Low Frequency Hearing Loss Fitting Techniques

I figured I would post an article link which I find is very helpful in providing direction on fitting hearing aids for reverse slope hearing losses. While my reverse slope loss is only moderate, it is an uncommon loss thus getting fitted for hearing aids took a lot of trial and error and research on my part. Reverse slope losses are estimated to occur in 1/12,000 HOH people.

Because of the lack of hands-on practice with fitting these types of losses, many audis will fit the loss with what makes the most sense theoretically. Ex. amplifying the loss according to the audiogram which means boosting your low frequencies where the loss generally exists. They will also suggest a closed dome or mold to seal in the low frequencies. However, this is completely the wrong approach to fitting hearing aids for reverse slope losses

The below article written by Donald J. Schum, PhD (VP of Audiology at Oticon) provides very clear and concise fitting approaches for low frequency losses.
Standard Versus Special Fitting Approaches71

Here’s an excerpt from the article:

[I]A hearing loss correction approach for patients with low frequency hearing loss would call for significant amount of gain in the low frequencies and little or no gain in the higher frequencies. This approach enhances audibility in a region where there is minimal amount of speech information, and also greatly increases the risk of upper spread of masking. Further, these patients were historically fit with powerful low-pass hearing aids and closed ear molds in order to maintain the frequency response in the low frequencies. Before the widespread use a real-ear techniques for verification, patients fit in this manner would often end up with an insertion loss in the high frequencies.

Schum and Collins (1992) reported on a group of patients with low frequency SNHL who were fit with a variety of different amplification schemes. They found that the traditional approach of mirroring the audiogram did not work nearly as effectively as approaches that reduced gain in the lower frequencies and maintained at least a minimum amount of insertion gain in the higher frequencies. Again, when viewed from a residual capabilities standpoint, these patients are looking for amplification characteristics that allow them to hear the most important parts of the speech signal using regions of their hearing that seem to have the most residual capacity.

Using a residual capabilities approach, a minimum of 10 to 15 dB insertion gain at 2000 Hz and above would be recommended for these patients, even if hearing is normal. Insertion gain in the low and middle frequencies should be set at no more than 15 to 20 dB.