- 1. Introduction
- 2. The anatomy and physiology of hearing
- 2.1 The anatomy of hearing
- 2.2The physiology of hearing
- 3. Deafness and hearing loss - what it means and its reasons
- 3.1Definition of deafness and hearing loss
- 3.2Reasons for deafness
- 3.2.1Inherent reasons/ prelingual reasons
- 3.2.2Acquired reasons/ perinatal and postlingual reasons
- 3.3Ways to "cure"?
- 3.3.1Hearing aids and the Cochlea Implant
- 4. The study of the University of Washington
- 4.1Description of the study/research
- 5. Evelyn Glennie
- 5.1A short biography
- 5.2Her way of living
- 5.3Evelyn Glennie"s music
- 6. Conclusion
Can deaf people "hear"? - No, of course not, they are deaf! But it is not that simple, as I found out. Even I used to think that way, too, but a very special woman changed my view - Evelyn Glennie, a profoundly deaf musician. She will later appear as an example in this work. Many people think that deaf people live in a world of almost complete silence and they think like that without knowing a little bit of background information, but what is even more problematic: how can a hearing person judge about it? Actually it is difficult to know, still some people persuade themselves to be in the position to really pass judgment on it. When I first heard of Mrs. Glennie I was especially interested and immediately wanted to know more, find out more. Is she telling the truth? Or is she imagining impossible things? Because it is hardly imaginable for us "normal" hearing people how someone who is biologically deaf/ hearing impaired still should be able to hear. For that reason I started to research, and it is why I chose that difficulty as the topic for my research paper: Can deaf people "hear"? - The perception of sound referring to Evelyn Glennie. The aim of the research paper will be to erase prejudices as well as coming closer to the world of hearing impaired people in order to understand them better, of course I"m also trying to find the answer to the question. Therefor, I will explain the hearing of not hearing impaired people first. Then the examination of deafness and hearing loss follows. And finally, if deaf/hearing impaired people are able to "hear"... or not.
2 The anatomy and physiology of hearing
Before starting to discuss about deafness a few questions should be answered beforehand: what is hearing? Whereby do I hear? Just with the ears? Or is there more? How does the hearing work? What process is behind it? To answer all these questions I will describe the anatomy and physiology of hearing in the following.
2.1 The anatomy of hearing
The hearing organ consists of the external auditory canal, the middle ear, the inner ear, the auditory pathway and the auditory cortex (see appendix, fig. 1, page 15), but what might sound simple and clear actually is - like so many things in biology and medicines - much more complicated. In the following text passage the anatomy of the hearing organ will be outlined a little more detailed. Working ones way through from the outside to the inside the external ear is incipient, it is what one can view most likely from the outside and what roughly collects the sound. The external auditory canal ties to it, it passes on the sound waves to the eardrum which is stretched at the end of the hearing canal and which forms the border to the middle ear. The tympanic cavity adjoins the eardrum. The auditory ossicle - malleus, incus and stapes - as well as the Eustachian tube as a thin "passageway" directly leading from the tympanic cavity to the oropharynx are located in the tympanic cavity. The stapes is embedded in the oval window with its footplate and therefore is the transition to the inner ear. The inner ear is a complex labyrinthine construction with many canals and hollows, the osseous labyrinth, which is filled with a liquid. In the osseous shell the membranaceous labyrinth is enclosed. The membranaceous labyrinth includes both the vestibular organ and the hearing organ. The vestibular organ, consisting of three semicircular canals (the anterior, the posterior and the lateral semicircular canal) and the vestibules, ties through the cochlear canal to the "coiled" cochlea. The cochlea has two exits or entrances: the oval window and the round window, which, just like the oval window, leads to the tympanic cavity of the middle ear. Back to the cochlea, in which also the basilar membrane is. The basilar membrane contains among other things the organ of Corti with circa five thousand sensory cells, inherent inner and external auditory cells. In the spiral cochlear ganglion the hair cells become synaptically connected with neurons. From there the cochlear nerve and the vestibular nerve head to the brain stem together. The auditory pathway, which began at the organ of Corti and the sensory cells, leads on to the auditory cortex, where sound information is processed. The auditory cortex sits in the temporal lobe of the brain.1
2.2 The physiology of hearing
