Transcript Chapter 6 Microphones

Narnarayan Shastri
Institute Of Technology
SUBJECT:- AVS
FACULTY:- Malhar Chauhan
FIELD:- E.C SEM-5TH
TOPIC:- Types Of Microphones
Prepared By,
PATEL TIRTHAL D{130340111022}
JOSHI PARSHAD C{130340111010}
MANIRATNAM MUDALIAR P{130340111014}
Introduction
• A microphone is a type of transducer.
• Early microphones were invented for communication
purposes.
• Later modifications were made to design as the microphone
was used more in entertainment industry.
• Different situations call for the need of different microphone
designs as well different pickup patterns.
• Need to consider factors such as the source, the location of
the source and the environment of the source.
Overview of a Microphone
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

Diaphragm—part of microphone which receives the vibration from
sound waves.
Thickness and material of diaphragm are changed depending on the
sound waves you wish to pick up.
Principle working of microphone:
Electrical circuit is used to change these detected vibrations
into an electrical signal that “images” the sound with an
output voltage or current.
• Transducer: device that changes one form of energy into another
• Mics and speakers: sound to electrical signal
Types of microphone
1.Moving coil microphone.
2.Ribbon microphone.
3.Crystal microphone.
4.Carbon microphone.
5.Capacitor microphone.
6.Piezoelectric Microphone.
7.Laser Microphone.
8.Fiber Optic Microphone.
9.Microelectromechanical Microphone.
10.Electret Microphone.
Dynamic Microphone
Overview Of Dynamic Microphone
• The moving coil microphones uses the principle of the
electromagnetic induction.
• when a coil is laced in the magnetic field is moved with
the sound pressure variations, there is change in the
magnetic flux through the coil.
• Microphone consists of the permanent magnet, a
diaphragm and a coil. The mass of the diaphragm is
negligible.
• Sound pressure varies, the diaphragm moves in response
to the changing force applied by the moving air.
 Principle Working:• sound moves the cone and the attached coil of wire moves in the field
of a magnet. The generator produces a voltage which "images"
the sound pressure variation - characterized as a pressure microphone.
Characteristics Of Dynamic Microphone
Frequency Response
200-5000 hz
Directivity
Omni directional
Resonant Frequency
3 to 4 KHz
Sensitivity
0.1 Pascal
Distance Of Speakers
25 to 30 cm
Distortion
5%
 Advantages Of Dynamic Microphone:•
•
•
•
They are robust inexpensive and resistant to the moisture.
Ideal for the on stage use.
Good for line vocals, which improves speech intelligibility.
Used for capacitor speaker cabinets and drum kits.
 Disadvantages Of Dynamic Microphone:• Does not respond linearly to all the audio frequency.
• Combining the multiple signals correctly is difficult and design
that do this are rare and tend to be expensive.
Condenser Microphone
Overview Of Condenser Microphone
• Sometimes called capacitor microphone.
• 2 parts: conductive diaphragm and metal back plate,
spaced very close together
• Both charged with static electricity
• When sound waves strike diaphragm, it vibrates,
varying the spacing between the plates
• This variation generates a similar signal to incoming
sound wave
• Diaphragm mass is lower, responds faster to rapidly
changing sound waves (transients)
 Principle Working:• sound pressure changes the spacing between a thin metallic
membrane and the stationary back plate. The plates are
charged to a total charge q.
Characteristics Of Condenser Microphone
Impedance
600 to 10,000 ohms
Directivity
Omni-directional
Distortion
<1%
Sensitivity
0.1 Pascal
Frequency Response
500 to 1100 Hz
Resonant Frequency
2 to 5 KHz
 Advantages Of Condenser Microphone:• When the ultra thin diaphragm response to the sound
pressure level, it changes the static electricity between the
conductors into electric signal directly.
• Due to the material of the diaphragm is very thin and light, and can
transform the sound into electric signal directly; the range of the
frequency response can reach to the ultra-low frequency.
• The diaphragm of the electret condenser microphone works without
any load.
 Disadvantages Of Condenser Microphone:• They are Expensive.
• May pop and crack when close mic.
• Requires a battery or external power supply to bias the plates.
Ribbon Microphone
Overview Of Ribbon Microphone
• A thin ribbon is placed in the magnetic field, it moves
at right angle to the magnetic field due to the sound
pressure.
• This produces change in the magnetic flux through
the ribbon conductor, inducing an emf across the
conductor.
• The ribbon microphone is call as the pressure
gradient microphone because the driving mechanical
force is proportional to the difference of the pressure
acting on the two sides of the conductor.
 Principle Working:• The air movement associated with the sound moves the
metallic ribbon in the magnetic field, generating an imagining
voltage between the ends of the ribbon which is proportional to
the velocity of the ribbon - characterized as a "velocity"
microphone.
Characteristics OF the Ribbon Microphone
Frequency Response
20 to 12000 hz
Directivity
Bidirectional
Impedance
0.25 ohm
Sensitivity
0.1 Pascal
Distortion
<1 %
Signal To Noise Ratio(SNR)
50 db.
 Advantages Of ribbon Microphone:•
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•
•
Good response for musical instrument.
Ideal for dramas.
Does not require an external bias.
Ideal for stereo recording.
 Disadvantages Of Ribbon Microphone:-
• It is very fragile and dielectric.
• Continuity and the resistance of the ribbon cannot be measured using
metallic.
• Any mechanical shock can displace the ribbon.
Microphone Selection Criteria
Natural, smooth tone quality
Flat frequency response
Bright, present tone quality
Presence peak (5kHz)
Extended lows
Omni condenser dynamic with extended low
frequency response.
Extended highs
condenser
Reduced leakage, reduced room acoustics
Directional
Coincident or near-coincident
Stereo mic
Extra ruggedness
Dynamic
Distortion-free pick-up of loud sounds
Condenser with high SPL spec or dynamic
Low self-noise, high sensitivity, noise-free
pickup of quiet sounds
Large-diaphragm condenser mic
Thank You