Hearing Aids

Timothy C. Hain, MD

Last modified: 10/2012

What Treatments are Available?

For many hearing disorders, there is no actual available cure. However, there are assistive devices and some promising new treatments that allow patients to manage their hearing disorders. While regeneration of inner ear hair cells is presently not possible, as medicine advances, it seems very likely that a method will be found to regrow inner ear hair cells in the future.

Hearing Aids

Hearing aids are electrical devices that assist in optimizing perception of speech or other sounds. Most hearing aids are designed for hearing impaired individuals, of which there are approximately 37 million in the United States (Schiller et al 2012).

A basic hearing aid consists of a microphone, amplifier, volume control, battery and receiver. A straightforward approach is simply to amplify sound coming in. This approach often fails due to a limited range of usable volumes (it might be either too loud or too soft). More recent designs use compression circuitry to represent the full range of sounds within the range tolerated by the wearer. Digital hearing aids and programmable hearing aids offer more flexibility in the processing. It is often desirable to have a hearing aid behave differently in a busy room than when speaking one-on-one. This is possible with a programmable aid.

Who Needs a Hearing Aid?

In essence, you need a hearing aid if you have hearing problems and the cost/benefit ratio of a particular aid is reasonable. An “ideal” hearing aid candidate is someone with a mild or moderate bilateral hearing loss, who has experienced a noticeable communication handicap. Many individuals who have good hearing on one side can adjust reasonably well to any degree of hearing loss on the other side, and for this reason, most people that get hearing aids have bilateral decreases in hearing.

Hearing aids are not indicated for an ear with minor hearing loss, and are also not very useful in an ear with profound hearing loss. In other words, hearing aids are usually most appreciated in people with mild to moderate hearing loss on both sides. Sometimes an “assistive device” can be used — this is a small personal amplifier. Amplifiers are also available for telephones and TVs. The telephone company may supply you with one for your telephone at little or no charge. You should be able to find many vendors by using “Google” to search for “assistive devices for hearing”. Some low-end assistive devices sell for as little as $50.

Be sure that you need a hearing aid. It is estimated that two-thirds of all hearing aids go unworn (or into the drawer).

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What Tests are Necessary Before Selecting a Hearing Aid?

An audiometric evaluation should be performed to determine the type of hearing loss (sensorineural, conductive or central), the degree, and the frequency slope. The evaluation should also be able to predict the amount of benefit that an aid will provide, in terms of speech comprehension.

In selecting a hearing aid, a special appointment called a “fitting” is usually needed. The fitting maps out how much amplification is needed, the uncomfortable loudness level, (ULC) (which is the maximum tolerable loudness) and the most comfortable listening level (MCL). The dynamic range is defined as ULC minus MCL. Fitting also involves selection of the style of hearing aid, and usually selection or fabrication of an ear-mold. Recently, the process has gotten a little easier as off-the-shelf aids (for example, the Songbird) seem to provide as good results as the more arduous process. Social service agencies are often involved with hearing aid dispensing.

An otologic evaluation should also be performed to determine whether medical or surgical treatment is possible (for example, ear wax removal). Medical clearance is advisable before purchasing a hearing aid.

Types of Hearing Aids

There are many types of hearing aids available in the market. Selecting a hearing aid depends on the specific hearing loss, the cosmetic appearance, and the amount one wishes to spend. Hearing aids can be categorized by technology and by style (size and appearance). The different technologies are available in the different styles.

Technologies

  1. Analog (now nearly obsolete). There are several circuits.
  2. Simple programmable. (now nearly obsolete).
  3. Complex programmable.
  4. 4. Digital. Flexible but expensive. Most commonly prescribed.
  5. Implantable aids. Somewhat better performance can be obtained by implanting the hearing aid.

New advances that may be beneficial include intra-aural silicone directional microphones that allow the wearer to better understand sounds from multiple directions (Bentler 2005, Miles & Hoy 2006, Miles et al 2009, Ricketts 2005)and bone anchored hearing aids (BAHA). BAHA percutaneously transmit sound through the skull and may be more effective than traditional aids in some patients with conductive hearing loss (Hol et al 2005) and single-sided deafness (Christensen et al 2010, Linstrom et al 2009). Interest is growing for bilateral BAHA implantation for bilateral conductive hearing losses, although the efficacy of two devices is still in question (Janssen et al 2012). An implantable ossicular stimulator has proven effective in clinical trials (Jenkins et al 2007, Jenkins et al 2004).