So, now we know how the hearing organ is up, but what still is in the dark is how it works. Hearing simply said is the perception of sound waves in different variations, trebles and gravities. Every single tone is sound in reality, just like music, spoken language, noise. Sound are pressure fluctuations (pressure waves) in the air that can be perceived by the ear, these fluctuations are metered in Hertz. Therefor one differentiates between tones, these are pure sine oscillations, clangs, i.e. normally a fundamental tone and various harmonics or overtones, and noise, a multicolored, diverse and multifarious composite of many frequencies. That means a noise are several clangs and a clang are several tones. And how does the sound reach the auditory cortex? That small sentence already anticipates a lot because the auditory cortex is the "final destination" on the way of the sound, one already knows that. It starts with the external ear. The sound passes over the external ear further through the external hearing canal to the ear drum, with which the middle ear begins. The middle ear makes it possible for the sound to enter the inner ear. The sound would be reflected without the "help" of the middle ear, the consequence of that would be that one could almost hear nothing, of which more later. The ear drum is put into oscillations by the sound so that these oscillations again put the malleus, the incus and the stapes into oscillations, in other words from that point the sound is transferred over the auditory ossicle to the inner ear. Furthermore the auditory osscile match the low impedance, which means low drag, of the air to the high impedance of the fluid-filled inner ear. If that matching would not happen, the sound would directly without any impediments dash against the oval window of the inner ear. Because of the impedance discrepancy the present liquid there would not be put into oscillations and that would entail a reflection of a huge amount of the sound. Only around two percent of the sound waves could enter the inner ear and actually be perceived in the end. The sound has arrived in the inner ear and generates oscillations at the basilar membrane in the cochlea. Due to the steady movement of the stapes because of the incoming sound waves the membrane of the oval window is constantly moving consequently also the basilar membrane and the liquid in the cochlea is in a constant up- and downward vibration. Through these shifting movements the small sensory hairs of the auditory cells in the organ of Corti, which quasi is directly located at the basilar membrane, are directed outwards and inwards, this happening is called deflection. Not aroused auditory cells have a so-called resting potential. When the auditory cells are in the state of deflection, the membrane potential changes and converts or transduces from the original mechanic signal into an electric signal. The change of the membrane potential is called sensor potential. That sensor potential leads to the exposition of afferent transmitters, to the goal leading messengers like glutamate, in the inner auditory cells. These transmitters reach corresponding receptors in the cell membrane of the afferent auditory nerve cell after the diffusion in the synaptic cleft. A chain of neuronal excitations starts and leads as the auditory pathway over the auditory nerve and the brain stem to the auditory cortex in the temporal lobe of the brain. Through these neuronal excitations the previously converted information of the sound signal is transferred to the auditory cortex, as a part of the central nervous system, over at least five to six series-connected neurons (cells that are specializing in the transfer of certain excitations). Several neurons are specializing in various areas. Thus there are neurons for the spatial hearing and superior neurons for complex sound patterns like for example phonemes of the language. In the auditory cortex information are interpreted as music, language, ... In fact only a small part of auditory/acoustic information gets to the auditory cortex, the sound that contains the important, wanted and needed information is transferred (target sound) while disturbing noises, therefor superfluous sound information that are not of use, are eliminated during the information processing. One can see that by reference to the spoken language: the spoken language is the information that one uses or needs, it is the target sound. Words of speakers that one is not interested in or annoying background noises whereas are superfluous and not of use in this case so they get eliminated. That discrimination happens through specialized neurons, too.2
3 Deafness and hearing loss - what it means and its reasons
Now it is clear, what hearing is - but what is not hearing or partially hearing? What does deafness and hearing loss mean and where do the losses come from? And how can one "move in on it"? These questions introduce the next difficulty and hint forward to the core.
