Fundamentals of Speech and Hearing Science: A Primer for Students in Speech-Language Pathology and Audiology
Jay R. Lucker, Ed.D., CCC-A/SLP, FAAA
Professor - Department of Communication Sciences and Disorders
Howard University - Washington, DC
Section One: Introduction & Overview
Chapter One: Components of Speech and Hearing Science
Welcome to your pursuit of speech-language pathology and audiology. There are many things you will learn as you move forward in your studies. Some of these are basic fundamentals you will learn such as the anatomy and physiological of the speech and hearing systems, neuroanatomy and physiology related to these systems, speech and language development, etc. One of the fundamentals relates to the science behind how we produce, transmit, receive, and understand verbal communication (i.e., speech). This textbook presents the fundamentals of this area which we call speech and hearing science. Thus, this book is a primer for you learning about the concepts and ideas involved in the science of how we speak and hear what is spoken to us as well as how speech is transmitted from the source (also called the sender), usually the mouth of the speaker, through the air (known as the medium), and is picked up by our ears and transmitted to our brains via our auditory systems.
When considering these fundamental factors, then, we see that there are essentially four parts of speech and hearing science. One is the sender. The second is the medium through which sound and speech are transmitted from the sender to the receiver. The third is the reception factors of hearing. The fourth and last part involves transmission of what is received by the ear to the brain where it is processed and we make sense of the meaning of that information. Additionally, the brain has mechanisms by which the speech we produce when nerves from the brain and brainstem innervate our speech mechanisms. These general factors can be diagrammed in the following manner:
In this figure, the source is a loudspeaker and the blue represents sound waves in the air. The ear picks up the sound waves and transmits them to the brain where we process what we hear and sets up the neural impulses to innervate our speech mechanisms so we can verbally respond, for example, when someone asks us a question.
In order to study all the science that goes into this production to transmission to reception to comprehension of speech, we need to understand some basic, underlying concepts. This section of the book discusses these basic concepts. The chapters are divided into the Components of Speech and Hearing Science (Chapter 1) and Underlying Terminology in Speech and Hearing Science (Chapter 2). The remainder of this book looks deeper into each of the four components using the terminology presented in this section of the book.
The First Component: The Sender
The first component involves the production of sound which is transmitted through the medium to the receiver. This production occurs whether there is a receiver or no receiver. Thus, if a tree falls in the forest it does make a sound. The philosophers may say, “No” because “making a sound” means someone or something has received the sound. However, in the science of sound (and speech) production, “making a sound” means forming changes in the medium in which the sound is transmitted that produces waves that travel away from the source and can be picked up by a receiver able to “capture” those waves (called sound waves). When it comes to communication, our field of study, the sound waves we are most interested in are speech sound waves. However, we can also transmit non-speech sound waves. Can you think of any sounds you can produce that are not necessarily speech?
The following is a list of possible sounds humans make in the form of your first multiple choice question. Read the list and choose every item if the sound presented is something humans can make that is not speech. That is, sounds are from our vocal mechanisms, but they are not classified as speech.
Check all of the sounds presented if they are made by our vocal mechanisms but are not considered a meaningful speech sound.
Clicking sound like a series of sounds representing the letter “t”
A yawn that sounds like “ah”
What we call “raspberry sounds”
Smacking your lips together making a sucking like sound
Smacking your lips together making a sound like the letter “p”
All these sounds use our vocal mechanisms that we use to produce speech. Each and every one of these sounds (or noises) causes a sound wave to travel through the air into your ears so you can hear the sound. However, none of these sounds is considered meaningful speech. Speech is defined as making oral sounds that follow specific rules of the language with the grouping of sounds resulting in meaningful utterances we call words, with groups of word representing phrases, sentences, and, eventually, discourse. These “meaningful utterances” are considered “language” and represent what we transmit as our thoughts and ideas. sounds, but they really are not speech sounds because they do not represent speech or our desire to represent a meaningful utterance. One could argue that the “raspberry sound” or the “t-t-t” sound represents a meaningful utterance, but most people would not classify these as speech.