Styles of Hearing Aids

  1. Assistive listening devices. A large variety of devices are available at much lower cost than hearing aids. Some of these are free. Telephone companies provide free amplifiers and ringers if patients present a physician or audiologist release. Hotels provide telephone amplifiers in 10 percent of rooms. Examples are devices that flash lights when the telephone rings, vibration devices when the doorbell sounds, flashing smoke alarms, television amplifiers, etc.
  2. Behind the ear (BTE). Cheapest, easiest to adjust, less feedback than other devices. Fairly visible. Most powerful. Fewest number of problems with wax or infections.
  3. In the ear (ITE). Low visibility; harder to put in and adjust.
  4. In the canal (ITC). Very low visibility. Clearer than Assistive listening devices and BTE. Lower power. Patients with tremor or poor eyesight are not good candidates.
  5. Completely in the canal (CIC). Cannot be seen. Requires tight fit. Hard to adjust and remove. Clearer than assistive listening devices and BTE. Patients with tremor or poor eyesight are not good candidates.

In addition to technology and style, one must decide between wearing a hearing aid in one ear (monaural) or wearing a hearing aid in both ears ( binaural). Binaural amplification is generally better than monaural because it minimizes the impact of “head shadow” drop off, improves sound localization, and widens the dynamic range. However, having two hearing aids costs twice as much, and it is more trouble to keep two hearing aids maintained. Patients who report the greatest benefit from binaural aids are those with more severe degrees of hearing impairment and those with more demanding and dynamic listening environments (such as crowded rooms) (Noble, 2006).

CROS/BiCROS hearing aids are also available, in which one side “pipes” sound to other side, where hearing is better. Some patients may prefer this option of BAHA; there is a lack of substantive trials comparing BAHA and CROS/BiCROS technology (Bishop & Eby 2010).

Cost of Hearing Aids

There are numerous brands and variants. In general, smaller devices, such as the CIC devices mentioned above, are more expensive, and newer/more complex circuitry is also more expensive. Compression circuitry in analog aides is more expensive (but definitely a good idea). Greater user control is also usually more expensive. Binaural aids are always better when there is usable hearing in both ears.

Many states have a 30 day tryout period, which is basically a legally mandated money-back guarantee for the hearing aid device itself. The dispenser is allowed to keep a fee for their services during the trial. As historically 2 out of every 3 hearing aids are not worn (at least not worn often), and hearing aids are generally not covered by insurance and typically costs in the thousands of dollars, we recommend that you think about this carefully.

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Cochlear Implants

An exciting recent development is an ability to provide hearing to some bilaterally deafened individuals through implantation of a device that directly stimulates the hearing nerve (spiral ganglion). Although this device is not generally considered as a hearing aid, it performs the same purpose for individuals with severe hearing impairment involving both ears. At this writing, 8/12, there are a few companies that make implants: Cochlear Corp., Advanced Bioinics, Med El Corp., and Neurelec (not available in the US).

Most neurotologists are able to perform this procedure. Cochlear implants do not completely substitute for a normally hearing ear, and at very best, may allow someone who was previously totally deaf to understand conversation on a telephone. Cochlear implant packages, including the device, surgery, and rehabilitation are much more expensive than hearing aids (roughly $45,000), but when one is indicated, they are generally covered by insurance, unlike the situation with hearing aids. A patient-contributed history is found here. Further information about cochlear implants can be found at the following sites:

Combined electrical and acoustic stimulation (EAS) uses a cochlear implant in combination with a hearing aid, and may be beneficial in some patients (Kiefer, 2005).

Regeneration of Inner Ear Hair Cells

Many processes that affect the inner ear kill hair cells, which are the main sensory part of the ear. While it would seem reasonable that hair cells should be replaced when they are lost, this seems to be somewhat species specific. Hair cells of birds, both auditory and vestibular, regenerate but hair cells of humans are generally felt to regenerate very little, if at all (Frucht et al 2011, Groves 2010), although there some promise has been shown for human hair cell generation via gene therapy (El-Amraoui & Petit 2010).

