LOW COST HEARING AID
MICROPROJECT REPORT
S3EA
Submitted by
MEGHA R
Reg No:MAC19EE080
MERIN MARY JOSY
Reg No:MAC19EE081
PELI ADO
Reg No:MAC19EE087
NABEELA FYROOSE K A
Reg No:MAC19EE085
REEMA S
Reg No:MAC19EE091
CIRCUITS AND MEASUREMENTS LAB (EEL201)
Department of Electrical and Electronics Engineering
Mar Athanasius College of Engineering
Kothamangalam
ACKNOWLEDGEMENT
First and foremost, praises and thanks to God, the Almighty, for His showers of blessings
throughout our work which enabled us to complete the project successfully.
We would like to express our deep and sincere gratitude to Prof. Honey Susan Eldho,
Assistant Professor, Department of Electrical & Electronics Engineering for her
enthusiasm, patience, insightful comments, helpful information, practical advice and all
other members of the Department of Electrical & Electronics Engineering for sharing their
valuable comments about our microproject.
We are also grateful to Prof. Beena M Varghese, Head of Electrical & Electronics
Engineering Department for her valuable guidance. Her immense knowledge, profound
experience has enabled us to complete this project successfully.
We are deeply indebted to Dr Mathew K, Principal, Mar Athanasius College of
Engineering, for his encouragement and support.
We also pay our respects and love to our parents for their love and encouragement
throughout our project. Last but not the least we express our thanks to our friends for their
cooperation and support.
CONTENTS
Chapters
Page No.
CHAPTER 1. ABSTRACT
4
CHAPTER 2. INTRODUCTION
2.1 Block Diagram
2.2 Components Required
2.3 Circuit Diagram
5
6
6
7
CHAPTER 3. DESIGN AND SIMULATION
3.1 Design
3.2 Simulation
8
8
9
CHAPTER 4. CONCLUSION
4.1 Advantages
4.2 Conclusion
REFERENCES
10
10
10
11
CHAPTER 1
ABSTRACT
Hearing is one of the five senses that completes a human being. However, owing to old age or
accidents people may suffer from loss of hearing. Hence, we have come up with a low-cost
hearing aid to the rescue of the common man. Our project deals with the basic principle of
converting a voice impulse into electrical signals using a transducer. The setup will run at a 3V
battery supply. The signal will be pre-amplified using an NPN transistor. Finally, the desired
output will be received via earphones at the receiving end. We are using Proteus Design Suite
8 software for designing and simulation our circuit. The Proteus Design Suite is a proprietary
software tool suite used primarily for electronic design automation.
CHAPTER 2
INTRODUCTION
Hearing is one of the five senses along with vision, taste, smell and touch. The ear serves as a receiver
of incoming sounds. Although the ear receives sound and is the sense organ of hearing, it is the brain
and central nervous system that interpret the sound. The human auditory system can generally hear
sounds within the frequency range of 20 Hz and 20 kHz but the frequency range between 100Hz and 6
kHz contains most of the information of human voice. Although the sensation of hearing requires an
intact and functioning auditory portion of the central nervous system as well as working ear, human
deafness and hearing loss most commonly occur because of damages of the ear, rather than the central
auditory system. A hearing loss can happen when any part of the auditory system is not working in the
usual way. The constructed device can improve the quality of sound for people with hearing loss. The
heart of the circuit is the transistors which amplifies all the signals picked by the condenser microphone
and converts them back into sound and sent to the ear. It is a battery-powered electronic device that can
amplify sound for people with hearing loss.
2.1 BLOCK DIAGRAM
The battery supplies the power to turn the electronic components on and off. The 3 volt battery was used
for the power supply. The condenser microphone was used in this work. The primary function of a preamplifier is to pick up signals from its primary source (microphone) and then operate on it, in preparation
for passage into the amplifier section for further amplification. Typically, a pre-amplifier amplifies the
signal, controls its volume, and perhaps changes its input impedance. The pre-amplification unit used in
this work was designed using an NPN transistor along with some capacitors and resistors. In this circuit,
transistor Q 1 and its associated components form the audio signal pre-amplifier for the signals picked
up by the condenser microphone and the audio signal is converted into corresponding electrical signals.
