To quote Prof. J.C. LAFON:

« The level of hearing impairment opens various prospects.

Naturally, the hearing threshold is only one of the characteristics that allow sounds to be perceived by human beings based on their spectral composition. In other words, that information only tells us there may be a signal, but by no means whether that signal is perceived properly, if it is identified properly, and all the less so if it is useful in understanding the global message. Actually, those levels, calculated and expressed in decibels, provide information on what cannot be perceived: they provide adverse data.

It is generally acknowledged that hearing devices only become necessary for patients to perceive their surroundings when the general impairment reaches a level of 35 dB of hearing loss, and a level of over 30 dB of hearing loss in the 2000 Hz octave band. And vice versa: hearing aids are considered to be properly fitted and to provide a reliable improvement when maximal acoustic capacities display a hearing loss of about 30dB, as opposed to normal hearing. Basically, an average level of hearing loss inferior to 40 dB is enough to maintain a perception of the surrounding environement: of course, some useful information will be altered, but to a degree that is sufficient to maintain the capacity to create a coherent mental representation, compatible with a normal social life.

And this is all the more so because the ambient backgroung noise often reaches those levels in daily life: it has a similar effect to an increase in hearing threshold. The onset of acoustics events during the hearing process does not display major variations compared to a normal hearing function. Indeed, the main relevant characteristics of speaking out loud – the average level of which is 60-70 dB HL at proximity to the speaker lips – can be perceived… and a bit of lip reading provides the complementary information. This explains why, nowadays, we still come accross teenagers suffering from a light sensoneurinal hearing loss that is only diagnosed when they get to university, and that remained undetected till then (such cases occur less often than in the past, though, due to a systematic control of hearing function at earlier stages). However, the impairment does exist and results in an incapacity to hear whispering voices, remote sounds or rustles: all of this does cause some inconvenience in social life and restrain the environment. The combination of an additional impairment in the child will have major consequences: the amblyopic patient will lack the complementary information for a proper hearing, a patient with mental disease will suffer from a stronger sensoneurinal impairment, disabled people will have more trouble to structure their environmemnt, etc. It is thus crucial to check the hearing function in all patients suffering from sensory, intellectual or physical disabilities, and to treat any hearing impairment no matter how light it is.

The next level of hearing loss is set at 50 dB, the average level of hearing disabilities. As a result, we distinguish an up-to-50 dB group and a beyond-50 dB group of average hearing impairment. This is the point where most of the acoustic information contained in speech is not accessible to the hearing impaired. Below that average threshold, and in particular if the test shows a better hearing of deep or high-pitched sounds, the relevant sounds that are perceived allow an autoadjustment of the patient’s voice. Indeed, those patients can control their voice, tune, pace, vocal timbre and phonatory production. Above the 50 dB level of hearing loss, some timbres are missed. An absence of high-pitched tones alters the quality of the voice, as if it was timbre-depleted, the movements of the soft palate cannot be controlled properly and the articulation of consonants – those with a high-pitched tone in particular – is not as sharp as normal, it is diminished by as much as what the patient can hear. This 50 dB threshold of average hearing loss will be addressed at a later stage, when the disabling aspects of hearing impairment will be discussed. This is when we get to the world of deafness as the society conceptualises it: the verbal and social impairment, the impact on schooling, the attitude of the hearing impaired…»(1).

JYM

(1) Prof. J.C. LAFON « les enfants déficients auditifs »(« hearing-impaired children ») page 107.
 
 

Como lo escribe el Profesor J.C. LAFON:

« La fecha de aparición de la surdida es fundamental para el futuro del niño

Lo que es adquirido en el momento de la surdida deja como huella la organización neurosensorial inducida por la excitación acústica, así como algunos mecanismos psicofisiológicos en la medida donde otras vías sensoriales permiten la continuidad de su actividad. Así la noción de profundidad del espacio donde el rasgo acústico es importante en la edad de un año, es soportado por la visión de la perspectiva en un condicionamiento remanente: la vista recuerda los signos auditivos y los reemplaza. A lo contrario lo que es a dominante auditivo de manera fundamental como el habla articulado apoyado por el lenguaje verbal es mucho más frágil.

