User:Roselamb

Hearing and Speech, An Incompatible Feature

This article exposes an incompatibility of the human hearing system to the most important function of speech, namely that it be understandable by the listener. When deafened persons using hearing aids say that they "hear but do not understand" it  delineates this incompatibility of hearing to speech. A major segment of hearing aid users find that just hearing sound but not understanding what is being said is frustrating to the point that their "aids" are frequently discarded. An analysis of human speech can provide the reason for this incompatibility.

For some 2.5 million years of pre-historical hominid existence, audible sounds were generated exclusively by means of air forced from the lungs and passing through the vocal chords. This was not fundamentally different from other animals who generated sounds in a similar manner, that is by means of air passing through the vocal chords. The basic ability to make sound was a key to survival of each animal specie and it retains this function into modern time.

The vocal chords are essentially vibrating membranes that can be controlled in pitch by the tightening or relaxing of muscles controlling these chords. Volume level too can be varied by controlling the amount and velocity of air passing through the vocal chords.

It was only in comparatively recent geologic time, perhaps 20 to 40 thousand years ago that an evolutionary development occurred exclusively in the world of the paleolithic hominid. There is no evidence that might explain what triggered such revolutionary development. What pre-historic hominid had created was a new set of sounds, quite recognizable and distinguishable from the more familiar sounds of the million year old language.

The true greatness of this evolutionary development lie not in the simple addition of a new set of sounds to existing sounds, but in the manner in which it was integrated into the older sound system. This became a coded system where using the original sounds with the new interleaved sounds could be interpreted by another humanoid who knew the "code" as meaning something happening in the past, or with a different one of the new sounds modifying the original language to be interpreted as something happening in the future. Modern grammar formalizes the manner in which speech is codified, by classifying speech into past, present and future tenses. With the coded duo-language  the basis for explaining historical as well as future events, planning on a new giant scale had it's roots. The monumental result of the new coded speech language was that the human specie gained dominance over all other animals.

How is this information related to the problem of the deafened persons being able to "hear, but unable to understand?" In the aging process, the hearing ability is reduced because of factors which are typically diagnosed as a reduction in high frequency response. Of far greater importance however, than the fact that a portion of the auditory frequency curve is reduced is the simple truth that the "new" or second language is significantly quieter than the older vocal chord language. That difference in sound levels can amount to as much as a thousand or more times, with the second, the newer language always the quieter of the pair. It logically follows that the quieter language would be the first one "lost" as a result of diminished hearing ability. And without the ability to hear one of the two languages constituting human speech, understandability of the "code of speech" is lost. An analogy one might consider is in attempting to understand the Morse Code, the "dit-dah language" without being able to hear either the short pulse "dit" or the long pulse "dah" of the code. It would not be possible. Distinguishable features of the two parts of speech languages can be described as tonal and the other as atonal, or, one as being sinusoidal the other, non-sinusoidal. A third possible way to describe differences of the two languages is to represent one as tones while the other as characteristic noises.

To examine why such major differences in sound levels between the old and new languages, one needs to examine how each is formed. As previously described, the original language of the vocal chords is mechanized  by air passing through the vocal chords and causing vibration of the chords resulting in  sound being created. Such a system has huge sound volume producing capability, many decibels greater than that of the second language. Also volume is highly adjustable in the first language. The "new" or second language is produced in most part by the shaping of the mouth and tongue with no vibrational effects or stream of air involved in the process. From a practical viewpoint, there is no actual amplification. To make the new language more understandable with no available adjustment features as in the first language, it becomes necessary to improve on the quality in the formation of that language. That involves an increased amount of distorting of facial muscles in order to provide improved quality of diction.

In summary, there exists two distinct sound systems comprising human speech. The two systems are pieced together in coded fashion. The two languages differ significantly in volume levels that can be produced, resulting in the weaker of the two being the first to be "lost" when hearing capability becomes lessened. As a result of the above observations, a meaningful solution to the needs of a typical aged, deafened person is an "understanding-aid", an aid which amplifies just the weaker of the two languages, the consonants. A new Understanding-Aid would require little or even no amplification of the sounds of the first language, the vowels.

Considerations of "consonant amplification" apply to many other applications as well, for example when used in radio and television broadcasting, speech would become markedly more understandable, i.e. clearer. So too, the spoken word in the lyrics of opera, would be made understandable by applying the techniques of "amplifying the consonants."

The deafened and normal hearing listener might with "consonant amplification" sit side-by-side and both comprehend the "code of speech."