The Case For Binaural Amplification:

Two Ears are Better Than One

What is meant by hearing impairment? It means that auditory stimuli are not loud enough to be heard and/or understood, that certain frequencies are missing in a listener's communication. He does not hear sufficient speech components of words, sentences and other speech stimuli. Words no longer sound like themselves; they become distorted. For an individual with a high frequency loss, what is missing, distorted, or modified are the high frequency, low intensity consonants. These include /s/, /f/, /t/, /th/, /f/, /sh/, /ch/, /k/, and /p/, as they appear in such words as sit, face, thick, fish, check and past

Such individuals experience and demonstrate difficulty in discrimination or word recognition and complain of having difficulty understanding what is being said to them. This applies to many, if not most of those individuals who have hearing loss.

Amplification appears to be the solution for the hearing-impaired individual who experiences permanent sensorineural hearing loss. Years ago audiologists and hearing aid dealers fitted such individuals with one hearing aid, and sent them on their way, to hear better with this new device -- and indeed, many individuals reported hearing and understanding much better with their prosthesis.

Over the past number of years, however, research has begun to show that there appears to be a problem with monaural amplification. The most obvious problem is the loss of the sense of directionality due to uneven stimulation at the level of the individual ears. one needs approximately binaurally symmetrical hearing in order to tell the location of a sound source.

A larger, more problem seem to have appeared. It is being referred to as auditory deprivation of the non-aided ear. Research suggests that non-amplification of one ear constitutes a form of monaural auditory deprivation. That is, as one ear hears and understands better, it becomes the dominant organ of hearing, and the unaided ear is deprived of stimulation. No longer is speech made loud enough for that ear to hear, because the aided ear hears at a lower loudness level. No longer is an effort made to speak to that ear, because the other ear performs better.

What studies have shown is that when monaurally aided individuals are reevaluated audiologically after a few years, pure tone thresholds in both ears remain approximately the same. Speech discrimination ability, however, shows different results: discrimination remains stable in the aided ear, while it shows significant decrease in the unaided ear. In other words, by not aiding both ears, we seem to be creating a situation in which the speech discrimination in the unaided ear deteriorates. Such lopsided deterioration cannot be attributed to aging effects - not on one ear only. Some researchers have gone so far as to suggest that the unaided ear loses more speech discrimination ability with the other ear aided than it would have had neither ear been aided at all. It also follows then that the longer an individual wears only monaural amplification, the greater the decrease in speech discrimination will be.

This is a strong argument for binaural amplification. The underlying thought here is that two hearing aids would restore the auditory system to the best approximation of the original system. It has even been suggested by some researchers that the unaided ear, if it then acquires amplification, can improve in speech discrimination ability. If the purpose of evaluation and intervention in the form of recommending amplification is primarily to assist the patient in achieving better means of communication, then we must consider this argument seriously.

The point here seems to go beyond the idea that two ears hear better than one. More to the point: the sum of the whole (binaural amplification) is significant greater than the sum of its parts (monaural amplification and deteriorating speech discrimination in the unaided ear).

Consider also that one particular research group, responsible for much of the testing in this area, has subjective reports from hearing impaired subjects that they note a significant decrease in communication effort. This report, by itself, is a strong argument for binaural amplification.

(The issue of "amplification: yes or no" is not the issue here, but consider this, if an unaided ear deteriorates greater than the aided ear because of auditory deprivation, what is the experience of the totally unaided individual who is experiencing auditory deprivation in both ears? Hospital case files show example after example of older individuals with hearing loss who return. for reevaluations: pure tones remain constant, speech discrimination drops off year after year in individuals who resort not wanting or not "needing" amplification.)

Binaural amplification is not just to pad the profits of the hearing aid dealers. Research shows that there is a definite benefit to binaural amplification, and an apparent disadvantage to monaural. Again, if improved hearing and better communication is the goal for our patients, we must take this argument seriously and encourage our patients to try and obtain binaural amplification. Two ears are better than one.

Silman, S., et al.: "Late onset auditory deprivation: Effects of monaural vs. binaural hearing aids." J.Accus.Soc.Amer. 76(5):1357-1362 (1984).

From the files of THE GERMANTOWN HOSPITAL AND MEDICAL CENTER

Blue Bell Hearing Aid Center, Inc.

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