Overcoming Deafness

The Story of Hearing and Language

Ellis Douek

• Publisher: ICP
• Year: 2014
• ISBN:
  9781783264674
• Topic: Medicine
• Subtopic: Pediatric Medicine

Hearing is one of the most empowering of our senses; it enables us to work, socialise and communicate. It's hard to imagine living in a silent world, yet just 60 years ago this was the inevitable outcome for the majority of people with ear disease or language problems. Nowadays, virtually everybody can be helped to some extent and many cured. But how did we get here?

This book tells the fascinating story of science and medicine's winning battle with deafness, covering all the hearing diseases and the progress of their treatment from the beginning of Ellis Douek's career in the 1950s to the present day. Unlike other books on hearing, this covers language disorders as well as the surgery of deafness; it is a book about human communication, discussing music and poetry as well as delving into the medical science.

In our ageing population, hearing disorders are increasingly a part of everyday life; that they are almost always treatable should not be taken for granted. This book should be the first reference for anyone who has experienced hearing loss and would like to know more about hearing and language development, and for professionals in hearing science, medicine and allied fields of interest.

Contents:

• Sound and Hearing:
  • Sound
  • Hearing
• Deafness:
  • Conductive Deafness
  • Disease of the Middle Ear
  • Perceptive or Neurosensory Deafness
• Communication:
  • Language
  • Music and the Sound of Feelings
  • Poetry and the Sound of Words
• Impaired Communication:
  • When Hearing is Impaired
  • When the Hearing is Normal

Readership: Professionals dealing with communication disorders and hearing science including Surgeons, Paediatricians, Audiologists, Doctors, Therapists and Teachers.

Part I

Sound and Hearing

The sense of hearing allows us to perceive sound, contributing to our awareness of the environment, and to make use of it as a means of communication. We will describe what sound actually is and then what hearing is, the mechanism we have which makes us aware of sound.

Ancient records suggest that people have always thought a good deal about the nature of perception. Despite a lack of experimentation, it was generally understood that perception was associated with the identification of information about the environment. These physiological tools were categorized as five senses: sight, hearing, taste, smell and touch, and Aristotle discussed this process and its interpretation in De Anima (Book II).

There are other types of data both internal and external, such as balance and proprioception, that are anatomically bound up with the sense of hearing and I have described them here. However, the way that the brain handles them is still problematic and Buddhists have long considered there to be another sense, that of the “mind”, ayatana, manifested in the act of “mindfulness”.

Western culture has kept the possibility of a sixth sense open and experiments bordering on science fiction have shown that implanted devices can allow the brain to “see” infra-red light. This means that there is no reason why any form of physical energy, including magnetc fields and radio waves, cannot one day be perceived though a brain implant. In theory, at least, we should ba able to hear high frequencies and even ultrasound in the same way.

For the moment we are limited to the sense of hearing which invloves sensory cells that respond to vibrations of a particular range and their neural connections.

Chapter 1

Sound

Sound is the result of the oscillation of particles such as air. The frequency at which they vibrate decides if the outcome is sound. We have to know how to measure sound to understand it. Its two familiar aspects, loudness and pitch, can be measured relatively easily.

When I was a child we lived on an island in the middle of the River Nile where it flowed through the city of Cairo, separating the more urban side from its still somewhat agricultural districts which soon turned brusquely into desert. The island was considered particularly salubrious as the light breeze that followed the river was broken by our little land mass, creating a turbulence which, though slight by most standards, cooled the air in the heat of the day.

Our island was criss-crossed by wide, leafy streets and when we walked to school some tracts were still in cultivation. We wandered along irrigation channels and, faced with flat, tranquil water we felt a desire to shatter its stillness by throwing in pebbles to watch the ripples which formed around the point of impact.

We watched the little stones strike the placid surface giving rise to a circular wave that travelled outwards in all directions, forming what looked like a series of concentric rings.

The wave did indeed “travel” but in reality it was actually a movement back and forth of water particles creating alternating areas where they are compressed together followed by others of rarefaction as each particle nudges its neighbour then moves back. The wave that results from the movement travels away from the source, forming ripples, and gradually fades away as it loses its initial energy, getting weaker and weaker until it is hardly perceptible.

Apart from their strength or weakness, all waves have another characteristic, their length, which depends on the rapidity of the vibrations. A rather narrow band of wave-lengths, which lies between 20 and 20,000 to and fro movements or vibratory cycles per second, is rather special as we can hear them. Indeed, when particles of air vibrating within that particular range impinge on the eardrum, a thin taut membrane, it will follow their motion back and forth and give rise to the sensation of hearing. It is the vibrations that fall within those limits and which we can hear that we call sound.

The ear is not able to respond to vibrations that are much faster than 20,000, such as some we use in medical scans, so we cannot hear them and we call them ultrasound.

Vibrations that are slower than that range cannot be heard either, as they also have no effect on the ear but we can sometimes feel them and people have complained that low frequency vibrations from machinery have made them nauseous or ill. These slow vibrations are called infrasound.

Not everybody can perceive the whole range of sound frequencies equally well and as we grow older we lose the capacity to hear the faster vibrations. People over 60 years old rarely hear vibrations as fast as 10,000 vibrations per second and as we age further, our range becomes even more restricted at higher frequencies.

Sound vibrations may begin with a lot of strength or energy and we can hear them well as they set our eardrums in motion so we say they are loud. Eventually their energy reduces and the vibrations fade away until they become inaudible. An enormous amount of energy, like that produced by an explosion or even some disco loudspeakers, can be extremely loud and may even cause pain and damage the ear. This dangerous level of power is about ten times that of the minimum audible level.

