18. Notes on the Anatomy and the Physiology of the Ear¹⁰⁹

The ear is made up of three distinct parts: 1. The outer ear, consist­ing of a lobe or pinna, the external auditory meatus, and the tympanic mem­brane (ear drum); 2. The middle ear with a chain of ossicles (little bones), muscles and ligaments, and the Eustachian tube; and 3. The inner or internal ear with the cochlea, the vestibule, and the semi-circular canals.

The Outer Ear110

The entire external ear is shaped like a shell and called the concha. Its function is to collect the sound waves and reflect them into the meatus. The lobe or pinna is valuable in intensifying the sounds and also in determin­ing their direction.

The canal of the external ear is not straight. It extends backward and upward, and then turns inward to the tympanic membrane (ear drum). All sounds that affect the ear pass through this canal.

The tympanic membrane consists of three parts: a layer of skin which forms the outer coat; a layer of mucous membrane which forms the inner coat; and a layer of fibrous connective material which lies between the inner and outer coats.   The membrane has the shape of a shallow funnel.

The Middle Ear111

The middle ear is made up of a small chamber called the tympanic cavity, which contains a chain of three movable bones, the tympanic antrum, and the Eustachian auditory tube. The small chamber, the tympanic cavity, lies in the temporal bone, one of the bones of the skull, and is filled with air. It is closed at the outer end by the ear drum or tympanic membrane, which is a little more than a quarter of an inch wide. Vibrations of the ear­drum are transmitted across the middle ear by the chain of ossicles (little bones) joined together across the tympanic cavity. The chain consists of a malleus or hammer, which is attached to the inner side of the ear-drum, the incus or anvil, and the stapes or stirrup which complete the chain. The three bones resemble objects for which they are named.

By means of the Eustachian tubes, which run on each side of the naso­pharynx backwards and upwards to the middle ear, the air in the middle ear is kept under the same pressure as the outside air.

Five ligaments connect the auditory bones (ossicles) to the walls of the ear-drum membrane. Three of these are attached to the' malleus (mallet) , a fourth connects the short process of the incus (anvil) to the posterior wall of the ear-drum, and the fifth connects the base of the stapes (stirrup) to the circumference of the oval window. This is an opening in the medial wall of the tympanic cavity, into which the footplate of the stapes (stirrup) is in­serted. The incus (anvil) lies between the articulates with the other two ossicles.

Another opening into the middle ear is the round window, which is cov­ered by the so-called secondary tympanic membrane.

The tympanic cavity contains two muscles: the tensor tympani and the stapedius. The tensor tympani is attached to the handle of the malleus, and when it contracts it pulls the handle of the malleus inward, thereby prevent­ing excessive outward displacement of the ear-drum. The stapedius (stirrup) muscle is attached to the posterior surface of the neck of the stirrup. When it contracts, it pulls the head of the stirrup backwards, thus tilting the an­terior edge of its base towards the tympanico cavity, and reducing the pres­sure on the oval window.

The Inner Ear 112

The inner ear or labyrith contains the receptors of hearing. It is made up of three parts: the vestibule, the semi-circular canals, and the cochlea. In the lateral wall of the vestibule is the fenestra vestibule (oval window) , through which sound vibrations are transmitted from the middle ear to the inner ear. The organs of equilibrium are the semi-circular canals which have no auditory function. The organ of hearing, the cochlea, so named from its resemblance to a snail shell, is a spiral shaped tube of two and three quarter turns, about a quarter of an inch in diameter at its base. It is located just inward from the middle ear and below the semi-circular canals.

The spiral tube or canal of the cochlea winds around a central axis called the modiolus, which divides the cochlea into two separate spiral canals. The division is completed below by the basilar membrane, and above it by the vestibular membrane. The spiral canal between the two membranes is called the cochlear duct, within which the sensory cells of hearing are lo­cated. The duct is filled with a fluid called endolymph. The part lying above the membranous tube is called the scala vestibule - scala: resembling a stairway - and the part lying below is called the scala tympani. Both are filled with a liquid called perilymph. The scala vestibule is connected to the middle ear by the oval window; the scala tympani to the middle ear by the round window. The two windows, covered with flexible membranes, provide the otherwise rigid walls of the cochlea with flexible walls, which permit movement of the sound vibrations through the medium of the liquids in the cochlea.

