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).
1.2 STATEMENT OF THE PROBLEM
The number of people with hearing loss is rising due to global population and longer life expectancies. A report by world health organization reveals the following: – (WHO, 2005)
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• Two hundred and seventy eight (278) million people worldwide have moderate to profound hearing loss in both ears
• One – quarter of hearing loss cases begin during child hood and detecting and responding to this problem at early stage is vital for development of speech and language by these group of children
• Although properly design and fitted hearing aid can improve communication in 90% of people with hearing impairment, current annual production of these aids meet less than
10% of the global need.
Moreover, the cost of available designs is beyond the reach of most people with this ailment. Hence there is need to increase the affordability and availability of hearing aids for the benefit of this large population with hearing impairment
1.3 AIM AND OBJECTIVES
The aim of this project is to design and construct a hearing aid and, the objectives are as follows:
i. To design hearing aid
ii. To construction of the designed hearing aid and
iii. To test the constructed device
1.4 SIGNIFICANCE OF THE STUDY
In our society there are so many individuals with one level of hearing impairment or the other, who do not pay any significant attention to their problem. One way to ascertain whether you have hearing impairment is to check if you fall into one or more of the categories stated below.
i. If you have difficulty hearing conversation in a fairly noisy environment
ii. If you often ask people to repeat themselves
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iii. If you turn up the volume of radio or television set when others hear comfortably
iv. If you have difficulty hearing whispers and low pitch sounds
v. If you hear loud sounds/voices as whisper etc.
With the above check-list in place, this study will first and foremost expose the need for individuals to pay attention to early signs of hearing impairment so as to take necessary action. Furthermore, the design and construction of hearing aid using locally available materials will raise hope for individuals who cannot afford the price of the sophisticated hearing aid style.
1.5 SCOPE AND LIMITATION OF THE STUDY
Hearing aid can be broadly categorized as acoustic or electronic hearing aids. Electronic hearing aids has different styles, which include
• Body aid
• Eyeglass aid
• Behind-the ear
• In the-ear
• In the canal
These styles can be digital or analogue.
The scope of this project is to design a body aid electronic hearing aid using analogue components.
The limitation of this device is that it may be bulky due to wire connection of components, more so, ear molds which helps to secure hearing aid to the patients ear is not included in the design, Lastly the device with only improve sound for those with hearing impaired situations and not to correct permanent impairment.
