"A soft hearing aid is one that is encased in a flexible shell."

Earmolds were originally designed only as a conduit through which the sound from a hearing aid could be delivered into the ear canal. At best, they did their job more or less effectively, at worst, they were (and, often, still are) simply a pain in the ear.

Some years ago, when behind-the-ear (BTE) hearing aids were the most popular models, it was discovered that the acoustical qualities of earmolds could be modified in ways very advantageous to users. For example, by increasing the diameter of the sound-tubing from the hearing aid receiver through the earmold (resulting in a 'horn" configuration), the sound output at the higher frequencies of a hearing aid could be increased by l0-15 dB compared to using a consistently narrower tubing throughout. Various size "vents" through an earmold could be used to decrease the low frequency response of a hearing aid as well as increase wearer comfort.

Initially, earmolds were made of hard material, such as acrylic, which would cause great discomfort if they didn't fit perfectly. But because with BTE hearing aids the earmold itself was physically separate from the aid, it was possible to fabricate softer earmolds while still obtaining the desired acoustical benefits. In addition to increasing wearer comfort, a bonus consideration was that the softer earmolds also helped reduce acoustic feedback.

This situation changed with the advent of in-the-ear (ITE) hearing aids of all kinds, ranging from the smallest ones that fit far down into the ear canal to ITE hearing aids that fill the entire "bowl" of the outer ear. Originally, the electronics of these ITE hearing aids were embedded in hard material, again possibly causing discomfort if the hearing aid casing (i.e., the "ear-mold" did not fit the ear perfectly. In such cases, the hearing aid dispenser would either have to buff the earmold, hoping to improve the fit, or recase the entire hearing aid, which would require new impressions to be made.

Additionally, with hard earmolds, even if the hearing aid seemed comfortable when the user's mouth was closed, acoustic squeal would often occur when the person was talking or chewing (this changes the shape of the external ear canal and permits sound to escape and be picked up by the microphone). Recently, in response to these potential problems, the earmold and hearing aid industry has developed "soft" hearing aids.

A soft hearing aid is one that is encased in a flexible shell. Instead of a hard-hollow cavity into which the electronic components are placed, a soft hearing aid employs a soft-hollow shell for the same purpose. For this type of aid, the part nearest the faceplate (the outer portion) is hard, but it becomes progressively softer toward its tip. At least two companies (Telex and Sound Parts) make all styles of hearing aids, for every degree of hearing loss, using soft hollow shells. At least one hearing aid company, General Hearing Instruments, has developed hearing aids in which the electronics are enveloped completely within the soft material, thus eliminating most internal air spaces.

All "soft" hearing aids are supposed to be more comfortable, to conform more closely with the ear canal as it changes shape during speech or chewing and to reduce feedback, compared to traditional acrylic casings. All these are commendable goals. Too soft, however, and there may be user problems. As one writer (Dr Robert Turner in the September 2000 issue of The Hearing Journal) rather inelegantly and humorously put it: "it's easier to stick a carrot in one's ear than a noodle." He was basically cautioning us to expect somewhat more difficulty inserting these soft hearing aids in the ear because of increased friction between the earmold and the ear canal.

Dr. Turner also pointed out that as of yet, there are no independent research studies that have evaluated these products to determine real-life satisfaction or to quantify the actual benefits perceived. Still, I think we can fairly accept the notion that the softer the material we stick in our ear canals, the more comfortable we're likely to feel (in other words, as long as it can be inserted, most of us would undoubtedly prefer a wet noodle to a hard carrot in our ears!). In short, it does appear that in the future more and more hearing aids will be made using "soft" technology.

From Hearing Loss, March/April, 2001. This column is supported, in part, by GRANT #133E980010 from the U.S. Department of Education, NIDRR, to the Lexington Center.