Sound vibrations from the tympanic membrane (ear-drum) are trans­mitted across the middle ear by the auditory ossicles - the mallet, the anvil, and the stirrup - to the oval window. The vibrations cause the oval window to move inward and outward, setting up vibratory movements of the peri­lymph and endolymph liquids in the spiral canals of the cochlea, along with an outward and inward movement of the round window. As a result, the basilar membrane is set into sympathetic vibration.

The nerve of hearing, the auditory or cochlear nerve, enters the cochlea at the base of the modiolus or central axis. Its fibers, winding upward and piercing through the axis all along the spiral turns, terminate in the basilar membrane. Resting on the basilar membrane is the organ of Corti, a mass of nerve cells which act as the auditory receptors of the sound vibrations. The cells are made up of what are called inner and outer rods and hair cells. The hair cells have hair-like projections, approximately twenty-four thous­and in number. Between the cells are the delicate ending of the auditory nerve. Movement of the fibers of the basilar membrane through the peri-lymph liquid sets up vibrations in the hair cells. This action stimulates the endings of the auditory nerve in the organ of Corti, and what originally were sound waves now become nerve impulses which are carried to the brain.

Hearing113

Hearing, a psycho-physiological response, is considered to be a spec­ialized form of the sense of touch, the inner ear having developed from a primitive tactile organ.   Hearing is a pre-condition of speech.

The normal ear has an enormous capacity to interpret and analyze sounds. It is sensitive to vibrations lying with a certain range of frequen­cies, the average for normal individuals being between 20 to 20,000 vibra­tions per second, approximately 10 octaves. It is very sensitive to small changes in the pitch of successive tones, except toward the upper and lower limits of hearing. Discrimination is acute in the middle range, and many musicians develop absolute (perfect) pitch, a memory for tones in the middle range. It is not as sensitive to changes in intensity as it is to changes in pitch. Toward the extremes of the pitch range, discrimination and memory become more difficult.

Nearly all the speech sounds by which we are able to understand words have high frequency regions. According to the Bell Laboratories, if all the frequencies above 500 are eliminated, only five percent of the words will be understood. In the matter of loudness, there are definite limits to the sen­sitivity of our ears. In other words, there are sounds that will be too soft to be heard, and sounds that will be too loud and felt instead of heard. Be­tween these two extremes, which are termed the threshold of audibility, and the threshold of feeling, there is a wide range of variation for different sounds and for different ears.

Hearing Tests114

Tests can be made of an individual's hearing by means of an audiometer (decibel meter), an instrument that measures one's ability to hear minimum intensities at different pitch levels. These can be charted on what is called an audiogram. The analysis is represented in terms of decibels, a unit by which the loudness of a sound can be measured. A decibel is one tenth of a bel, a unit of intensity, named in honor of Alexander Graham Bell, the in­ventor of the telephone.

In measuring the loudness-difference between two sounds, loudness de­pends not on the difference in intensities involved but on their ratio. This is based on the Weber Fechner law, which states that equal increments of sensation are associated with equal ratios, or equal increments of the loga­rithm of the stimulus.

In other words our ears respond logarithmically to the physical energy in a sound wave.   When one sound wave has ten times the physical intensity of another, the logarithm of the intensity ratio is 1, and the first sound is said to be 1 bel above the second. When one sound has a 100 times the phy­sical intensity of another sound, the logarithm of the intensity is 2, and it is said to be 2 bels or 20 decibels above the second sound. Since the decibel deals in ratios, small differences in decibels represent great differences in intensities.

By means of the audiometer, the amount of any hearing loss can be de­termined. Deafness is usually not uniform over the entire pitch range. A person may be deaf to pitches in a certain range - called islands of deafness - but be able to hear normally in the rest of the range. Correction of this loss can be made in many instances by the use of a properly fitted hearing aid. This makes it possible for many persons who have a hearing loss to participate in musical activities, and from the standpoint of speech pathology, it is advisable that they do so in order to maintain what hearing they do have by hearing activity.