3.1 Definition of deafness and hearing loss
Deafness can be inherent or acquired, that means it can be prelingually or perinatal and postlingually. It characterizes the condition of an entire or a partially, great or profound loss of the hearing ability, thereby one differentiates between two kinds of deafness: the absolute Taubheit and the praktische Taubheit. The absolute Taubheit goes for the loss of hearing for all auditory stimuli, which means the person affected does not hear anything. That can lead to an impaired speech development depending on when the deafness occurs, deaf-muteness (no normal speech development despite an intact speaking apparatus due to various deafness kinds) is often the consequence of inherent absolute Taubheit or absolute Taubheit before the eighth year of life. The praktische Taubheit characterizes a very profound hearing loss, the person affected does not perceive sound until a sound intensity of seventy decibel. That makes normal communication almost impossible, only "single" noises can be perceived fractionally.3 4 All other forms and kinds of a partially loss of hearing fall within the scope of hearing loss. Similar to deafness it can be inherent or acquired. Hearing loss can be bilateral or unilateral and it can be temporary, so that it goes away after a while on its own, depending on what kind of hearing loss one has, the conductive hearing loss. Here, too, one can differentiate between two kinds of hearing loss: the sound conduction hearing loss (the harm is in the external auditory canal and/or in the middle ear) and the sensorineural hearing loss (the harm is in the inner ear, between inner ear and auditory cortex and/or in the auditory cortex). A combination of both is possible as well.5
3.2 Reasons for deafness and hearing loss
The reasons for deafness and hearing loss are numerous. Mostly, the very same reasons, according to the degree of the loss of hearing, can cause deafness and hearing loss. Basically it is the easiest to differentiate between two larger reason-areas: the inherent and the acquired deafness/hearing loss.
3.2.1 Inherent reasons/ prelingual reasons
Prelingual reasons cover all these that lead to a harm in the area of the hearing organ before the child is actually born. These reasons can be...
...inherited. Both the mother and the father "suffer" from deafness, passed on from one generation to the next, like the color of the eyes or the hair. The harm is not avoidable and it cannot be traced back to impacts from the outside.
...infection-related. During the pregnancy the mother suffered from an infection like mumps, measles or rubella, it can lead to an abnormal development of the child.
...disease-related. The mother has a disease, for example she is diabetic. The disease of the mother may entail an abnormal development of the child, too.
...medicamentous. While the mother was pregnant, she took wrong doses of medicaments or false medicaments what can interfere the development of the child and have negative consequences.6
3.2.2 Acquired reasons/ perinatal and postlingual reasons
Acquired reasons for deafness or hearing loss can be perinatal, that means they occur in the course of birth, or postlingual, so they happen as life goes along. Anyway, oxygen deficits of the child, a small birth weight, a blood group incompatibility between mother and child as well as neonatal jaundice are known as possible perinatal reasons. Postlingual reasons are the most common reasons for deafness and hearing loss as they are the case for more than half of the people affected. They occur after birth, in turn that does not have to mean that they only happen whilst one is still a young child but rather cover the adult groups and senior groups, too, so the age-related hearing loss. Although this kind of hearing loss is not only explainable with the following circumstances, they accelerate and encourage it. However, things like vaccination damages, external forceful impacts like punches that entail a cranial trauma (but which can also be caused by falls), noise damages through too loud noises from the surroundings (music, gunfire, construction works, ...), infections (scarlet fever, measles, pertussis, tuberculosis, ...), metabolic diseases (cretin, endemic deafness), inflammations and many other external influences can lead to losses. Some of the named losses may be progressive - they progress further and worsen their condition (till deafness). Losses of hearing ought to be recognized as early as possible to avoid further harms, that is even more important when it is about losses in infancy. It is striking when children "suffer" from losses of hearing, their behaviour is unusual, for example reticence, no imitated "babbling" or no reaction to calls of the name and address. With the help of hearing screenings and reflex- or behavioural audiometers it is easy to diagnose them. Unfortunately, the diagnosis is often made too late.7
3.3 Ways to "cure"?
This point divides the minds. Some deaf people and people with hearing loss think of healing methods as discriminatory - why should one get cured if one is not ill? But for others again the healing methods from nowadays are a sheer blessing. Some people affected are fine with the community of deaf and people with hearing loss or do not have problems with communicating with normal hearing people, while others think of hearing aids, e.g., as a way back into society with social contacts and out of isolation. Whatever one"s point of view might be, it is a fact that meanwhile, people with a loss of hearing can thoroughly live a wonderful life, be it with or without help.