When we speak, the first component is the sender. The sender is the source that makes the sound. In the figure we saw before, the sender was a loudspeaker. However, for this book, the sender is usually the person speaking. (Actually, the loudspeaker could be transmitting a person’s speech when we speaking into a microphone, for example.) We will review the general anatomical parts that are involved with the sender in a future chapter in this book. Whatever the sender may be, the one commonality is that it leads to the development of sound waves that are transmitted into the medium in which these waves will travel. For the study of speech and hearing science, the sender will involve those elements of the vocal tract which we will study further later in this book. Thus, the first component is the sender.
The Second Component: The Medium
As previously discussed, the sound produced by the sender leads to waves in the medium through which the sound travels. Typically, this medium is air. When we speak, we talk into the air. What we will learn is how our speech changes the molecules in the air to form the waves that travel out of our mouths and allow the receiver to pick up what we have said. These waves are called the sound waves. The section of this book focusing on the medium will discuss the science involved in sound waves.
Air is not the only medium through which sound travels. Sound waves can also travel through other mediums. What other mediums do you think might allow sound to travel? Answer the next question to check your thinking on this topic.
Through what mediums can sound travel? Below are a series of items. Select all items presented if they are a medium through which sound can travel.
Solid objects like walls or floors and ceilings
Air was already discussed, so if you chose A. Air, you have identified the most common medium through which sound travels. However, have you ever played with your friends while you were swimming and you spoke to each other under water? Did you hear what your friends were saying? Not as clear as when they were speaking out of the water (i.e., in the air), but sound travels through water. Just think of all the mammals that live in the sea sending sounds to other sea mammals. Whales and dolphins are examples of sea creatures that transmit sound though water all the time. Sonar on submarines is a special piece of equipment that receives and measures the sound waves made by other ships and submarines in the water.
In addition to water, sound waves travel from air into the water. Have you ever been underwater and heard someone calling you from above the water? Have you ever yelled out underwater and, later, when you surface, someone says they heard your call? Thus, sound waves travel from air to water and vice versa.
Sound waves also travel through some solids. If sound waves did not travel through solids, how would you know someone was knocking at your door? Wouldn’t it be nice not to have to put up with the noisy party in the dorm room next to yours; what about the people walking like elephants living above you? Sound waves can strike the walls or floors causing them to transmit the sounds through the walls and floors until the waves travel from the opposite side of the walls (or floor/ceiling) into the air on the other side so we can hear the sound. Also, sound waves can be felt when walls vibrate so strongly because the sound waves striking the walls are felt by the person’s hand or bare feet. People who are deaf may say they “felt the sound” when it is vibrating a wall, door, or floor.
Sound waves also travel through solids such as instruments. We hear the beat of the drums and the music coming from guitar and violin strings and from the hammer hitting the strings of a piano when the player touches the keys of that instrument. These are all forms of sound traveling through solids (in these cases) into the air.
The solid objects through which sound waves travel must be solid enough to allow vibration. The sound wave causes the solid object (wall, ceiling, floor, drum head, reed on some instruments) to vibrate. However, soft objects, like whipped cream are not solid enough to vibrate so sound waves would not travel through these objects. However, these objects usually have a lot of air in them, so the sound waves would travel through the air in the whipped cream, but not through the whipped cream itself.
Does sound travel through vacuums? Well, consider the following, what do you think would happen if astronauts on the moon were able to take off their space helmets and spoke to each other. The dialogue would likely be like the dialogue in the figure below:
You should notice there is nothing but empty page space between these two astronauts (and maybe a line where the images were combined). Without some medium such as air, sound waves cannot be produced. Thus, there are no sounds on the moon or in a vacuum. Thus, the philosophers were correct that a falling object makes no sound if they were referring to the moon or some other planet without an atmosphere. Thus, sound waves must have a medium, such as air, and in our discussion of sound waves and the transmission of speech, we will discuss the medium of air since it is our primary medium for transmitting sound.