Antes del nacimiento es muy difícil conocer la incidencia de la fecha de la sordera por lo difícil que es determinarla fuera de la rubeola o de una enfermedad evidente. Habitualmente las que intervienen durante enfermedades del feto son tal vez menos profundas que las de los primeros meses. La inducción sobre la estructura de sistema nervioso es probablemente menos importante. En cuanto a un logro memorial, es una imprecisión poética atractiva de la relación madre-feto donde cada uno proyecta su afectividad. No creo que tenga gran importancia en su especificad, tan la memoria que soportaría esta relación es lábil. Se trata mucho más de una elaboración del sistema auditivo que de una psicología relacional específica. 

En el nacimiento la sordera se produce en un sistema del cual los reflejos innatos han sido ampliamente funcionales aunque sus efectos específicos no tuvieron lugar, como es el caso de reflejos elementares. Es así para los reflejos auditivos construidos pero sin su finalidad. Fuera de diferencias autonómicas conocidas estadísticamente, la disminución del perímetro craniano, no se encuentran muchas disparidades en el nivel educativo tanto otros factores influyen sobre el desarrollo de la personalidad, permitiendo a niños con menos posibilidades de ocuparlas mejor.

En la primera edad, antes de un año, nos encontramos frente a los logros psicofisiológicos: relación afectiva lactante más completa, mejor conocimiento del entorno, control de la voz y de las melodías… Todo esto con la condición que los padres sepan hacer perdurar estos logros, lábiles, lo más tiempo posible utilizando las otras vías sensoriales.

A partir de un año, aunque todas las adquisiciones de habla y de lenguaje verbal se borran, tantas informaciones y funciones están memorizados que siempre queda algo, no siempre en el inmediato de las realizaciones más bien en un pronóstico a largo plazo. La puesta de aparato auditivo es eficiente sobre un sistema construido, las posibilidades de simbolización son mejores. Se constata además que los sordos profundos 2do y 3er grupo que van más allá de la escolaridad del bachillerato son con frecuencia sorderas adquiridas de la primera edad, al igual que sorderas profundas del 1er grupo o sorderas severas congeniales.

A la edad de 3 años, una sordera y sus consecuencias educativas son de otra importancia. Si hay logros perfectamente construidos que se vuelven ciertamente menos utilizados, que se borran por parte en sus aspectos los más finos, en cambio la repercusión afectiva y social, la sensación de una pérdida de la personalidad, el aislamiento relacional y afectivo son esenciales en las dificultades encontradas por el niño. Seguramente la puesta de aparato auditivo muchas veces casi inmediata (debería serlo imperativamente) compensa un poco estas dificultades. Pero el sentimiento de frustración injusto sigue muy vivo y pide una asistencia afectiva bien desarrollada, sin sobreprotección ni ruptura, hasta en los detalles de la vida cotidiana. Hemos visto en una sordera urliana bilateral profunda, el niño volverse insomne tanto el hecho de cerrar los ojos le cortaba totalmente del mundo, especialmente de sus padres. Este sentimiento de abandono total se demoró meses a superar. Algunos años más tarde el habla se deterioró considerablemente, el lenguaje ha retrocedido, mucho más si la sordera ha sido más precoz y que la asistencia ortofónica no fue inmediata.

A partir de 5 años, el problema específico es el aprendizaje de la lectura. Hay que establecer los más pronto posible sobre signos escritos lo que hasta ahora es solo oral para conservarle rasgos pertinentes complementares a la fijación memorial. A esta edad el lenguaje es suficientemente desarrollado para que el efecto de la sordera no cuestione el nivel de simbolismo y de abstracción alcanzado por el niño. El habla pide a lo contrario una vigilancia ortofónico precisa, los automatismos, aunque bien establecidos, solo tienen la audición para ser controlados.

Después de 8 años, estamos casi delante de una sordera adquirida del adulto siempre que la asistencia educativa permite sin demasiados problemas el mantenimiento en un curso escolar normal en su desarrollo y naturalmente el mantenimiento en el ambiente social y afectivo anterior. » (1).

