearing, which makes speech recognition especially difficult.
According to Roland, the loss of high-frequency hearing had left all study participants "in a difficult spot." Many were failing at work and in social environments because of their inability to hear and understand speech.
Roland says hearing aids were not an option for them because the sound-amplifying tools cannot sufficiently raise high-frequency sounds to improve understanding of speech, especially when there is any kind of background noise.
Roland also says the study participants had "too much residual hearing to lose," so having traditional cochlear implants -- one in each ear to replace both high- and low-frequency hearing -- was not an optimal option (although five study participants did eventually choose this route.)"