3.3.1 Hearing aids and the Cochlea Implant
If a loss of hearing is considered, it should be diagnosed by a doctor and, at least, a person with the right knowledge should be consulted, where a treatment is recommendable. Drugs are prescribed depending on the degree of the harm, like among other things the auditory canal may be cleared or antibiotics may be prescribed if one has an inflammation, or like foreign bodies will be removed (extirpated) in the case of an infestation of foreign bodies, tinnitus can be cured through several treatment options according to the severity. However, there are many reasons for losses in the area of the hearing organ and even more treatment options, but this text will focus on only two of them: hearing aids and the Cochlea Implant. Beforehand, hearings aids are only prescribed if no other healing methods help anymore. Their main function is to undertake, intensify or enhance several functions, mostly hearing. The CROS hearing system for example is a hearing system "that transfers sound information which cannot be processed by the deaf ear anymore to the other ear through a tiny microphone whereby among others an improved directional hearing is enabled"8. Actually every hearing aid has the same basic principle: a microphone intensifies the noises from the surrounding world on the analogy of the degree of the hearing loss, so that one can hear enough and appropriate. Nevertheless hearing aids can only help people with hearing loss or maximally with a praktische Taubheit. Still, deaf people do not have to give up on hearing just because of that. Since a few years another option appeared. The Cochlea Implant brings along new possibilities, it can help perceiving sound again, but one must meet certain "requirements" or else the inner ear implant will not have any effect, which are: an intact auditory nerve and not intact sensory hair cells as the reason for the deafness. This seriously limits the set of treatable people, moreover the implant is not suitable for older deaf-born people, it is most effective on young people and children. The implant itself is put in the cochlea and sometimes in the round window where it replaces and undertakes the function of the sensory hair cells.9
4 The study of the University of Washington
It seems like there are many ways to live with deafness or with a hearing loss, be it with hearing aids or through an implant-surgery. But some deaf or partially deaf people do not make use of them. One self as a normal hearing person immediately wonders: why, how can one even live without hearing? On the one hand: some people were born deaf, they do not know what it is like to hear or to sense sound or in other words they never had the pleasure to hear, you cannot miss what you never had. On the other hand some people are perfectly fine with their deafness/ hearing loss and do not think of it as a disability, they are content without hearing aids and implants. Some people who got deaf later in the course of the years learned how to speak and can read lips, others, also people who were born deaf, use sign language. And... there are even deaf/partially deaf musicians. Even though one thinks that hearing is the basic ability to make music and to sense music it is actually not. It might be a little more complicated from our point of view, but exactly that narrow-minded opinion is our disability and limitation.
4.1 Description of the study/research
In 2002 a research was published at the University of Washington. That research deals with the before written theses, that also deaf people can sense sound, and undergirds it through facts and experimental results. The project leader Dr. Dean Shibata needed twenty-one volunteers including ten deaf and eleven normal hearing people. Gender, age, nutrition and the like of the probands are unknown. With the help of the functional magnetic resonance imaging (procedure of exploring for drawing up cross-sectional images of the human body with the use of the nuclear magnetic resonance10) brain activity could be observed during the experiment. While scanning the brains the probands were submitted to intermittent vibration stimuli that were supplied over the hands. In the course of the experiment both deaf and normal hearing experimentees showed a brain activity in the area of the post central gyrus, the part of the brain that among other things senses touch, pressure, vibrations and temperature. The deaf participants additionally showed brain activity in the area of the superior temporal gyrus. The auditory cortex is located in that area, that also got active. The normal hearing did not show that extended activity.11
But what does that mean? Apparently, that shows the research, there is a neuronal connection from the area of the brain that is competent for vibration, pressure, etc., to the in the temporal lobe located area that senses auditory stimuli, the auditory cortex. According to Shibatas assumption "all the parts of the brain will be used to maximal efficiency."12 Hence it is possible, that if the original purpose of the auditory cortex, the perception and interpretation of auditory stimuli, is canceled or partially dropping out due to deafness/hearing loss, that part of the brain is used for different, similar functions. That would be much more efficient than completely shutting down a whole area of the brain. Like that the brain can develop accordingly, so that the auditory cortex interprets vibrations acoustically instead of the proper incoming auditory stimuli and refers to these vibrations with the potential sound of things, the auditory cortex is allotted to a different task so to speak. It would explain why deaf/ partially deaf people can make music, too, enjoy concerts and musical events in some sort and maybe also can connect vibrations, leading from everyday noises, with the world and happenings around them up to a certain extent.13
5 Evelyn Glennie
In fact, there are many hearing impaired people who made something out of their lives, who did not get discouraged from others and from their "impairment". People, who realized just what Dr. Dean Shibata realized with his research: that being hearing impaired does not necessarily have to be a so called disability unless one thinks of it as one, unless one defines himself over a harm, unless one lets himself being suppressed and categorized by a framework created of the squishy belief of clueless people. A living proof for this is Evelyn Glennie. She is a famous and fabulous musician, mainly percussionist. Actually, she is profoundly hearing impaired but never hang a lantern on it. From her point of view, she perceives sound like everybody else - through her body.