Early Theories of Hearing116

The resonance or harp theory advanced by Helmholtz compares the twenty four thousand or so fibers that makeup the basilar membrane as being tuned, somewhat like the strings of a piano or harp, to different frequencies. The fibers vibrate according to the principles of sympathetic resonance at dif­ferent levels of the cochlea. The vibrations set up impulses in the nerve ends in the hair cells at those particular places. The stimulated places are recognized by the brain as differences in pitch. The short transverse fibers at the base of the cochlea resonate to high pitches; the longer fibers near the apex resonate to lower pitches. The basilar membrane represents the piano sounding board and its many strings, and vibrates selectively. Analysis of the sounds is said to occur in the cochlea.

The telephone theory117 as advanced by Rutherford and later by Wrightson, compares the basilar membrane to the diaphragm of a telephone. In a tele­phone system, sound waves, which have been converted into electrical im­pulses of the same frequency, travel to the receiver. Here the electrical impulses set up vibrations which are reproduced as the original sound. In hearing, the frequencies of the sound waves are carried to the basilar mem­brane, where they are converted into nerve impulses and carried to the brain for analysis. According to the telephone theory, the basilar membrane vib­rates as a whole, and not selectively as in the harp or resonance theory.

The displacement theory1 as advanced by Max F. Meyer considers the basilar membrane as an indifferent mass. According to this theory, sound waves from the middle ear set up pressure impulses on the liquids in the cochlea. The basilar membrane gives way to these pressures, allowing for the displacement of the round window (fenestra cochlea), and the movement of the liquids in the cochlea. For a sound wave of 256 vibrations per second received by the ear, the fluids in the cochlea vibrate at the same rate, 256 v.p.s. In turn, the nerve endings in the spiral organ of Corti on the basilar membrane vibrate at 256 v.p.s.   Intensity is dependent on a greater movement of stapes (stirrup) in the middle ear which activates the oval window (fenestra vestibuli) and the fluids in cochlea, resulting in a greater move­ment of the basilar membrane. According to this theory, any nerve can carry all pitches, and greater intensity is dependent on more nerve fibers being stimulated.

The Ewald theory considers the basilar membrane as an elastic surface, parts of which become nodal depending on the complexity of the sound wave pattern.   This allows for cochlear analysis of sound.

A present day theory of hearing is the piezo electric effect120 According to this theory, movements of the basilar membrane produce push and pull movements on the hair cells in the organ of Corti. This results in a change of the mechanical energy in the sound waves directly into electrical energy. This has been termed the microphonic action of the cochlea.

Theories of hearing are based on a cochlear analysis of sounds, or on an analysis in the cerebral cortex, or on both. The harp or resonance theory is the most widely accepted, and is based on cochlear analysis.

Methods of Hearing 121

There are two methods of hearing. We hear others through air conduc­tion; we hear ourselves through air and bone conduction. Needless to say, we do not hear ourselves as others hear us, which makes it doubly difficult for a student to judge his own efforts. It makes the choice of the right teach­er tremendously important, since he, the teacher, must be able to direct the student correctly until the student is able to judge his own singing ob­jectively.

SONG TRANSCRIPTIONS

Explanation the "Square" Position

The "square" position of the lips is a means to an end, which is to eliminate the use of the lips in the pronunciation of the vowel sounds, par­ticularly the vowel sounds of oh and oo.

This results in establishing vowel sets or shapes in the back of the mouth, to include the back and base of the tongue, the pharynx, and the soft palate. The production of the vowel sounds in the back of the mouth has been termed "pharynx enunciation."

The square position (or bell-like or open puckered position) has the effect of a small megaphone, in keeping the sounds from dissipating. It also establishes the tactile sensation of the tone being forward. This in turn makes for great flexibility, not only of the pharynx, but also of the articulators - the tongue, the lips, the soft palate, and the lower jaw.

