This, of course, is the 64 million dollar question. The answer is “don’t assume.” There is only one way to know if hearing aids are doing well. Test them. Asking an adult with hearing loss if he is hearing okay with hearing aids is not necessarily going to give you the info you want because he may not have realistic expectations about what to compare them with. If it is better than without hearing aids, adults may be satisfied. But that does not mean the person is hearing as well as it is possible to hear with hearing aids.
For a child, asking is hopeless. Kids who have had hearing loss all their lives expect things to sound fuzzy. They do not know that other people hear clearly and do not need to struggle to understand. When I ask a kid if he is hearing well, I really cannot count on the answer. So I don’t ask. I ask if she is comfortable with the sound. Is it too loud? Is it annoying in some way? How does it compare to the other hearing aid or hearing aid settings? But not “Is it good enough?”
HOW ARE HEARING AIDS SET?
Many audiologists today fit hearing aids according to prescriptive formulas and leave it at that. That may not be the best thing to do. First, prescriptive formulas are an estimate, not necessarily perfect for the kid in front of you. Second, prescriptive formulas tell you what is reaching the tympanic membrane, not what is reaching the auditory brain.
We know that things interfere with sound being transmitted to the auditory brain and that is, in fact, what we need to know. So what should we be doing? I think we need to test to see how the child is hearing with the hearing aids. I know that obtaining aided thresholds has lost popularity lately, but I think this is a mistake. Real-ear testing tells you what is reaching the tympanic membrane. Aided thresholds tell you what is reaching the auditory brain – what the child is aware of hearing. Narrow-band noise, presented in short bursts from soft levels, will not turn on the noise circuit of the hearing aid and will let us know what the child is hearing throughout the frequency range.
Our goal would be to have the child hear at 10-15 dB throughout the frequency range. Table 1 shows test results for a child. It is clear from this that she is not hearing at sufficiently soft levels in the high frequencies. We know that with hearing like this she will have problems hearing high-frequency phonemes /(s/, /f/, /th/) , and miss grammatical markers like possessive and plurals. This will have significant negative results on language and literacy. So knowing that something is missing gives me the opportunity to correct the problem and provide her with more high-frequency information.
How exactly are we going to fix this? It may well mean that we are going to provide more sound than the prescriptive formula recommends. Let’s remember the key word here – “recommends.” It is definitely not written in stone. I care about only one thing: Can Trixie hear everything she needs to hear? I do not care what the prescriptive formula thinks should happen. It is only a starting point. I know I can adjust it to provide Trixie with what she needs to hear. And, in fact, that is what happened with the little girl in Table 1. By adding more gain in the high frequencies, I was able to end up with an aided audiogram at 15-20 dB across the frequency range and speech perception improved significantly when she had more high frequencies. Try it.
NEXT TOPIC – Assessing speech perception