Research Studies on Hearing Aids and Regeneration

At the American Hearing Research Foundation (AHRF), we have funded considerable basic research on hearing aid technology as well as basic research related to hair cell regeneration in the past. Click here if you would you would like more information about contributing to the AHRF’s efforts.

References

  • Bentler RA. 2005. Effectiveness of directional microphones and noise reduction schemes in hearing aids: a systematic review of the evidence. Journal of the American Academy of Audiology 16: 473-84
  • Bishop CE, Eby TL. 2010. The current status of audiologic rehabilitation for profound unilateral sensorineural hearing loss. The Laryngoscope 120: 552-6
  • Christensen L, Richter GT, Dornhoffer JL. 2010. Update on bone-anchored hearing aids in pediatric patients with profound unilateral sensorineural hearing loss. Archives of otolaryngology–head & neck surgery 136: 175-7
  • Cox RM, Schwartz KS, Noe CM, Alexander GC. 2011. Preference for one or two hearing AIDS among adult patients. Ear and hearing 32: 181-97
  • Cullington HE, Zeng FG. 2010a. Bimodal hearing benefit for speech recognition with competing voice in cochlear implant subject with normal hearing in contralateral ear. Ear and hearing 31: 70-3
  • Cullington HE, Zeng FG. 2010b. Comparison of bimodal and bilateral cochlear implant users. Cochlear implants international 11 Suppl 1: 67-74
  • El-Amraoui A, Petit C. 2010. [Stem cell therapy in the inner ear: recent achievements and prospects]. Medecine sciences : M/S 26: 981-5
  • Frucht CS, Santos-Sacchi J, Navaratnam DS. 2011. MicroRNA181a plays a key role in hair cell regeneration in the avian auditory epithelium. Neuroscience letters 493: 44-8
  • Groves AK. 2010. The challenge of hair cell regeneration. Exp Biol Med (Maywood) 235: 434-46
  • Hol MK, Snik AF, Mylanus EA, Cremers CW. 2005. Does the bone-anchored hearing aid have a complementary effect on audiological and subjective outcomes in patients with unilateral conductive hearing loss? Audiology & neuro-otology 10: 159-68
  • Janssen RM, Hong P, Chadha NK. 2012. Bilateral Bone-Anchored Hearing Aids for Bilateral Permanent Conductive Hearing Loss: A Systematic Review. Otolaryngology–head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery
  • Jenkins HA, Atkins JS, Horlbeck D, Hoffer ME, Balough B, et al. 2007. U.S. Phase I preliminary results of use of the Otologics MET Fully-Implantable Ossicular Stimulator. Otolaryngology–head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery 137: 206-12
  • Jenkins HA, Niparko JK, Slattery WH, Neely JG, Fredrickson JM. 2004. Otologics Middle Ear Transducer Ossicular Stimulator: performance results with varying degrees of sensorineural hearing loss. Acta oto-laryngologica 124: 391-4
  • Kiefer J, Pok M, Adunka O, Sturzebecher E, Baumgartner W, et al. 2005. Combined electric and acoustic stimulation of the auditory system: results of a clinical study. Audiology & neuro-otology 10: 134-44
  • Linstrom CJ, Silverman CA, Yu GP. 2009. Efficacy of the bone-anchored hearing aid for single-sided deafness. The Laryngoscope 119: 713-20
  • Miles RN, Hoy RR. 2006. The development of a biologically-inspired directional microphone for hearing aids. Audiology & neuro-otology 11: 86-94
  • Miles RN, Su Q, Cui W, Shetye M, Degertekin FL, et al. 2009. A low-noise differential microphone inspired by the ears of the parasitoid fly Ormia ochracea. The Journal of the Acoustical Society of America 125: 2013-26
  • Noble W. 2006. Bilateral hearing aids: a review of self-reports of benefit in comparison with unilateral fitting. International journal of audiology 45 Suppl 1: S63-71
  • Ricketts TA. 2005. Directional hearing aids: then and now. Journal of rehabilitation research and development 42: 133-44
  • Schiller JS, Lucas JW, Ward BW, Peregoy JA. 2012. Summary health statistics for U.S. adults: National Health Interview Survey, 2010. Vital and health statistics. Series 10, Data from the National Health Survey: 1-207

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