A high frequency hearing loss that is most often caused by noise exposure has traditionally been one of the most difficult to fit with hearing aids.
This is because by definition a high frequency hearing loss is one in which the patient has normal or near normal hearing in the low frequencies and out to about 1000Hz. The hearing then falls dramatically like a “ski slope” in the higher frequencies.
An article I read describes the difficulties of this situation well. It was written by Josef Chalupper and Robert Kasanmascheff for Audiology Online on September 15th, 2008. Although not a recent article, the findings are relevant today. It states that the patient’s normal hearing in the low frequencies increases the occlusion effect (A person’s own voice sounds like he or she is in a barrel.) to the point of being annoying. This can be reduced by an open canal fitting. A thin tube BTE (behind the ear) or RIC (receiver in the canal) hearing aid is ideal for this because the receiver can almost float in the ear canal.
The thin tube BTE or the RIC also have superior directionality to the ITE (in the ear) custom hearing aid because of the dual microphones placement and their distance apart. The placement of the hearing aid behind the ear allows for one microphone to be facing forward (or close to it) and one microphone to be facing to the rear of the patient. Therefore, the technology permits the hearing aid to adjust to the desired sound appropriately.
The design of the thin tube BTE or RIC allows the hearing aid microphone and the receiver to be further apart than in the ITE style. Therefore, by design, this style aid is less likely to whistle (or feedback) when the high frequencies are amplified. These are precisely the frequencies this type of patient needs in order to understand speech more clearly because the high frequencies are where many of the sibilant consonants are found. Unlike in 2008, today’s thin tube BTE and RIC hearing aids are also less likely to whistle due to feedback cancelation technology that senses the frequencies that would likely cause a problem and take them “out of phase” thereby eliminating the problem. Therefore, more patients with high frequency hearing loss are enjoying the benefits of hearing aids, today, because of thin tube BTE and RIC hearing aids than ever before.