As well as loudness, which depends on how strong they are, the vibrations have a different effect on our perception according to how rapidly the particles oscillate. Vibrations at a rate or frequency of 1,000 per second have a different effect from those at 250 per second. We hear a different sounds and say they have a different pitch.

If we strike a piano key it will make the string vibrate and in turn this will set in motion the particles of air around it and we will hear the sound when our eardrum vibrates with it. However, unlike the pebble in the water, the string continues to vibrate so long as it has enough energy so that the particles of air keep on oscillating at the same frequency as the string. The sound wave is not now a single event like the ripple in the water, which travels onwards but eventually fades away, but it is a continuous wave always maintaining the same rate of cycles per second.

The wave’s frequency of oscillation remains the same and therefore its pitch does not alter. However, its loudness, which depends on energy that dissipates, gets weaker and the sound we hear becomes fainter. As the source of the sound, the vibrating string, repeats its disturbance of the particles of air at regular intervals with a definite frequency, the wave that results is called a harmonic wave, and the frequency is defined as the number of such disturbances or cycles per second. This regularity also means that the distance between similar points on the wave is repeated exactly and it is known as the wavelength.

Obviously the pitch, frequency and wavelength of the vibrations are closely related, and represent different aspects of the same thing.

One other aspect about sound waves to take into consideration is the fact that as the wave takes a certain amount of time to reach our ear, we have speed of sound.

Historically there was some understanding about vibrations but most thinkers thought that sound was merely a particle that went forward after being ejected from the source until it reached the ear. The Greeks knew quite a lot about vibrating strings and the Roman architect Vitruvius (1st century BC) made the comparison with the pebble in the water but it is not clear whether they understood how it was propagated. They certainly knew that sound travelled and that it travelled slower than light. They observed that a flash of lightning, a bolt from the heavens, perhaps thrown by a god, was seen instantaneously, whereas the sound it made took a little longer to be heard and that was the time it took the sound to travel the distance.

During the Enlightenment (a period so-called because people had begun to throw off the restrictions imposed on them by the Church and State) questioning nature rather than accepting it became more common. A French philosopher and mathematician called Galendi tried to imitate thunder using firearms. He measured the time between the flash and the sound of the explosion as well as the distance it had taken to reach him.

Considering the crudity of his methods, the conclusion he made regarding the speed of sound was surprisingly accurate. Due to technological advancements in this field, we now know that sound travels at around 332 metres (1,089 feet) per second.

Knowing the speed of sound was only a matter of scientific interest until the Second World War when experimental attempts showed that there was no reason why they should not fly at the speed of sound or even faster. Technology had begun to outstrip philosophical thought and scientific speculation as new materials and powerful jet engines became available. However, no one really knew what would happen should an aircraft fly at the speed of sound and there was only one way to find out. The first pilot to carry out the experiment was Captain “Chuck” Yeager of the US Air Force in 1947, aboard an aircraft he called Glamorous Glennis.

Those who took on the task of flying the plane at the speed of sound must have trusted the engineers who built the aircraft. When they actually reached the speed of sound (which was now called Mach 1 after Ernst Mach who was born in what is now the Czech Republic when it was still part of the Austro-Hungarian Empire and worked on shock waves) the result was a dramatic bang. The loud bang was caused by the plane smashing through the particles of air which had become tightly compressed.

I remembering following these developments enthusiastically as a boy through inspiring films that told the story of those brave men. Today, their achievements are mostly forgotten although the potential ill effects of supersonic flight on the environment do generate interest and enthusiasm.

1.1 Measuring Loudness

“Loudness” is such a commonly used word that it seems unnecessary to question its meaning. Yet our descriptions of sensations depend on the language that we use.

We are fortunate with English: because it stems from so many different roots it has acquired an enormous number of words that are available to us.

I once attended a conference in Bordeaux where the organisers insisted I speak in French even though the audience was international, as the organisers had a good system of simultaneous translation. The French have their reasons about these things and I was anxious to cooperate.

During my presentation I could not find the French word for loudness. Colloquially they may say “parlez plus haut” or talk more “highly” which is unhelpful scientifically as the term “high” has to do with pitch rather than loudness. They could say “fort” which means “strong” but implies something different when speaking about sound. They might get around the problem by referring to volume but that, of course, has to do with space. In the end they have to say “le ‘loudness’”!

English, on the other hand, is more flexible and we have permitted the word “loud” to wander into different meanings. For example, its basic meaning is “very audible” but it can also be used to mean an object that is garish or offensive as though it is shouting at you.

In measuring sound, it is important to note that we have different needs at different times.

Psychologists often use a system of ranking attributes using the values 1 to 5 and we can use this system to describe the loudness of a sound:

Just audible	1
Comfortable level for listening	2
Too loud for comfort	3
Unacceptably loud	4
Painful	5

This system is simple and is used in numbering the volume control of many hearing aids, usually with the advice that our patients to keep it on number 2.

Not everyone would be happy with this system. The manufacturers of equipment, for instance, require great precision and may be uneasy at having 1 as the threshold of audibility as people are not identical. Nonetheless their equipment has to be standard.

In the earliest days of the Industrial Revolution, James Watt invented a machine that worked with the power generated by steam. He sold it to his clients by suggesting that they could replace a dozen horses by its use and so the power of the machinery is referred to as 12 horsepower or 12 hp. When machines replaced men rather than horses they could have used “manpower”, but they did not.

Now power comes from such diverse sources that it would be out of place to describe a light bulb, for instance, as hav...