JYM

(1) Pr. J.C. LAFON « los niños deficientes auditivos » páginas 106 – 107.

To quote Prof. J.C. LAFON:

« The exact timing of the onset of deafness is crucial for the future of the child.

What is already assimilated when deafness arises remains both as a neurosensory organisation triggered by an acoustic excitation, and as some psychophysiological mechanisms, provided that other sensory pathways allow their continuation. For instance, the notion of depth – in which the acoustic aspect plays an important role in one year old-toddlers – is switched to the visual perception of perspective as part of a residual conditioned behaviour: the sight both recollects auditory signals and replaces them. However, perceptions that rely mostly and inherently on auditory signals – such as articulated speech supported by verbal speech – are much more fragile.

Prior birth, one can hardly assess the consequences of the timing of the onset of deafness, as determining this moment is complicated – except in case of rubella or other obvious diseases. In general, deafness caused by illnesses during the foetal life are not as severe as those occurring during the first few months after birth; its consequences on the neural system structure do not seem too severe. As for a so-called ‘gained memory’, this is just another fantasy about the mother-foetus relationship, in which everyone tend to project their own affectivity. I do not think it could be of major importance, on a specificity point of view, as the memory function that would be involved in this relationship is very unstable. This is more about the elaboration of the auditory system rather than a particular psychological relationship. 

At birth, deafness affects a system whose innate reflexes have been in operation for a while although their specific effects did not have time to develop, just like elementary reflexes. It is the case of developed auditory reflexes that did not have time to achieve their final purpose. Beside anatomical differences found specifically in those children, based on statistical analysis – e.g. a decrease in skull circumference – no major differences have been found on an educational point of view: indeed, numerous other factors impact the development of a child’s personality and allow those with less capabilities to make a better use of them.

Before one year old, babies display acquired psychophysiological mechanisms, i.e. the new-born shows a more advanced affective relationship, a better understanding of its surrounding, a control of the voice and tunes… All this, provided that the parents manage to maintain these acquired but fragile mechanisms through the stimulation of other sensory pathways.

From one year old, although the major speech and verbal language capacities tend to disappear, so many functions and information have been acquired that there will always be some left: not necessarily immediately after they occurred, but rather in the long term. Hearing devices are efficient on a developed system, with better symbolisation capacities. Indeed, reports show that group 2 and group 3 severely death students who pursue their studies beyond A-levels are often suffering from a deafness that developed during the earliest age, just as group 1 severe deafness or severe, congenital deafness.

At the age of three, deafness and its educational consequences have a different, stronger impact. Some acquired mechanisms that are perfectly developed tend to be employed less often, the most elaborated parts of which even tend to disappear. The social and affective consequences of deafness, such as a feeling of losing their personalities and a social and affective isolation play a key role in the issues children are facing at this stage. Wearing hearing devices -equipment is usually provided almost immediately (and should be in all cases), does compensate some of these issues. However, very strong feelings of unfairness and frustration remain and do require a targeted management of the child’s emotions – without being overprotective nor causing a rupture – down to all aspects of everyday life. In a reported case of severe, bilateral, rubella deafness, closing the eyes at night was so isolating from the surrounding world – and from the parents in particular – that the affected child also suffered from sleeplessness. It took months to overcome this feeling of complete abandon and isolation. Within a few years, considerable speech deterioration and language regression were observed, all the more so as the onset of deafness occurred at an early stage and that speech therapy was not initiated immediately.

From five years old, the major issue is learning how to read. What remains of oral signals must be associated with written signs as soon as possible in order to maintain relevant mechanisms of memory fixation. At that age, the language development is at a sufficiently advanced stage to ensure that deafness will not jeopardise the child’s level of abstraction and symbolism. Speech, on the other hand, requires a thorough management, as the control of the automatic – and well established – mechanisms involved does rely on hearing.

From eight years old, deafness is almost similar to acquired deafness in adults, provided that the educational management allows the continuation of a regular curriculum in the same social and affective environments as before »(1).

JYM

(1) Prof. J.C. LAFON « hearing-impaired children » pp. 106-107.

