ABSTRACT
Hearing aid device is a small electronic gadget that is fit in or
behind the ear to improve one’s hearing and consequently communication
ability.This research work involves the design and development of a
hearing aid device withpre-amplifier; an acoustic signal picked-up using
a condenser microphone. TDA 2822M IC is configured to produce an audio
amplification which is converted to audio signal through a headphone.
Designed equations were employed to calculate the physical parameters of
the circuit. After the design, the circuit was constructed and tested
on 4 people with partial hearing problem. The result showed that there
was a significant improvement in the hearing ability of all the patients
tested. The final test showed that the device could prove very useful
for people with partial hearing problems. However, the device had no
impact on persons suffering from complete deafness. For further
improvement, it is recommended that a wireless hearing aid device should
be designed and constructed to reduce the weight. The casing of the
hearing aid should be made up of more portable, qualitative and lighter
plastic material so as to reduce the overall weight and size. During the
design, more care should be taken so as to avoid feedback signal
between the microphone and the headphone which may result in noisy
signal.
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND TO THE STUDY
Hearing is one of the five senses along with vision, taste, smell
and touch. The ear serves asa receiver of incoming sounds. Although the
ear receives sound and is the sense organ for 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 (Kinsler, Frey, Coppers, and
Sanders, 1982). Although the sensation of hearing requires an intact and
functioning auditory portion of the central nervous system as well as
working ear, human deafness (extreme insensitivity to sound) and hearing
loss most commonly occur because of damages of the ear, rather than the
central auditory system.
Hearing aid device is a small electronic gadget that is fit in or
behind the ear to improve one’s hearing and consequently communication
ability (Yusuf, 2015). While some people are born with hearing problem
some others develop it as they grow. This problem can occur as a result
of disease, aging, and injury from noise or intake of certain medicines
(N.I.D.C.D, 2010). Hearing problems could be that of complete deafness
or partially impaired type. Hearing problem could occur after a person
learned to talk (post lingual) or those with trilingual deafness that
is, deafness that occurs before a person learns to talk. Deafness,
whatever the degree or course, is generally a source of worry and
frustration to the patient concerned as it affects almost all aspects of
one’s life.
Hearing loss is usually reserved for people who have relative
insensitivity to sound in the speech Frequency range. A hearing loss can
happen when any part of the auditory system is not working in the usual
way (Oyler, R., Oyler, A., and Matkin,, 1988).
The design and constructed hearing aid device can improve the
quality of sound for people with hearing loss. The heart of the circuit
is an integrated circuit 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. The amplification function of the hearing
aid is made possible with several components; a microphone (input
transducer) which picks up sound an amplifier which increases the volume
or the sound, a receiver (output transducer) which changes the
electrical signal back into sound and sends it to the ear
(Lowenberg,1976).
Hearing aids have been available in four styles: body, eyeglass, behind-the-ear (BTE), and in-
the-ear (ITE) hearing aid. Included in the category of ITE hearing
aids are in-the- canal (ITC) and completely-in-the-canal (CIC) styles.
While body and eyeglass style hearing aids were regularly used 40-50
years ago, they comprise only about 1% of all hearing aids marketed
today. Instead, most individuals choose ITE (approximately 80%) or BTE
(approximately 20%) style hearing aids. This transition in style, use,
and preference is occurring for a number of reasons, including the
reduction in the size of the components, durability, and cosmetic
concerns on the part of the consumer (Gus and Ruth, 2005).