Paul Dudley, 4th-generation Australian, retired audiologist
I was an audiologist for 41 years, and that question was asked a lot in the “early days”of hearing aid fitting. The level of sound reaching the eardrum via a hearing aid is typically 100 dBA or so. That is higher than what can be expected to cause damage to hearing in an industrial setting. This is a worry, especially in fitting hearing aids to children; we used to monitor the hearing of children fitted with hearing aids to check for any damage. You can program a hearing aid to compress the dynamic range of the signal delivered to the ear, or to limit the maximum output, but there has to be some compromise if the hearing aid is going to give useful benefit. If there is any effect on residual hearing, it is usually slight; I don't know why. There are exceptions. I remember one man, a WW1 veteran, who had convinced himself and others that he was profoundly deaf and had been fitted with a very powerful body-worn aid, which he wore for a year or so before he was discovered to have only a slight hearing loss. We had before-and-after records of his hearing which showed significant damage to the aided ear. Another memorable and extreme exception (from a memory going back to about 1972) was a girl about 8 years old, with a slight loss, considered a borderline candidate for hearing aid fitting. We discussed the pros and cons with the child's parents and teachers, but eventually fitted two low-power aids. Within a few weeks her hearing had deteriorated by 10 or 15 dB in both ears. I took one aid back and decreased the power in the other. A week or two later, the aided ear had shown a further slight deterioration, the unaided ear had recovered a little. When I saw her records a year or so later, she had a moderate loss in both ears, and she was wearing two hearing aids all the time. By this time, she really needed them. There may have been some other factor involved, but I blamed the hearing aids for the deterioration in her hearing. Prospective hearing-aid users often ask “Will they make my hearing worse?” I used to say probably not, because that is true. But what they may mean – and they may say it this way – is “Will I get dependent on them?” That's a trickier question. They will get to realize that the benefit from hearing aids is worth any initial annoyance, and they will want to wear them more. Then, wearing them more will trigger the thought that their hearing must have got worse. It probably hasn't. But I don't know why it hasn't.