5.1 A short biography
Evelyn Glennie (see appendix, fig. 2, page 16) was born in Scotland, Aberdeen, in 1965. She grew up on a farm with her parents, her father has always been an important source of inspiration for her, and her two brothers. Already with the age of eight Glennie started playing the piano but by reaching the age of eleven/twelve her sudden aggravation of hearing impairment brought her to the phase of needing a hearing aid. Later when she was about to go to secondary school an otologist would have almost ended her development to a musician. He told her that she was hearing impaired, that she needed these hearing aids and that she should go to a school for the deaf. For Evelyn, it was absolutely not understandable, she never has had the feeling of not being able to do something due to her "disability" until then but after a simple visit to the doctor she suddenly should not be able to do anything anymore, because someone told her what disabled people cannot do in the common comprehension of people - Glennie continued going to her old school, she used hearing aids but kept participating in the normal lessons. After a while percussion aroused her interest and in the course of playing she realized that by taking off the hearing aids she would hear less through her ears but more through the rest of her body. Evelyn Glennie kept on making music during her youth and spent a lot of time on training and refining her ability of detecting vibrations - "the beginning of really using the body as some kind of resonating chamber"14 - with the help of her percussion teacher. That was also the time when her ability to perceive sound waves has reduced to twenty percent of the original capacity, the way it remained until now. In 1985 at the age of 19 she graduated from the Royal Academy of Music in London with and honour degree. From then on Evelyn Glennie"s career as a musician and professional percussionist really started. She collaborated with several musicians and music groups such as Sting, Fred Frith, the Taipei Traditional Chinese Orchestra and much more; her music is featured in films, radio programs, television, and music library companies; her solo recordings exceed twenty-eight CD"s; Glennie is also a teacher, inspiration and adviser for many people. She won over eighty-six international awards, gives more than one-hundred international performances a year and can call herself "the first person in musical history to successfully create and sustain a full-time career as a solo percussionist"15.16
5.2 Her way of living
It is music what fills Evelyn Glennie"s life with sense, what makes her matter as a human being, something that was known to be the essence that is only accessible for hearing people. How can this be? In reality, it is all about the attitude with which one faces something. Although she might be hearing impaired it does not affect her life as much as it arouses the interest of media, one can say that it nearly does not hinder her from doing what she wants to do in anyway. Sure, she has to put a lot of effort in her work with music - but so does every other musician, too, it is not at issue for her to define herself over something that is totally irrelevant. Would you define yourself for example over your hair color? The fact that one lives with inconveniences is normal, one learns to live with it and it becomes naturally. As a musician, Glennie needs to listen to music, the inferred question of anyone normal hearing at this point would be: how does she hear what she is playing and doing? - Like everybody else, with her body. First of all, she still has left a little bit of her original ability of hearing, but that is not her main intake source, even more it is subsidiary. Moreover, she listens with her whole body. Due to her vibrations detecting training she is much more open to feeling frequencies than others. It is her belief that actually everybody can feel these vibrations, for example also higher frequency vibrations that appeared to be much harder to detect than the lower ones, but the hearing organ takes over the role of "listening" more and more the higher the frequency gets because it seems to be more efficient and therefor the feeling of these vibrations is blinded out. So, the original sense of hearing indeed limits our possibilities. Only when some senses may disappear the extended functions of the other senses get a chance. For that reason Evelyn Glennie said "being a musician, being a dancer, being an artist [...] is all about the sense of touch, really. The form of communication is about touch and I don"t literally mean (touches her arm roughly) that kind of thing. I mean touch is just something so vast [...], we need all our senses for the others to function. [...] To take away the eye, it"s not a big deal, to take away the ear, it"s not a big deal, all the other senses will become that particular sense that you"ve lost. [...] This is what the mysterious "sixth sense" is about, it creates a type of sense that we never knew it existed until the one of the other disappears."17 Evelyn was able to refine her sense of detecting sound through vibrations so far that she can differentiate between low and high sounds, i.e. that she mainly feels the low sounds in her legs and feet and the high sounds on places of her face, neck and chest. However, this is basically, among other