Yesterday, Nolan had a hearing test at Buffalo Children's. His hearing has been hit-or-miss, and his speech has shown some regression. Nothing serious, mind you, but I still don't like the disappearance of our friends /s/, /j/, /ch/, and /z/,
I don't have his official audiogram in the mail right now, but his unaided test scores are fairly consistent with the October results. His left ear has dropped by about 20 dB at 2,000 Hz, in typical Nolan fashion.
For those who are unfamiliar with audiograms, Nolan cannot hear the sounds above the lines without his hearing aids. Basically, he can't hear any speech sounds at normal conversational volumes. If you shout at him or talk directly into his ear, he can hear enough to make out what you are saying. This is a moderately severe to severe hearing loss.
The reason for his "slushy" speech is more likely due to his aided hearing levels. Obtaining a pure-tone aided audiogram is a tricky business, because digital hearing aids suppress pure-tones as "background noise," which can make the audiogram a bit tricky to interpret. A child may show hearing thresholds of 30 dB across the board, for instance, but really be able to pick up voices at 20 dB.
With that said, Nolan's aided audiogram is terrible. The suppression effect should affect all frequencies equally, and Nolan's results are showing a significant drop-off in the high frequencies. His higher frequencies are not set appropriately for his hearing loss. His aided results are:
Hearing with both ears, Nolan can't really detect f, th, or s with his hearing aids. Z and V are also above the 35 dB line, which explains why he's having difficulty with those sounds. The audiologist noted he couldn't detect her voice until it was at 30 dB with his hearing aids on - essentially, Nolan has a mild-moderate hearing loss even with his hearing aids on.
I did ask about his bone conduction results and whether the BAHA could be an option for him (to eliminate some fluctuation and to give him better hearing). The audiologist stated that the sensorineural component of his hearing loss is too severe for a BAHA, so he is not a candidate for that technology.
His hearing loss isn't severe enough for a cochlear implant, so he doesn't qualify for that technology, either.
Since Buffalo Children's does not have a hearing aid program, they can't adjust Nolan's hearing aids. Since Nolan's current audiologist does not believe in aided testing, she won't adjust Nolan's hearing aids.
Buffalo Children's was very surprised that our current audiologist does not do real-ear measurements, as this may be part of the problem. The DSL program that sets hearing aid amplification levels is based on a set of averages, but is not specific to an individual child's ear canal size and hearing loss type. With a mixed loss, Nolan likely needs more amplification than a child with a purely sensorineural loss.
And then there is the problem of recruitment and a narrow dynamic range. Recruitment is a problem for people with severe losses. All of the outer hair cells are damaged, so only the inner hair cells remain to transmit sound in the cochlea. There is no gradual increase in the perception of volume - a sound goes from being inaudible to being WAY TOO LOUD very quickly. This makes setting hearing aids particularly difficult, as the level of amplification needed to make a sound audible is very close to the level which causes pain.
So the hearing aid program must be compressed to fit into this narrow range of hearing - the range between audibility and pain. We may not be able to increase his amplification by much, because it would cause him discomfort with sounds that are too loud.
Rock, meet hard place.
Other than the slushy speech sounds, however, Nolan is doing well - so we'll just repeat ourselves more often, use the FM more consistently, and monitor his hearing to see if (when) he qualifies for different hearing technology.