The Ear and Sound
THE HUMAN EAR
The Tomatis Method® is above all a pedagogy (education) of active listening;
its goal is to give everyone the desire and the possibility to use his
or her auditive function to its full potential and thus to enter into
a real dynamic of communication.
However, in order to better understand the mechanisms, notably the psychological
mechanisms, which can lead to dysfunction in communication, it is necessary
to know how the human ear functions.
- The ear is formed of the outer part (auricle, outer
auditory canal, tympanic membrane), the middle part
(tympanic cavity, ossicles composed of the hammer, anvil and stirrup
bone) and finally the inner ear (the labyrinth, composed
of the vestibule and the cochlea).
- The outer ear and the middle ear function in the air
environment, whereas the inner ear functions in the liquid
- Each part of the ear participates in the perception of sound. The
purpose of this particular function is hearing, and its functioning
can be impeded not only by mechanical causes, but also by psychological
causes affecting the desire to listen to a greater or lesser degree.
- The development of the listening function will condition a particular
triad represented by verticality, laterality
- Correctly speaking, the sensorial organ is the membranous labyrinth,
composed of the vestibule and the cochlea.
- The vestibular part manages the balance of the body
thanks to the utricle and the semicircular canals which also bring temporal
and spatial awareness; thanks to the saccule, the vestibule also manages
the awareness of body image. The two vestibules work
- The cochlear part assures both the differentiation of sounds and the
cortical charge; this cerebral stimulation contributes to the
constant evolution of the field of consciousness.
- These two functions enable one to have a perception of the external
and internal worlds which is constantly deepened, through sequential
analysis on the one hand, and a quantitative analysis of frequency on
- The membranous labyrinth appears first in the development of the foetus;
followed by the bone labyrinth, the middle ear, then the outer ear as
protection, regulation and perfection of the system. The entirety of
the auditory sensorial organ is constituted at four and a half months.
- On a cellular level, the auditory cell is a aquatic ciliary cell,
like the first sensorial cell; from the outset it plays the role of
a stimulation sensor and both carries information and transforms these
stimulations into electrical energy, thus participating in the activity
of the brain and therefore in the vitality of the organism. Moreover,
these cells give the first information on the surrounding space.
- It circulates in an elastic environment in which the possibility
of extension exists.
- It results from vibratory movements represented in physics by a sinusoid
- Its wavelength characterises the frequency in Hertz (Hz): the shorter
it is, the higher the frequency.
- Its intensity is expressed in decibels (dB): it is dependent on the
amplitude of its wavelength and therefore on vibratory movement.
- Its speed is all the greater in that the environment in which it develops
becomes more dense, 330 m/s per sec in air, 1500 m/s in water and 5600
m/s in glass, respectively.
- It is directly related to the phenomenon of acoustic resonance; in
fact, through the emission of a particular note, any object which creates
this note is itself set in movement (e.g., a singer can make a glass
"sing" and if the sound intensity surpasses the resistance
of the glass, the glass will break).
- It is naturally complex: it contains a more or less basic low note
which will contain and generate a whole range of more high-pitched harmonics.
- To be pure, it must be created by a sophisticated technology; a classic
audiogram in an anechoic room therefore does not really translate the
usual auditory attitude.
Sound and the Ear
- The human ear has an auditory spectrum ranging from 16 to 16,000
Hz; below this auditory spectrum lies infrasound and beyond, ultrasound.
- The whispered voice is situated at 25 dB, the spoken voice at 60 dB,
a rock band at 90 dB. The ear is in danger if it is exposed to 100 dB
for a long period of time, the pain threshold is reached at 120 dB and
a threshold of very serious danger is situated at 150 dB.
- The discriminative ability of the ear allows for the fine analysis
of sounds, this function going progressively from low-pitched to high-pitched
sounds during childhood.
