The most important reasons for fitting hearing aids is to permit access to speech information. One of the most important sounds for kids to hear is “s”. Why? Well, “s” provides critical grammatical information:
• pluralization (boot, boots),
• present vs past (she put it on, she puts it on)
• 3rd person present (she eats)
• Possessive pronouns, (hers, his, theirs)
• Contractions (it’s)
This grammatical information is very important for language learning and for literacy, and we, as audiologists, need to do whatever we can to get kids to hear it. So how do we know if a child can hear “s”.
Where is the energy for “s”?
The phoneme “s” has energy at 5000-6000. How are we going to be sure kids hear it? Don’t assume. When selecting hearing aids, we need to seek out aids that have extended high frequencies. After fitting the hearing aid, we again should not assume, but should test to be certain that the child is hearing high frequencies.
Testing to be sure the child hears “s”
Real ear testing will not tell us if a child is hearing high frequency sounds. It tells us what sound is reaching the tympanic membrane but not if it is reaching the auditory cortex. Threshold testing using noise band thresholds will provide information about what the child hears at each frequency band. We need to test 6000 and 8000 Hz to be sure that the child is hearing at sufficiently soft levels in the critical high frequencies. It is also essential that speech perception be tested. Standard speech perception tests will be more useful if we record phoneme errors, not just whether the word is correct. By looking at specific phoneme errors we can find out what phonemes present a problem for a child.
Many people use the Ling sounds (ah, ee, oo, sh, s and m) to see what a child is hearing and this can be especially useful for young children. This is a great screening test but needs to be carefully used. When audiologists use the Ling sounds it is important to remember that we should be presenting the sounds in the way they would present in general conversation. The phoneme “s” is not as loud as the other phonemes. In general conversation it can be 30 dB softer than the vowels. The audiologist needs to be careful not to peak all the phonemes on the VU meter since this would make all sounds equally loud and would indicate that the child is hearing what they are not actually hearing. We need to present sounds at a level at which the sound would fall in normal conversation. In other words, “s” will be softer. It testing for detection this can be difficult to control. If testing for discrimination, we can present with a carrier phrase (John, say /ah/; John say /s/) and let the phoneme fall where it may.
The Western Ontario Plurals Test
Once a child can repeat words point to pictures, the Western Ontario Plurals Test is a good way to assess high frequency perception. The test presents words in singular and plural format (boot, boots) and the testing provides information about whether the child can hear high frequencies.
What do we do if a child cannot hear high frequencies?
While it is true that many current hearing aids do not have bandwidth that extends to the high frequencies, we still need to test to demonstrate what the child hears and does not hear. The test information will be useful in planning remediation. First, we need to see if there is other technology that can provide high frequency information. It may require simply changing hearing aid settings, or trying different hearing aids. If that does not work, it may be time to consider cochlear implants. FM systems may provide more auditory access because of the close microphone, especially if it is an FM system that provides high frequency access. Auditory based therapy may also be useful in helping children improve auditory skills.
The important thing is to test to be sure that the child is hearing what she needs to hear and moving forward to fix it if she doesn’t.