Transcript ppt - King Fahd University of Petroleum and Minerals

King Fahd University of Petroleum and Minerals
Electrical Engineering Department
EE 445
Course Presentation
062
Natheer Al-Nasr
[email protected]
Introduction
Human Senses
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Seeing
Hearing
Taste
Touch
Smell
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Hear Loss
Why do people lose their hearing?
Medically, there are two major types
of hearing loss:
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Conductive hearing loss
involves the outer and middle ear.
Results: a wax blockage, birth defects, ear infections, or it may
be genetic.
Corrected surgically.
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Sensorineural hearing loss
involves damage to the inner ear.
Caused by aging, birth-related problems, viral and bacterial
infections, genetics, exposure to loud noises.
Corrected with a hearing aid.
Hearing Aids
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Outline
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Definition
History of Hearing Aids
Types
Parts
How it Works?
Hearing Aids
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Definition
• A hearing aid is an electronic, battery-operated
device that amplifies and changes sound to allow
for improved communication.
Hearing Aids
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History of Hearing Aids
• The earliest hearing aid was the ear trumpet. (horn)
• In the 1950s, transistors replaced amplifier tubes and smaller
magnetic microphones became available.
Hearing Aids
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Types
• There are four types of modern Hearing aids:
1. Behind-the-ear
2. In-the-ear
3. In-the-canal
4. Completely-in-the-ear
Hearing Aids
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Types
Hearing Aids
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Types
Hearing Aids
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Parts
• Hearing aids consist of:
1. A microphone, to pick up sound.
2. An amplifier, to make the sound louder.
3. A speaker, to deliver the sound into the ear.
4. Batteries, to power the hearing aid.
Hearing Aids
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How Hearing Aids Works?
• Most of Hearing Aids works in this way:
– The microphone converts sound into a varying
electrical current.
– The amplifier amplifies this current.
– The earphone converts the amplified current
into a sound of greater intensity than the
original.
Hearing Aids
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How Hearing Aids Works?
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After switching S to ‘on’ position
the condenser microphone detects the sound signal.
It 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.
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http://www.uthearingaids.com/hearaid/whatishaid.htm
http://www.nidcd.nih.gov/health/hearing/hearingaid.asp#6
http://www.ftc.gov/bcp/conline/pubs/health/hearing.htm
Hearing Aids
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