Design Of A Device For Speech Aid (For Laryngectomy Patients)

ABSTRACT

The larynx is an organ in the human respiratory system that forms the basis of the speech production system. According to world health organisation (2019), every year, many thousands of people worldwide lose the ability to speak due to receiving a laryngectomy, typically for treatment of cancer. At some point in their recovery, most will use an electrolarynx to recover their ability to speak.

This device offers the potential to greatly improve the lives of those who have lost their voices and must rely on technology to allow them to communicate in the most efficient manner. An Electrolarynx is an electronic speech aid that enables the Laryngectomee to communicate with other people as quickly as possible after the successful removal of the larynx. A neck type Electrolarynx has been designed. Earlier designs could not alter frequency and intensity simultaneously during conversation. The Electrolarynx developed can control both frequency and intensity simultaneously during conversation. The device has been tested on the patient and found to be very effective. A portable, pocket size, battery powered voice amplifier (PA system) has also been developed which uses an electric condenser microphone as the input. The voice amplifier developed is a two stage amplifier which uses a preamplifier stage and a power amplifier stage. The output of the power amplifier is connected to a speaker. The device is being used by the patient and found to be very useful.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE STUDY
• PROBLEM STATEMENT
• AIM AND OBJECTIVE OF THE STUDY
• PURPOSE OF THE STUDY
• SIGNIFICANCE OF THE STUDY
• SCOPE OF THE STUDY
• LIMITATION OF THE STUDY
• APPLICATION OF THE STUDY
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

• INTRODUCTION
• THE FUNDAMENTALS OF SPEECH
• ANATOMY OF THE LARYNX AND TRACHEA
• CHARACTERIZATION OF SPEECH
• OVERVIEW OF LARYNGECTOMY
• OVERVIEW OF VOICE RESTORATION
• HISTORY OF VOICE RESTORATION
• DESCRIPTION ELECTROLARYNX
• HISTORY AND EVOLUTION OF AN ELECTROLARYNX
• REVIEW OF VARIOUS TYPES OF SPEECH AID DEVICES

CHAPTER THREE

METHODOLOGY

• METHOD USED
• SYSTEM BLOCK DIAGRAM
• TRANSDUCER SELECTION AND RESONANT FREQUENCY IDENTIFICATION
• CIRCUIT DESIGN
• FABRICATION AND ASSEMBLY

CHAPTER FOUR

4.0      TEST AND RESULT ANALYSIS

• VALIDATING THE DEVICE
• TESTING THE DEVICE
• EXPERIMENTAL SETUP
• RESULTS
• DISCUSSION

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION AND FUTURE WORK
• REFERENCES
• CHAPTER ONE

1.0                                                             INTRODUCTION

1.1                                               BACKGROUND OF THE STUDY

Voice is known as a powerful mechanism to express ourselves. Voice production is an organized control of sensory and motor nervous systems (Simonyan and Horwitz, 2011). The cortical and subcortical areas of the brain control the speech production system. The lungs, larynx, vocal tract, and oral cavity are the main motor organs for speech production in human beings (Ackermann et al., 2014). The energy for producing speech originates from the lungs through the exhalation of breath. This vibrates the larynx and produces regular movement, resulting in laryngeal vibrations known as glottal waves (Bouchard et al., 2016). These periodic movements resonate, and intelligible speech is produced by the articulators in the oral cavity, such as the tongue, teeth, and lips (Visser, 2006).

A person loses his ability to speak when the larynx is removed surgically due to unavoidable circumstances, such as laryngeal cancer. The electrolarynx is an electro-mechanical device that acts as a larynx substitute which is an artificial device.

The first artificial larynx was a pneumatic device produced in 1859 by Johann Nepamuk Czermak of Pesth to treat complete laryngeal stenosis. The first human laryngectomy was performed by Patrick Watson of Edinburgh in 1866; the first use for cancer was in 1873 by Theodor Billroth who also installed a pneumatic powered reed device for restoring the patient’s voice. The first true electrolarynx was developed by Themistocles Gluck in 1910; it used an Edison style phonograph with a recording of a vowel sound which was played using a telephone receiver. [P. W. Alberti, 2015] Over the years improvements were made to Gluck’s basic design; however, it wasn’t until the invention of the transistor in the 1950’s that the design evolved into the piston style device still used today. The design still utilized a telephone speaker derived electromechanical driver but attached a rigid disk to impart vibrations into the vocal tract. Modern implementations have the driver strike a flat disk which is pressed to the neck; this results in nonlinear impulse excitations. This design imparts higher amplitude signals into the vocal tract, but due to the nonlinear transducer, the characteristics – such as spectral envelope, wave shape, and dispersion – which can be easily controlled are limited. [S. Bien, 2008]