Resistor R1 biases the internal circuit of the low-voltage condenser microphone for proper working. The
audio output from the pre-amplifier stage is fed to the input of the amplifier circuit via capacitor C3.
2.2 COMPONENTS REQUIRED
1. Transistor BC549, BC548, BC558
2. Resistor 220ohm, 1.5 K, 2.2 K, 3.3 K, 100 K, 220 K, 680 K
3. Capacitor 0.1u, 1u 10V, 100u 10V
4. Condenser Microphone
5. Speaker
6. Battery 3V
7. Switch
2.3 CIRCUIT DIAGRAM
Circuit Diagram
The circuit diagram of hearing aid is shown in the above figure 2.3. It is built around PNP and NPN
transistors, resistors, capacitors and few other components. The circuit can be easily assembled on a
small, general-purpose PCB or a Vero board. It operates off a 3V DC supply. For this, you may use two
small 1.5V cells. Keep switch S to OFF state when the circuit is not in use. On moving power switch S
to ‘on’ position, the condenser microphone detects the sound signal, which is amplified by transistors T1
and T2. Now the amplified signal passes through coupling capacitor C3 to the base of transistor T3. The
signal is further amplified by pnp transistor T4 to drive a low impedance earphone. Capacitors C4 and
C5 are the power supply decoupling capacitors.
CHAPTER 3
DESIGN AND SIMULATION
The software used for simulation is Proteus Design Suite. The Proteus is an electronic circuit
design software which includes a schematic capture, simulation and PCB (Printed Circuit
Board) Layout modules. The software is used mainly by electronic design engineers and
technicians to create schematics and electronic prints for manufacturing printed circuit boards.
3.1 DESIGN
Proteus Design Suit is used for the simulation. The Proteus Design Suite is a Windows
application for schematic capture, simulation, and PCB (Printed Circuit Board) layout design.
The circuit is designed as shown in figure 3.1. The fig shows the circuit in its ON position.
Design
3.2 SIMULATION
When the switch is set to ON position the condenser microphone receives the input sound signal. The
transistors amplify the signal and output is obtained at the speaker. When the output terminal was
connected to an oscilloscope, the following graph 3.2 was obtained from the oscilloscope. Thus, the signal
is amplified and sensed by the ear with the help of the hearing aid.
Simulation
CHAPTER 4
CONCLUSION
4.1 ADVANTAGES
Commercially available hearing aids are quite costly. Here is a low-cost hearing aid circuit that uses just
four transistors and a few passive components. These are of great use for them who are impaired with
low hearing. This low-cost hearing aid circuit offers the advantages of high sensitivity, low current
consumption and light weight.
4.2 CONCLUSION
In this project we have discussed about low cost hearing aid circuit. Our microproject was designed in
Proteus Design Suite. The simulation was also done in the same software.
It was possible to design a hearing aid with the components that are easily available. These type of hearing
aids are much beneficial for the common man. The device was realized with economic considerations so
that it is cost-effective, could be made readily available and with easy maintenance. It is recommended
that this hearing aid could be subjected to some modifications by using filters to enhance efficiency and
better quality
By the rendition of such an experiment, the practical application and working of a hearing aid in circuits
and measurements lab was understood.
REFERENCES
1. https://www.electronicsforu.com/electronics-projects/hardware-diy/hearing-aid-2-2
2. https://www.ijser.org/researchpaper/DESIGN-AND-CONSTRUCTION-OF-A-LOWCOST-HEARING-AID.pdf
3. https://www.eleccircuit.com/the-cheap-small-hearing-aids-project/
4. Akande, S.F., Kwaha, B.J., and Alao, S.O. (2007). Fundamentals in Electronics. Jos: Jos
University Press Ltd, 191p
5. Oyler, R., Oyler, A., and Matkin, N. (1988). Unilateral hearing loss: Demographics and
educational impact. American Speech-Language-Hearing Associatio
6. Lowenberg, E.C. (1976). Schaum’s Outline of Theory and problems of Electronic Circuits.
New York: Mcgraw- Hill Book Company, 274p