Department of Collegiate and Technical Education
GOVERNMENT POLYTECHNIC BELGAUM
Electronics and Communication Engineering
APPLICATIONS OF ELECTRONICS
ENGINEERING ( V Semester)
BY MEGHA B M
BE, M Tech, (Ph.D.)
SENIOR GRADE LECTURER (E&C)
Electronics and Communication Engineering – 15EC54T
APPLICATION OF ELECTRONICS
ENGINEERING
BY MEGHA B M
BE, M.Tech, (Ph.D.)
SENIOR GRADE LECTURER (E&C)
GOVT. POLYTECHNIC BELAGAVI
UNIT 3: AUDIO SYSTEMS
• Terminologies
Audio signal, amplifier, bass control, treble control, decibel
• Microphone
Principle of operation
Types & features – Carbon, Crystal, Moving coil (Dynamic),
Ribbon (Velocity), Capacitor, Electret, Gun, Lavaliere, Tie-clip, Wireless
• Headphones
Principle of operation
Types & features – Moving iron, Crystal, Dynamic, Electrostatic & Electret
• Loudspeakers
Features of basic loudspeaker
Crystal loudspeaker
Woofers
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MICROPHONE
➢ Microphones are audio – electrical
converters.
➢ These are transducers which detect sound
signals and produce an electrical image of
the sound.
➢ These produce a voltage or a current
proportional to the sound signal.
➢ The most common microphones for musical
use are dynamic, ribbon, or condenser
microphones.
➢ These can be designed with different
directional patterns and different
impedances.
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WORKING OF CARBON MICROPHONE
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CARBON MICROPHONE
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INSET OF CARBON MICROPHONE
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FEATURES OF CARBON MICROPHONE
• Convenient size, low cost mass production
• Used in classical telephony systems
• Its operation depends upon the variation in contact resistance of the
carbon granules when subjected to pressure changes of sound waves.
• Movement of diaphragm vary resistance of granules and so control line
current with respect to sound
• These are best at 60 to 7000Hz & non directional
• The non linear distortion results in masking of higher frequency
components by lower frequency harmonics.
• It generates continuous hiss due to variations in contact resistance that
exist between carbon granules.
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CRYSTAL MICROPHONE
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CRYSTAL MICROPHONE
➢ The crystal microphone uses a thin
strip of piezoelectric material attached
to a diaphragm.
➢ The two sides of the crystal acquire
opposite charges when the crystal is
deflected by the diaphragm.
➢ The charges are proportional to the
amount of deformation and disappear
when the stress on
the crystal disappears.
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FEATURES OF CRYSTAL MICROPHONE
• Certain crystals like Rochelle salt and Quartz possess the property of
generating small emf’s when subjected to stress/strain which is
encashed in crystal microphone
• Sound pressure waves press and release the crystal
• Two slices are cemented together such that when pressure is exerted
one slice is compressed while other is stretched like cells of a battery
which doubles the output called bimorph
• Several crystal elements sealed together gives multimorph
• These are best at 50 to 10000Hz & non directional
• Widely used at low cost installations
• Crystals are not durable. Their behaviour change due to humidity, high
temperature and undergo fracture when subjected to shock
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DYNAMIC (MOVING COIL) MICROPHONE
➢Sound moves the cone and the
attached coil of wire moves in
the field of a magnet.
➢The generator effect produces a
voltage which "images"
the sound pressure variation.
➢It is characterized as a pressure
microphone.
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DYNAMIC MICROPHONE
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DYNAMIC MICROPHONE
In dynamic microphones (moving-coil
microphones), a coil of wire surrounds a
magnet and is connected to a
diaphragm which vibrates in response to
incoming sound waves.
When sound waves hit the diaphragm,
the coil oscillates back and forth past
the magnet, generating a current which
creates the audio signal.
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FEATURES OF MOVING COIL MICROPHONE
• These work on the principle of generators
• The diaphragm carries a coil of wire placed in an intense magnetic
field of constant value (B)
• Sound pressure changes result in emf E α Blv
• Its necessary to keep the mass of cone and coil as small as possible
hence aluminium of very fine gauge and limited number of turns is
used.
• These are more reliable and robust hence used for hard usage
• Usually non directional but better performance when microphone
faces directly towards the source of sound
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MOVING COIL MICROPHONE
• Advantages:
Relatively cheap and rugged.
Can be easily miniaturized.
• Disadvantages:
The uniformity of response to
different frequencies does not match
that of the ribbon or condenser
microphones.
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REFERENCES
• Book - S P Bali, “Consumer Electronics”, Pearson Publishers
• https://www.youtube.com/watch?v=cBVm0Q75C3U&t=25s
• https://www.youtube.com/watch?v=yQL5b-aNCKU&t=21s
• https://www.youtube.com/watch?v=_yYBiHjXaLE
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THANK YOU
ANY QUERIES ??
FEEL FREE TO DROP MAIL at
megha.mayani@gmail.com
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