Design And Construction Of A Telephone Earpiece

ABSTRACT

This work is on a telephone earpiece which is a device that converts electrical energy into sound energy. Electrical energy from a microphone sets up a varying electric current where frequency is the same as that of the sound made by the person making a call. The electric current is fed into the receiver through transmission telephone wires and the person receiving the call hears the speech. The device consists of speech coil D wound round soft iron cores. The cores are arranged to stick to a permanent magnet M and a thin soft iron diaphragm L is in front of them (may be a paper impregnated with iron filings). As the speech current varies, it causes a variation in the strength of the magnetic field due to the cores, which acts as the electromagnet. This variation causes the diaphragm L to vibrate due to the attractive forces from the electromagnet. The vibrations so produced are of the same frequency as the speech current. The vibrating diagram therefore disturbs the air in the neighborhood, creating sound waves of the same frequency in air which is heard by the person receiving the call. The aim of this work is to construct a telephone earpiece using locally made available materials.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

• PROBLEM STATEMENT
• OBJECTIVES OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• LIMITATION OF THE PROJECT
• SCOPE OF THE PROJECT
• APPLICATION OF THE PROJECT
• RESEARCH QUESTION
• METHODOLOGY
• DEFINITION OF TERMS
• PROJECT ORGANISATION

CHAPTER TWO – LITERATURE REVIEW

2.1      AN OVERVIEW OF A TELEPHONE

2.2      OPERATION OF EARLY TELEPHONE

2.3      WORKING COMPONENTS OF THE TELEPHONE

2.4      HISTORICAL BACKGROUND OF EARPIECE

2.5     EFFECT OF TELEPHONE EARPIECE NOISE ON HEARING

CHAPTER THREE

3.0         METHODOLOGY

3.1        OPERATION OF TELEPHONE EARPIECE

3.2        CONSTRUCTIONAL DETAILS OF A TELEPHONE EARPIECE

3.3       USES OF ELECTROMAGNET – TELEPHONE EARPIECE

CHAPTER FOUR

4.0       RESULT ANALYSIS

4.1      CONSTRUCTION PROCEDURE AND TESTING

4.2      ASSEMBLING OF SECTIONS

4.3     TESTING OF SYSTEM OPERATION

CHAPTER FIVE

• CONCLUSIONS

5.2    REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                               BACKGROUND OF STUDY

Electromagnets have a wide variety of uses. A summary of the principles of operation of some of the important devices in a few major areas of application—communications, research, electrical industry, and magnetic recording.

Modern telephone systems are based on the reed relay, together with solid-state circuits for complex routing of connections. The telephone receiver (earpiece) is basically an electromagnet with a U-shaped yoke having coils wound on each leg of the U. Passage of the electrical signal through the coils causes magnetic attraction of a soft-iron diaphragm supported a small distance from the ends of the U. The diaphragm is deflected by an amount proportional to the magnitude of the current in the coil and generates sound waves as it moves back and forth. Improvement in magnetic materials has increased the sensitivity of the telephone receiver, but the basic design has remained unchanged.

The Telephone Earpiece also known as the receiver serves as an electric mouth. Like a human voice, it has vocal cords. The vocal cords of the receiver are a diaphragm. Two magnets located at the edge of the diaphragm cause it to vibrate. One of the magnets is a permanent magnet that constantly holds the diaphragm close to it. The other magnet is an electromagnet. It consists of a piece of iron with a coil of wire wound around it. When an electric current passes through the coil, the iron core becomes magnetized. The diaphragm is pulled toward the iron core and away from the permanent magnet. The pull of the electromagnet varies between strong and weak, depending on the variations in the current. Thus, the electromagnet controls the vibrations of the diaphragm in the receiver.

1.2                                   PROBLEM STATEMENT

This study was carried out to overcome challenges observe in building a locally made earpiece. This problem is mainly due to unavailability of materials used for the construction. The construction of the telephone earpiece was carried out using locally made available material.

1.3                                            OBJECTIVES OF THE PROJECT

The objectives of the study are:

1. To build a telephone earpiece using available materials
2. To study the working principle of electromagnetism

• To study the function of earpiece in a telephone system.

1.4                                         SIGNIFICANCE OF THE PROJECT

Having a telephone earpiece is a convenient way of listening to your call or music from your telephone. Working on this study will serve as a means of studying the operation of an earpiece.

The study will expose the reader, including the student involved on how an earpiece is been made.

1.5                                           LIMITATION OF THE PROJECT

Telephone earpiece has exploded in popularity, and is the easiest way to play music in your smartphone. The problem is the speakers are usually a bit small and the sound doesn’t quite fill a room.

1.6                                                 SCOPE OF THE PROJECT

The scope of this work covers the building of a telephone earpiece. The system components used are:  permanent magnet, leads, magnet alloy, solenoid and soft iron. The system, which maintains 20-WRMS output power, can be controlled either with a handset.

1.7                         APPLICATION OF THE PROJECT

1. It is used in various types of high-quality Bluetooth stereo headphones.
2. It is used in stereo speakers, stereo.

• All kinds of telephone devices.

1.8                                                        METHODOLOGY

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Test for continuity of components and devices,

• Studying of various component used in circuit.

1. Construct a earpiece circuit.
2. Finally, the whole device was cased and final test was carried out.

1.9                                                   RESEARCH QUESTION

1. How does a telephone earpiece work?
2. How do electromagnet works in telephone?

iii. What are the applications of telephone earpiece?

1.10                                               DEFINITION OF TERMS

EARPIECE: is a small piece of equipment that you put into your ear to hear a recording, message etc.

dBA: Decibels of sound pressure level measured using the A-weighting network; a level intended to measure low-intensity noise (around 40 phon loudness level) but has become commonly used also for measuring occupational and environmental noise exposures.

dBHL: Decibels of hearing level at a certain frequency; a level used to measure audiometric hearing threshold relative to the level defined as normal.

Sound dose: The total quantity of sound received by the human during a specified period. In the context of the WHO-ITU Global standard, it is the same as sound exposure. The unit of (sound) dose is Pa2h.

Dosimetry: The calculation and assessment of the sound dose received by a human.

Equal energy principle: The assumption that equal amounts of sound energy will cause equal amounts of sound-induced permanent threshold shift, regardless of the distribution of the energy across time.

Listening device: A device used to transmit sound to the ear. Consists of a transducer and fitting to accommodate in the ear, on the ear or over the ear listening. Examples are headphones and earphones.

Media: Audio or audiovisual content for entertainment, whereby long term exposure may result in hearing loss. Examples are music, gaming and podcasts.

Personal audio device: A portable device designed to be worn on the body or in a pocket. It is designed to allow the user to listen to various forms of media.

Personal audio system: A system comprising a personal audio device and a listening device.

Safe listening device: A personal audio device/system that meets requirements and criteria to minimize users’ risk of acquiring hearing loss, (as a consequence of its use) can possibly be termed a “safe listening device”. It could include music players (MP3 players, smartphones and personal music players), which together with a transducer can convert an electric signal into audio (e.g. earphones and headphones).

Sound allowance: A dose estimate of sound exposure over a certain rolling period of time (e.g., daily or weekly), commonly expressed in percentage of the maximum regarded as safe. A weekly sound allowance is equivalent to 100% cumulative sound dose.

Sound-induced: Refers to a state or a quality resulting from exposure to sound. The sound may be (part of) music or “noise”, which implies the sound is not desirable.

Transducer: An electronic device that converts energy from one form to another.

1.11                                      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.