SPEECH PERCEPTION – THE BASICS
The real goal of technology is to assure that kids are hearing and understanding speech. First we need to know if the hearing aids are set appropriately (see HOW DO I KNOW IF THE HEARING AIDS ARE WORKING WELL?) Next we need to look at how well the child understands speech. This is a big topic so we will need to divide it up. In this blog I am going to start talking about the basics, then we can talk about specifics for different age groups in future blogs.
During basic hearing tests we test speech perception at comfortably loud levels with earphones. For example, if a child has a 50 dB hearing loss, we will test speech perception at 90 dB. This is a good way to test with earphones; it gives a good estimate of what we can expect under good listening conditions. However, when we test kids with hearing aids or cochlear implants we want to know how the child is hearing in real life situations. Testing at loud levels may tell us how a child hears in the best conditions but not how they hear in critical daily listening situations. Kids with typical hearing hear well when listening to loud, normal and soft speech. They learn a lot by “overhearing” things around them – hearing soft speech – sometimes hearing things we wish they did not hear. We want our kids with hearing loss to be able to do the same. It is important that kids hear normal conversation (50 dBHL) and soft conversation (35 dBHL). They need to hear and understand when it is quiet and when there is background noise because, unfortunately, the world is noisy. If a child hears well at normal conversation but poorly for soft speech and in noise it means that she will have trouble hearing in many daily situations. She will have problems hearing with the talker is more than 4-5 feet away, in the kitchen when the dishwasher is running, in the playground, in school. This will result in delays in both language and literacy.
The table below shows an example of test results for one child. This child hears well at normal conversation but poorly for soft speech and in noise. If this child was only tested at normal conversational levels we would not know that he was having problems and would not know that we needed to make a repair.
|50dB HL +5 SNR||54%|
Looking at these test results, we know that language exposure will be limited. We know that we need to find a way to improve speech perception for soft speech and speech in noise. What is the effect of this poor speech perception? It will definitely interfere with learning. The child will have less exposure to speech, which means that it will take longer for him to get the language exposure that a typical child has. If we want him to compete with his peers we need to fix this.
The first thing to try is to change hearing aid settings. It may simple require making the hearing aids louder. If after changing settings and retesting, if things are not better it may be necessary to try different hearing aids, or to consider moving to a cochlear implant. It may be time to consider using an FM system on a full time basis to provide access to distant speech and to speech in noise. If we know that the technology is providing enough gain (the child is hearing at sufficiently soft levels throughout the frequency range) but speech perception is not good enough, we should look at the therapy the child is receiving. For a child to learn to use audition it is essential that he have listening and spoken language therapy designed specifically to develop auditory skills.
In summary, never give up. We CAN and MUST provide kids with good auditory access to speech and language. We need to be sure kids are hearing what they need to hear. If not, we need to fix it.