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Choices in Hearing Aids

Many years of interacting with a variety of hard of hearing people has taught me that most hard of hearing people feel they were not informed about important available options before selecting a hearing aid. This paper is an attempt to disseminate such information.
 

The following is a very brief summary of some considerations in choosing a hearing aid. It covers basic hearing aid options and some advanced technologies. This paper does not claim to cover all available technologies; for example, it does not discuss digital hearing aids.

Dana Mulvany, MSW, LCSW
dmulvany@usa.net
http://members.tripod.com/~Dana_Mulvany
 
 

Basic Hearing Aid Options



I recommend that every hard of hearing person have telecoils in their hearing aids if at all possible. If a person anticipates needing to use a telephone around computer equipment or heavy machinery, the person should consider direct audio input (DAI) capability as an important additional criteria in hearing aid selection. (With DAI, it is possible to use an assistive device which would avoid the electromagnetic interference to which many telecoils are vulnerable.)

Consumers often do not realize that there is considerable variation in the quality of the telecoil among hearing aids and they may unknowingly settle for a hearing aid which does not assist them adequately with the telephone. If the consumer hears fairly well with a hearing aid (without lipreading) but does not hear well on an amplified telephone with the hearing aid's telecoil, I would suggest exploring whether another hearing aid suitable for the hearing loss might have a better-designed telecoil.

Telecoils (AKA T-coils, T-switches)

Telecoils are a frequently available mechanism inside the hearing aid which enable the hearing aid to be used directly with hearing-aid compatible telephones and most assistive listening devices. Telecoils are activated by turning the switch to the T-position on the hearing aid(s). Telecoils pick up the electromagnetic field generated by hearing-aid compatible telephones, audio loop systems, and powered neckloops and silhouettes; the signal is then converted to sound by the hearing aid. (Neckloops and silhouettes are "couplers" which couple a device like an FM or infrared receiver to the hearing aid.)

PRO:  Using telecoils avoids the feedback that often results from putting a hearing aid up against a telephone, can help prevent exposure to overamplification (many hearing aids prevent sound from getting too loud for the individual) and eliminates background noise, providing much better access to the telephone.

CON:  Telecoils can pick up electromagnetic interference from certain computer monitors, heavy machinery, airplanes and digital mobile phones. Telecoils usually need additional amplification, and the sound through telecoils may sound different than through the normal mode of the hearing aid. They are often ineffectively positioned in canal and in-the-ear hearing aids due to the lack of room inside the hearing aid for optimal placement.  First-time hearing aid users, elderly people, and other people with cognitive disabilities may get confused and leave their hearing aid on the telecoil setting, which shuts out the environmental sound and may cause them and others to think there is something wrong with the hearing aid (this could be addressed through better training in many cases).

Direct Audio Input

Direct Audio Input (DAI) is a direct-connect method of utilizing the hearing aids with other devices. What is heard through DAI may sound better for some people than what they hear through the telecoil, but DAI requires a physical connection via a proprietary boot or "shoe" and usually a wire. Due to the direct connection, it avoids the electromagnetic interference(EMI) to which telecoils can be susceptible and is an important option for people who need to use the telephone around sources of EMI such as some computer monitors or heavy machinery. DAI  capability is usually available only in selected behind-the-ear hearing aids. Wires connecting the hearing aid to a device need to be well-shielded as they can unintentionally act as antennas for nearby radio transmitters.

Many owners of BTE hearing aids don't realize that the hearing aid has DAI capability.  Look at your hearing aid to see if there are metal contact points on the hearing aid.  (This may be covered up on some hearing aids.)

Remote Controls

Remote controls are available with some hearing aids. They are particularly useful for people with manual dexterity problems and/or visual impairments who would have trouble managing small switches directly on the hearing aid. Consider whether it is possible to wear the remote control around the neck or securely attached to a belt as this would minimize the risk of loss and damage. A remote control is sometimes required to activate certain programs set inside the hearing aid.
 


Advanced Hearing Aid Technology



A major problem for hard of hearing people is the difficulty of hearing in noise.  A simple hearing aid can amplify all the noise, not simply speech sounds, and the result is that the noise can drown out the speech that the hard of hearing person wants to understand.  Compared to people with normal hearing, hard of hearing people need an increased "signal-to-noise" ratio (the desired speech "signal" needs to be louder than the surrounding "noise" in order for the hard of hearing person to understand speech).   There are several strategies used within hearing aids which have been shown to be effective in improving the "signal-to-noise" ratio: hearing aids with a single microphone which is directional, multi-microphone technology within the hearing aid itself, and hearing aids with boots to receive FM transmission.*  (It is also possible to use assistive listening devices to improve comprehension of speech in noise.)

*Some programmable hearing aids have the ability to activate a "noise" programs which act by suppressing certain frequencies.  These may be particularly helpful in situations where there is mechanical noise, but in parties or restaurants where much of the noise is at the speech frequencies, there may be less benefit experienced.    The best way to hear in noise is to bring one's "receiver" as close as possible to the source of the desired sound---the receiver can be the ear itself, the hearing aid, or the microphone of an assistive listening system (such as the microphone for an FM system, a hand-held amplifier, or a DAI microphone).

Explanation of Multi-Microphone Technology (MMT)

Phonak's AudioZoom
http://www.phonak.com
The AudioZoom technology uses two microphones to provide a better signal-to-noise ratio when noise is at the back of the user. (The microphone in the back seems to be used in a way to "subtract" the noise from the back.)  Phonak cites two studies in 1998 as showing that the AudioZoom was superior to digital hearing aids in understanding speech in noise.  Links to the studies are available via http://www.phonak.com/stop/1142.html.  The user has the option of switching between omnidirectional and directional mode.

Some other hearing aids may also use multi-microphone technology; please let me know if you learn about other brands of hearing aids which use MMT.
 

Hearing Aids with Wireless FM Reception Capabilities

Phonak's Microlink
Phonak manufactures a special FM boot for its hearing aids with direct audio input capability which is used with a separate HandyMic (a transmitter and microphone).
http://www.phonak.com

AVR Sonovation's Extend-Ear series (BTE/FM system)
(Uses wide-band technology and boot to change frequencies)
http://www.avrsono.com

Telex BTE-FM hearing aids
http://www.telex.com/hearing/WALS/WALS_select.htm

Wireless FM Coupling Systems

Phonic Ear Telepin's system uses an FM boot and  neckloop for certain DAI-capable hearing aids; this minimizes the type of electromagnetic interference to which telecoils are vulnerable.  More information available at  http://www.phonicear.com/telepind.html.
 

Transposition of High Frequencies
AVR's ImpaCt
Useful for people whose hearing loss is severe or profound at high frequencies but who have some hearing at the lower frequencies.  High frequency sounds can be compressed to a lower frequency within the person's hearing range (transposing them).
http://www.avrsono.com/
 
 
 

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Updated June 7, 1999