Being a battery-driven device, an electrolarynx’s size should be as small as possible. However, battery technology is not advanced enough for new technology, so alternative energy-saving methods must also be accommodated (Madhushankara et al., 2015; Fuchs et al., 2016; Sofyan et al., 2016; Ejidokun et al., 2018). In our research, we designed an energy-efficient electrolarynx by modifying the driving source, thereby reducing battery size, which is proportional to battery capacity. We also employed li-ion batteries, which are commonly found in mobile phones due to their light weight and high energy capacity.

The main aim of this work is to design a novel electrolarynx which utilizes two interfering ultrasonic waves to generate a fundamental frequency in the vocal tract required for speech restoration. The device is light weight, compact, inexpensive, and offers excellent control of all aspects of the output waveform.

1.2                                                      PROBLEM STATEMENT

Traditional electrolarynxes utilize a piston to strike a disc pressed to the patient’s neck which delivers a pressure wave into the soft tissue. This pressure wave mechanically couples with the vocal tract and generates the fundamental frequency necessary for creating vowels without which speech is not possible.

Commonly available electrolarynxes suffer from poor frequency control due to the nonlinear character of their impulse driver. They also create a great deal of “self- noise” which is distracting to listeners and makes using voice communication systems difficult.

In this study we propose a novel electrolarynx implementation which utilizes two interfering ultrasonic waves to generate a fundamental frequency in the vocal tract required for speech restoration which overcomes the problem noticed on the traditional electrolarynx. The device is light weight, compact, inexpensive, and offers excellent control of all aspects of the output waveform. In addition, as the primary waveforms are above human hearing, there is little “self-noise” that can be heard by listeners and most communications devices filter such noise as part of their standard digitization process.

1.3                                          AIM AND OBJECTIVE OF THE STUDY

The main aim of this work is to build an electrolarynx which is a device used by most laryngectomees to regain their verbal communication. The objectives of the study are:

1. To design an electrolarynx which utilizes two interfering ultrasonic waves to generate a fundamental frequency in the vocal tract required for speech restoration.
2. To build an electrolarynx to accommodate various driving signals.

• To enhance communication.

1. To provide an understanding of the importance of voice restoration after total
2. To discuss how the electrolarynx may be used to restore voice following total laryngectomy.
3. To outline some of the current electrolarynx devices available, including their mechanism of action and

1.4                                                     PURPOSE OF THE STUDY

The purpose of this study is to provide an alternative speech rehabilitation method to the totally-laryngectomized patients that will generate vibrations of fundamental frequency of human vocal cords.

1.5                                                 APPLICATION OF THE STUDY

This device can be applicable not only for a laryngectomy patient but also for a person who has lost their ability to speak due to various other reasons.

1.6                                                SIGNIFICANCE OF THE STUDY

This research work will throw more light on the techniques for voice restoration, rehabilitation in a more efficient manner . This study will also be designed to be of immense benefit to all the users of electric motor most especially in industries.

The study has also made us to have understanding of the importance of voice restoration after total laryngectomy.

1.7                                                        SCOPE OF THE STUDY

This study is on speech aid device known as electrolarynx, sometimes referred to as a “throat back”, is a medical device about the size of a small electric razor used to produce clearer speech by those people who have lost their voicebox, usually due to cancer of the larynx. The most common device is a handheld, battery-operated device pressed against the skin under the mandible which produces vibrations to allow speech; other variations include a device similar to the “talk box” electronic music device, which delivers the basis of the speech sound via a tube placed in the mouth. We propose a novel electrolarynx implementation which utilizes two interfering ultrasonic waves to generate a fundamental frequency in the vocal tract required for speech restoration. The device is light weight, compact, inexpensive, and offers excellent control of all aspects of the output waveform. In addition, as the primary waveforms are above human hearing, there is little “self-noise” that can be heard by listeners and most communications devices filter such noise as part of their standard digitization process.

This device offers the potential to greatly improve the lives of those who have lost their voices and must rely on technology to allow them to communicate in the most efficient manner.

1.8                                                  LIMITATION OF THE STUDY

Although all speech aid devices have focused on producing the sound from the patient’s vocal tract, they were found to be less effective .This is because the speech produced by them accompanies with a noise which is probably more than the speech. This leads to the inefficient regain of the lost speech for laryngectomy patients.

1.9                                                    PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work,   chapter two presents the literature review of the study,  chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.