Nous sommes fin mai 1994. Je suis tout heureux car j’ai réussi à obtenir du Professeur Jean-Claude LAFON qu’il intervienne durant deux jours au siège parisien de l’entreprise pour laquelle je travaille. Une petite dizaine d’Audioprothésistes est là pour l’écouter. J’enregistre ses paroles sur cassettes à bande magnétique. Ce que je vous propose en est une retranscription écrite, non in extenso car malheureusement certaines cassettes s’avéreront de mauvaise qualité et donc inaudibles à l’écoute. Je m’en veux encore !

Professeur Jean-Claude LAFON :

« Avec Paul VEIT nous avons choisi 3 mots « paille, rive, cil ». On étudie ce qui sort d’une prothèse. Sur le plan de la discrimination l’écart entre 2000 et 3000 est beaucoup plus important qu’entre 5000 et 6000. Alors on a utilisé une échelle pseudo-logarithmique partant de 1500 avec une compression progressive des aigus et une compression progressive des graves. Les sons très graves et très aigus étant très peu signifiants. On a divisé le sonagramme en tranches de 30 millisecondes et on a choisi des niveaux de noirs qui correspondent aux noirs du sonagramme. On a une représentation quadrillée par « unité de valeur », à partir de 3000 Hz on a une compression de la zone aiguë et à partir de 1500 une compression de 500 par rapport au 1000. Cela donne un calcul échantillonné de l’ensemble.

Densité spectrale instantanée : on a fait la somme de ce que donne la prothèse par rapport à ce que donne le signal normal.

Tout ceci montre qu’avec un sonagramme on peut arriver aussi à voir certaines qualités des prothèses : l’analyse au sonagraphe de la sortie des prothèses est intéressante parce qu’on voit (comme avec l’étude phonétique de l’intelligibilité) apparaître des choses pas normales (bruits, répartition temporelle erronée…) qui donne bien une indication de qualité.

On a donc deux possibilités dans l’étude des prothèses : l’étude phonétique et une étude d’analyse acoustique de la sortie des prothèses qui est vraiment très intéressante »

JYM

Nous sommes fin mai 1994. Je suis tout heureux car j’ai réussi à obtenir du Professeur Jean-Claude LAFON qu’il intervienne durant deux jours au siège parisien de l’entreprise pour laquelle je travaille. Une petite dizaine d’Audioprothésistes est là pour l’écouter. J’enregistre ses paroles sur cassettes à bande magnétique. Ce que je vous propose en est une retranscription écrite, non in extenso car malheureusement certaines cassettes s’avéreront de mauvaise qualité et donc inaudibles à l’écoute. Je m’en veux encore !

Professeur Jean-Claude LAFON :

« A 5 sujets normo-entendants A B C D E on passe les listes 10 11 12 13 14 des listes cochléaires dans deux conditions : on enregistre le son qui sort de la prothèse sur une bande magnétophone. En même temps on enregistre une sur la seconde bande de la piste les listes en direct. On a deux enregistrements qui ont le même problème (même bande) sur le plan du magnétophone. On étudie la discrimination en direct et à travers le prothèse. Pour A c’est au total des 5 listes 36erreurs/56erreurs, B 33/51, C 50/63, D 38/71, E 29/41, E 29/41. A+B+C+D+E 186/287 (pour la liste 10 A+B+C+D+E 31/50, liste 11 55/77, liste 12 35/62, liste 13 28/47, liste 14 37/41). On a passé la bande à des niveaux qui sont juste à la limite de la courbe d’intensité. Les deux enregistrements sont passés au même niveau pour une personne donnée. La moyenne avec la bande mère est de 7.44 erreurs par liste (écart type de 0.55). Avec la prothèse elle est de 11.28 erreurs par liste (écart type 0.82). On peut essayer ainsi plusieurs prothèses et voir la différence de qualité phonétique entre les prothèses. On a ainsi la quantité d’information phonétique transmise. C’est plus précis que n’importe quel essai clinique. Ce n’est utilisable que sur des prothèses qui sont considérées comme utilisant l’ensemble du champ auditif. Je regrette que les fabricants ne l’utilisent pas car ils verraient qu’il y a des prothèses ou des réglages de prothèses qui ne sont vraiment pas bons »

JYM