The Third Component: The Receiver
Once speech (or sound) is transmitted through the medium, such as air, the waves travel through that medium until they are picked up by a receiver. In the field of speech and hearing science, this is where we switch from speech science to hearing science since the receiver is usually the human ear. But, the ear is not the only receiver of sound. Can you think of other receivers of sound?
Which of the following could be a receiver of sound? Choose all items that can be a receiver of sound.
A hearing aid
A cell phone
The receiver is the item that picks up the sound. The most common one we use is the microphone. Hearing aids really do not pick up sound. It is the microphone of the hearing aid that picks up sound. If you identified YES to C and D, your responses are correct, but the real item is the microphone in the hearing aid and cell phone (or any other phone).
Although we hear from TVs and Radios, when we speak to these inanimate objects, they do not pick up what we say unless they have a special microphone and speech analysis system in them. Thus, when we speak through the new systems connected to TVs and Radios (such as car radios), we are really speaking into the microphone on these systems.
The human ear or our auditory system is the most common receiver of speech for which we are concerned as speech-language pathologists and audiologists. The ears of animals are also receivers of sound. In our discussion of the receiver, we will focus on the human ear as that is the receiver of greatest concern to speech-language pathologists and audiologists.
The Fourth Component: The Brain
Most text books and discussions of speech and hearing science end with the third component, the receiver. However, what value is it to know that the ear and auditory system picks up sound (especially speech) if the speech has no meaning? The auditory system does not make sense of any of the sounds it picks up. We will learn that it “decodes” the sounds so that our brains can make sense of the sounds. Thus, the fourth, and final, component of our concern is our brains. Does this mean the Scarecrow in the Wizard of Oz could not understand all the sounds it heard? Obviously, the Scarecrow had a brain even before the Wizard “gave” him one. Just think of how well he sang and danced and reacted to everything that was said and all the sounds the Scarecrow’s ears picked up. Well, if only Dorothy had taken speech and hearing science and had read this book!
Thus, the fourth component is the brain. In a future section we will see an overview of the brain mechanisms that receive the information from our ears and interpret that information into meaningful speech. We will also learn about the brain mechanisms that convert our ideas into language, and language into the neural activities needed to produce speech.
This chapter introduced you to the four basic components of how we produce, transmit, receive, and understand sounds and speech. The remainder of the book will focus on each of these elements and how they contribute to our abilities to speak, hear, and comprehend what we hear. As stated above, the focus is to understand the science behind these components and how this science helps us deal successfully with the clients and patients we serve when you become future speech-language pathologists and audiologists.
Although the focus will be on the normal systems involved in each component, each section will look briefly at what happens if the system becomes abnormal. Our work typically focuses on evaluating speech production and reception (or hearing) as well as the processing of what we hear (auditory processing) and produce with a focus on differentiating between normal and malfunctioning systems.
The format of this book is that it is divided into sections and each section is divided into chapters. This is the first section, the introduction and overview, and this was the first chapter in that section. After each chapter there will be a quiz you can take to insure that you understood the key points brought out in each chapter. At the end of each section, you will be administered an exam that covers information from the entire section. Your professor may grade your quizzes and exams or just the exams. Or, your professor may have you skip the quizzes and exams and present you with different forms of evaluating your abilities to learn the material presented in speech and hearing science. As the title of this books indicates, this book presents the Fundamentals of Speech and Hearing Science.
Go ahead and complete the quiz for this chapter. All questions for quizzes and exams in this book are multiple choice. See if you can achieve 100% correct before proceeding to the next chapter and do this with each quiz. You will be told if your response to each question is correct or incorrect, but you will only be told the correct answers when you choose to submit your answers. You will be able to redo your response to any question before you submit So, check the chapter and redo the questions identified as incorrect. As for the exams, you can only take them once and your grade will be the grade you earned on the one attempt at the exam.