- Solicited by several sounds, the ear can "choose", both
voluntarily or non voluntarily, the sound which it wishes to focus on;
in the case of automatic selection, it is not rare to see a psychological
dimension appear, the subject blocking out the perception of certain
frequencies over others.
- The ear can focus on several sounds at once, provided that one of
them is not clearly dominant, as a sound of strong intensity covers
the totality of the sound environment through auditory saturation: this
is the mask effect.
- Bone conduction is favoured in relation to the air and aquatic environment;
it is transmitted to the soft tissue and to liquids with a slight latency
time. The transformation of sound from air to bone takes place through
the tympanic membrane.
- The ear has a complex system for the regulation of
sound information: it is first of all pneumatic through
the variation between the air pressures of the outer ear and the middle
ear, neurological through the action of the glossopharyngeal
nerve controlling the opening and closing of the Eustachian tube, mechanical
through the mobilisation of the musculo-ligamental-ossicular apparatus
of the outer ear and above all of the middle ear (the ossicles and the
muscles of the hammer and the stirrup simultaneously playing on the
tympanic membrane and on the oval window), liquid,
finally, in the inner ear through the apparition of turbulence in the
perilymph and the endolymph which shakes the basilar membrane where
the sensorial cells are implanted.
- It should be noted that three constant features are
necessary for the correct functioning of the inner ear: regular temperature,
good vascularisation, and normal physiological pressure.
- The ear plays the role of a dynamo, participating
very significantly in the charge of the cortex; in this function, high-pitch
frequencies are very important, to the extent that they correspond to
very dense iso-frequency zones in sensorial cells and are all the more
stimulated when the sound is intense.
- Listening, contrary to hearing, is a willed act expressing a real
desire and making the whole body participate; as a result, one can easily
appreciate the psychological dimension of The Tomatis Method® which
is very much a pedagogy (education) of listening and the very particular
attention paid to working on the listening posture.
The Propagation of Sound
- Several theories on the propagation of sound exist, and notably that
of Helmholtz, developed by Bekesy, and that of A. Tomatis corroborated
by the results obtained thanks to his Method of listening education.
- Bekesy's classic theory stipulates that sound passes
through the ossicles, from the tympanum to the oval window, inducing
the appearance of turbulence in the perilymph and the endolymph which
shakes the basilar membrane where the sensorial cells are implanted;
the cilia of these cells immobilised by the tectorial membrane are then
activated in terms of a polarisation or a depolarisation which is expressed
by a nervous stimulus. The round window is mobilised by the turbulence.
- Tomatis's new theory stipulates that sound arrives
to the tympanum, is transmitted to the sulcus tympanum, to the petrous
pyramid, the bone labyrinth, the spiral ganglion and the membranous
labyrinth. The tectorial membrane mobilises in relation to the basilar
membrane, stimulating the cilia of the sensorial cells. The endolymph
is set in movement: formation of endolymphatic, then perilymphatic turbulence
occurs, the latter coming into collision with the round window and the
- The outer ear has the same function in the two theories: the form
of the auricle allows, through its specificity, on the one hand to apprehend
certain pieces of information concerning the surrounding space and on
the other, to give maximum focus to the sound wave which is then canalised
by the external auditory meatus to be concentrated on the tympani. This
action is increased by the tension of the auricular muscles, associated
by a particular listening mimic of the muscles of the face and the cranium.
- The middle ear plays the role of transmitter in the classic theory
and of regulator-damper in the new theory.
- The inner ear is not stimulated in the same way in the two theories:
in the classic theory, there are propagation fibres in the basilar membrane
which the sound wave stimulates through liquid propagation (this is
Bekesy's turbulence). In the new theory, there is neither liquid propagation
of the initial sound wave, nor propagation of the basilar membrane:
in fact, on the one hand, air conduction becomes bone conduction as
soon as it reaches the tympanum, and on the other hand, the existence
of iso-frequency zones in the cochlea allows for a spontaneous analysis
in relation to frequency and intensity.