Justification for Specific Hearing Aid Technology - A WSD Workshop

Scot Frink presented this workshop at the Western Symposium on Deafness (WSD) Conference in April 2005 in San Diego. Scot provided a good overview of hearing aid technology and how a consumer should go about choosing an appropriate hearing aid.

Yes, I know some of you will have comments about the contents of this article ;-) . So please do send them to larry@hearinglossweb.com .

Here's what Scott had to say.

Hearing Aid Technology

Scot began his presentation with a review of the best hearing technology over the last 100 years. His list included:
1902 - ear horn
1930 - body aid
1955 - behind-the-ear (BTE) hearing aid
1975 - in-the-ear (ITE) hearing aid
1980 - compression technology
1988 - programmable technology
1996 - digital technology
2000 - second generation digital technology
2004 - third generation digital technology

Scot then presented his thoughts on what technology can do. He included miniaturization, improved sound quality, the control of loud sounds, and better understanding in specialized listening situations, including background noise, on the telephone, in the car, and hunting (where a person with normal hearing wants to protect his ears from the noise of shooting, but still be able to hear animals rustling in the bushes).

He also listed some things that technology can NOT do, including restoring 100% of lost hearing, giving perfect intelligibility for soft speakers, eliminating background noise, eliminating the need for batteries, eliminating the need for repairs, and preventing moisture and earwax from damaging hearing aids.

There are a variety of types of hearing aids available, and each person should select an instrument that best suits her needs. Some helpful things to keep in mind are that a digital hearing aid is not necessarily better than an analog aid, a digital aid does not have to be expensive, and that instrument cost and degree of hearing loss are important factors in choosing an aid, but should not be the only factors.

One of the most common complaints people have about hearing aids is their expense. There's no question that top of the line hearing aids are expensive, but that's always true of the newest technology. The cost of hearing aids employing older technology has actually decreased over the years. For example, in 1996 a top of the line two-channel digital aid cost $2500. The equivalent aid today (except that it has six channels instead of only two) is $995. The bottom end has remained pretty flat. A basic linear instrument that cost $495 in 1990 still costs $495 today. While the price is constant in current dollars, today's instrument is considerably less expensive if prices are adjusted for inflation.

Analog hearing aids will soon be phased out, as the market goes 100% digital. Factors driving this trend include an easier assembly process, reduced chip costs, and more easily addressed patient issues.

But note that one pair of digital hearing aids will cost $1600, while another pair will cost $6000. So what's the difference? Among the most important differences are the number of channels, differences in noise reduction technology, different style choices, integration with wireless technologies (e.g. FM and Bluetooth), and automation of features.

Selecting an Appropriate Aid

Several factors must be considered in selecting appropriate aids for a particular individual. These include:
- Degree of hearing loss
- Hearing loss configuration
- Progressive nature of hearing loss
- Tolerance issues
- Background noise issues
- Specific needs of the individual

One of the first factors to be considered is the degree of hearing loss. Greater hearing loss requires more powerful hearing aids. But modern technology facilitates the construction of hearing aids that will benefit virtually everyone with hearing loss. People with severe or profound losses may find digital feedback managers particularly beneficial, because they allow the hearing aid to provide increased power without producing feedback. In general, more severe hearing losses require more power, which means larger aids.

A second important factor in selecting a hearing aid is the configuration of the hearing loss. A flat hearing loss (one with the same loss at all frequencies) is the easiest to treat, requiring only a basic amplifier. Such a hearing loss does NOT call for advanced technologies, although other factors may.

Almost as easy to treat is the very common audiogram in which hearing loss increases with frequency (high frequency hearing loss). This type of loss is also well-treated with basic technology.

Complex and oddly-shaped audiograms generally require more advanced technology. Such audiograms require different amounts of amplification at different frequencies, so multi-channel instruments are appropriate choices. In general the more complex the audiogram, the more channels are required to adequately correct the hearing loss. These more problematic losses include steeply-sloped losses, reverse slope losses, "cookie bite" losses, and "reverse cookie bite" losses.

A third consideration in the selection of a hearing aid is the progressive nature of the hearing loss. If a person's hearing loss is progressive, she should select an aid that provides enough adjustment to ensure that the aid will meet her needs for several years. While conventional (analog) aids offer minimal adjustments, programmable aids offer more, and digital aids even more. Some digital aids have upgradeable circuits, which allow software upgrades to extend the life of the aid even further.

The first hearing aid with upgradeable circuits was introduced in 2000. The initial circuitry included five channels, and did not include the capability to adjust the noise reduction characteristics. A software upgrade increased the number of channels to 20 and also provided for adjustable noise reduction characteristics. During that same time, the cost of that hearing aid fell from $2500 to $1900.

Note that choosing an aid that facilitates adjustments doesn't mean you'll be able to use it forever. Wear and tear will eventually require its replacement; smaller aids generally wear out sooner. The life expectancy of a completely-in-the-canal (CIC) aid is about three years, while a behind-the-ear (BTE) hearing aid should last five to seven years.

Part Two