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Hearing aid technology that will work for you depends first of all on a good hearing test. Then you will be fitted with amplification that is appropriate for your individual needs. A "one-size-fits-all" hearing aid does not work for most hearing losses. Hearing aids have come a long way recently, with the advent of micro-technology. We are able to place more circuitry in a smaller package. Hearing aids now fit deep within the canal and have internal controls which automatically adjust in extreme noise conditions. No hearing aid can work as well as the one God created, but with the new technology we are getting closer.
The Hearing Test
First, you need to know what constitutes a "good" hearing test. A complete hearing test consists of the following components: Pure Tone Air Conduction test, a Bone Conduction test, Speech Reception Threshold test, and a Speech Discrimination test.
- Pure Tone Air Test
- Many of you are probably aware of "Pure Tone Air Testing". This is when a tester places headphones over your ears and plays different tones. You are told to indicate when you can hear each tone. This test will determine how well you hear at different frequencies. The normal human ear can hear tones from 20 to 20,000 cycles per second.
- Bone Conduction Test
- During the Bone Conduction test an instrument is placed against the mastoid bone, which is just behind your ear. The tester then plays the same tones as you heard during the Pure Tone Air testing. You must indicate when you hear the tones. This test will determine whether your hearing loss is due to outer or middle ear problems, or inner ear nerve damage.
- Speech Reception Threshold Test
- The Speech Reception Threshold is the softest point at which you are able to repeat words correctly fifty percent of the time. The Speech Reception Threshold test indicates the volume you need before you can hear and understand words.
- Speech Discrimination Test
- In the conventional Speech Discrimination test, the hearing specialist presents 25 to 50 standardized words to you, which you are asked to repeat. Word discrimination testing serves three purposes:
- Test words given at normal speech levels indicate how the client is functioning without hearing aids.
- The client's best speech discrimination is found by testing at different intensity levels to locate the level which produces the best score.
- Speech testing gives you an opportunity to hear the benefit you will receive from amplification.
Conventional hearing aid electronics use basic analog Class A technology to provide quality, linear-type amplification. Class A amplifiers have the characteristic of adding the same amount of amplification to all levels of sound intensity. Therefore, low bass sounds will be amplified with the same amount of volume as high treble sounds. Some patients may find that conventional electronic hearing aids provide either too little sound or too much sound to comfortably reach a listening level for the particular hearing loss. This is especially true if you have an high frequency hearing loss. Conventional electronics represent the most basic type of amplification and are a good choice when finances are the major concern. They also are adequate if the user is mainly in quiet situations and only talks to two or less persons at a time. Many who are house bound can be helped with this type of circuit which is very reasonably priced.
Advanced Technology Circuits
Advanced Technology Hearing Aid circuitrys employ a more recent scientific development in amplification electronics known as non-linear or compression amplification. The result is a hearing aid with the ability to limit the level of incoming sound volume. This delivers a more natural loudness throughout the patient's entire listening range, without getting too loud or too quiet as can be the case with conventional hearing aids. Amplifiers used in advanced technology hearing aids are predominantly from the Class D family with the benefit of longer battery life and lower distortion.
Circuit designs used in instruments can include: automatic signal processing, base increases at low levels; automatic signal processing for gain control input or gain control output. Advanced technology hearing aids can also employ multi-channel technology, multiple directional microphone technology and variable release compression. Patients with a mild to moderate-severe hearing loss, those with a high frequency loss and those with reduced tolerance to loud sounds benefit from these circuits. The sounds heard are more balanced and natural sounding. There is less distortion of sounds. These circuits are available in all the different sizes of hearing aid shells.
Miniaturized Technology
Micro miniaturization of circuitrys has reached the ultimate in small size within the past two years. Tiny hearing aid shells called Deep Canal, MicroCanal or CIC (completely-in-the-canal) have been developed. The majority of these instruments use Class D or K-AMP circuitry. Class D amplifiers offer longer battery life and lower distortion, while K-AMP amplifiers are designed to amplify soft sounds. These components are placed to take the least amount of space in the shell. This allows the instrument to be inserted deeply into the ear's canal. This makes the hearing aid virtually impossible to see. Patients who do not want to be seen wearing a hearing aid benefit greatly from the micro-technology. Also patients with an active lifestyle benefit greatly, since there is almost no "wind noise," and the wearer is able to talk on the telephone without any feedback noise. The wearer is also able to exercise and do vigorous work without losing the hearing aid. You are able to wear the aid during sleep, thus the patient can continue to hear important sounds such as speech or alarms. Also less power is needed because of the instrument's close position near the eardrum.
Digital & Programmable Instruments
Programmable hearing instruments are a great technology advancement. These instruments contain a computer chip which can be programmed by the hearing specialist using a computer. This offers a better way to accommodate a given patient's amplification needs because it allows the greatest flexibility and most fine-tuning capability. This unique technology separates the incoming sound into bands and processes each band independently. This class of hearing instruments utilizes separate circuit paths to independently process different frequency regions of sounds. Most of the programmable hearing aids feature variable volume, adaptable frequency response, adjustable and optional input or output compression.
These hearing aids automatically achieve more volume for the soft, high frequency sounds and less volume for the more intense, low frequency sounds. The major advantage is that the instruments can be adjusted as the patient's hearing c hanges over time, therefore you should not have to buy another new hearing aid as frequently. The Digital Sound Processing circuits are truly the greatest advancement in the hearing industry. The analog sound is changed into a digital format. This is where all the sound processing is done. The digital circuits also do "sound sampling", which means they listen for steady state noise and are able to dampen some of the background noise and enhance the speech sounds. You can notice this feature when you are around machine noise, or when traveling in a car, the road noise should be less of a problem. Most digital processing circuits have multiple channels, so that your hearing specialist will have a much better ability to fit your hearing loss.
Today there is a wide range of choice for the hearing aid user and also a wide range of price. We can't explain all there is to know about current technology on this page. But we hope this short paper will help you realize how important hearing is and the importance of a proper hearing test and fitting. If you have any questions just send us email.
© 2000 Speech & Hearing Clinic of Huntsville
info@hearingandspeechclinic.com
303 Williams Avenue, Suite 1111
Huntsville, AL 35801
phone: 256.536.7405
fax: 256.536.7416