things, what makes her being able to live like everybody else. In fact, interestingly, she sometimes is even irritated and feels unbalanced from the loud sounds of her surroundings, unimaginable for hearing people that deaf people or people with a hearing impairment feel disturbed by noises from time to time that most of the people think of as normal and know as their daily background noise. Also, Evelyn Glennie does not use a hearing aid. Like mentioned before, one gets used to things, they become naturally, according to that, she found her way to deal and live with it. With the help of the bit of sound she understands and lip-reading Glennie masters her way through everyday life. No one would probably recognize her as someone who is profoundly deaf, also because she can speak like a normal hearing person. Moreover, she claims that it is possible to imagine a sound when seeing some things, that one connects a specific sound to what happens around one, so does she. For example she imagines the rustling of leaves when she sees them moving in the wind. Anyway - who decides how things sound? Is it sure that we all hear the same? No, it is absolutely not because every single one has an individual perception of what he/she experiences. Evelyn Glennie found that out, too, and that undergirds her idea, that even deaf people do not live in a world of silence. Maybe, or rather definitely, they hear things but only different from normal hearing. All these thoughts support and help Dame Evelyn Glennie to be the person she is. She does not like to discuss about deafness because that is the task of an otologist - her specialty is music.18 19 20
5.3 Evelyn Glennie"s music
Evelyn Glennies main activity (and occupation) is being a musician or creating sound. Making music is her passion, something like her purpose, and if one ever heard and saw her performing one will immediately believe it. Her sounds are very spherical and full of emotions. They invite one to a journey and make one imagine very far scenes and images, it is Glennies other way to communicate with people: through music. Of course the instruments she uses create lots of vibration and rhythm next to sound. Hence she owns circa 1800 instruments, including xylophones - six marimbas - , snare drums and much more, but she also uses ordinary things, for instance kitchen ware or tin cans, chopsticks, hammers, etc. to make sound and in the end music. As mentioned before, her whole body acts as a kind of resonance chamber respectively sound box, that means she detects the vibrations on/in her entire body with the neck, chest, feet, legs and the like, this ability builds the essence or basic module that allows her to be a musician, but also her strong will and belief just as her seemingly unlimited imagination play a very important role. The Scottish musician can often be seen performing bare-footed, that makes the feeling of the vibrations more intense but it also gives her the feeling of being more connected to the sound, or playing the marimba with two mallets each hand. In general, Evelyn has developed a rare unique and individual way of making music.21 22 23 24
In the end, to sum up, one can say that average people perceive sound with their hearing organ, the external auditory canal passes on the sound, the sensory hair cells... et cetera and deaf and hearing impaired people are known to not be able to hear or to only perceive sound in a limited way. Hearing aids may support the process of hearing and enhance the quality of the sound. But deaf can also "hear" differently. Indeed it has not much to do with the original process but it is likely that if some senses and perception functions drop out or disappear, the brain tries to replace the lost senses (with other senses) the best it can and remaining senses become even more intense, too. Corresponding, hearing impaired have a high auditory reaction to vibrations, the research of Dr. Dean Shibata as well as the description and experiences of Evelyn Glennie prove that. Folks with deafness or a hearing loss may imagine a sound according to the type and intensity of the vibration frequency. Unfortunately deaf people are constantly underrated due to their differentness without really going in for a closer look, being different does not have to have less intelligence and disability as a consequence, quite the contrary is reality. Isn"t it fascinating how people with a so called disability deal with it and make the best out of it? Deductively, the perception of sound has way more issues than just what normal hearing call "hearing". If one includes the ideas from before in ones way of thinking, deaf/hearing impaired people can actually sense sound, only with the additionally use of other parts of the body (the neck, the legs, the hands, ...). What it is like to perceive sound as people like Glennie do, regardless of hearing aids, is hard to reconstruct and understand for human with an intact hearing organ. Still, if the auditory cortex is really interpreting the vibration information comparable to the sound information, it cannot be that different. Sound in general is hard to define clearly because how everyone is an individual person everyone hears individually, no one perceives or interprets the noises around one the same as the neighbor does. The biological process between normal hearing is equal, but the result certainly not.