The square position therefore is not to bethought of as a fixed or rigid position of the lips, but essentially a flexible position which allows for the shaping or pronouncing of the vowel sounds by the lips when necessary. Examples:   Soft singing, German umlaut vowels and French lip vowels.

Summary

The basic theories presented for the training of the singing voice apply to child, adolescent, teenager and adult, and to both male and female.

There are, however, fundamental differences involved. For example, in the teaching of children there must be a limited amount of explanation of how the mechanism works. The teacher must depend almost entirely on the use of imagery. Also, young girls voices and boys unchanged voices work essentially the same way as do older female voices. There is com­paratively little vibrato in the younger group before puberty. Although the teaching of vocal techniques has been frowned upon generally by school authorities and teachers of singing, children can be taught basic funda­mentals which will protect their voices against incorrect singing and yelling at athletic events.

The great difference in the teaching approach to older male and female students is the problem of how much to explain. Generally speaking, female singers and female teachers of singing are not particularly interested in the scientific aspects of how the vocal mechanism works. Male singers, on the other hand, usually want to know how and why.

The best approach to either group is to teach them how first without explanation. If the teacher is successful in his teaching, little needs to be explained. Lack of success may be the result of lack of understanding. In any case the teacher should fit his explanations to the students type of mind.

A particular difference in mental attitude between male and female students is in the problem of registration. Most young female singers have comparatively little difficulty in vocalizing a three octave range - two octaves above the average pitch of the normal speaking voice, and one octave below, using an open ah vowel sound in an open square position of the lips. The registration changes occur naturally if the singer doesn't interfere. The average female singer is convinced that a knowledge of how or where the changes in registration occur will tend to make her conscious of these changes and interfere with a natural change.

In male voices, however, there is a definite limitation in the natural singing range to about an octave and a fourth or fifth above the average pitch of the normal speaking voice, and in some cases a range of several notes below. An extension of a third or fourth or more above the octave and a fourth or fifth is dependent on learning how to sing in the high voice mechanism. This is a matter of learning how to change the falsetto regis­ter into what sounds like a continuation of the middle voice. This change does not come naturally, but must be taught.

Women teachers of singing find the teaching of the male high voice a difficult problem. This is undoubtedly due to the fact that there is no com­parable falsetto register in the female voice.

One of the problems in developing registration in male voices is to make smooth transitions from one register to another, particularly from the middle to the high voice, so that the register changes are not notice­able. Many singers and teachers are mislead by this smoothness, par­ticularly in the singing of artists, into believing that there are no registers in the singing voice.

There is also a difference in the breathing for singing between female and male singers. Female singers breathe higher, that is, more inter-costally than male singers, who use a combination of intercostal and high abdominal breathing on both inhalation and exhalation. There should be no basic difference in actual breathing for singing between the two sexes. The female singer needs to be taught a stronger, high abdominal support.

Clear diction, particularly in the high voice, is also more of a problem with female singers than with male singers. The clearest diction in the female voice occurs in the lower ranges. The high voice diction is defi­nitely limited in its understandability. This can be explained in part by the fact that female voices lie an octave higher in the sound spectrum than male voices. In this higher pitch range there is a narrower band of possible vowel sounds which must be modified, thereby limiting the intelligibility of the words. Above high C in the coloratura register, the modification limits the singer to one neutral sound, a modification of the vowel sound ah.

A final question may well be asked:

When can singing lessons be started?

A training of the singing voice - to include both girls and boys - can be begun at about ten years of age, about fifth or sixth grade.

Four basic fundamentals can and should be taught:

1. Normal quality
2. A singing diction
3. How to sing in the high and low voice
4. How to breathe for singing
   

Children should be taught in classes. They should be taught by teach­ers who know how to teach the four basic fundamentals.

It is questionable whether children - both boys and girls - should be taught during puberty changes. These changes occur in girls around twelve and thirteen years old. During this time the female voice is breathy, and lacking in intensity. The puberty changes in boys voices are evidenced by a lowering of the voice about an octave in range. Most teachers of singing advocate resting the voice during this period until the changes are complete.

The same basic fundamentals learned as a child can be carried over into the training of the singing and speaking voice after the puberty changes.

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