This document discusses different types of microphones and microphone techniques. It begins by explaining how microphones work as transducers that convert acoustic energy into electrical energy. It then describes various microphone types including condenser, dynamic, piezoelectric, ribbon, and carbon microphones. It also covers microphone polar patterns and placement techniques for mono and stereo miking. Key stereo miking techniques discussed include XY, ORTF, mid-side, and the Decca tree.

1. Microphones and Miking
Techniques

2. • A microphone is a transducer, in that it converts acoustic
energy (variations in air pressure) first into mechanical
energy (movement of diaphragm), and then into
electrical energy.
• Because microphones are concerned with electrical
power and sound waves, they are appropriately called
electro-acoustic transducers.

3. Condenser Microphones
• Condenser microphones operate on an electrostatic principle
• Microphones using the variable capacitor principle are universally
referred to in the industry as condenser microphones.
• A capacitor is an electrical device that is capable of storing
electrical charges
• A capacitor is an electrical device that is capable of storing
electrical charges
• The amount of charge that a capacitor can store is determined
by its value of capacitance and the applied voltage across its
plates according to the formula Q=CV
• Where
– Q is the charge in Coulombs
– C is the capacitance in Farads V is the voltage in Volts

4. • The capacitance of the capsule is determined by the
composition of the surface area of the plates (which are
fixed values), the dielectric or substance between the
plates (which in this case is air and is fixed), and the
distance between the plates (which is a variable).
• As the diaphragm (moving plate) vibrates as a result of
variation in air pressure, the distance between it and the
other plate of the capacitor varies and so does the
device’s capacitance. When the distance between the
plates decreases, the capacitance increases.

5. • The main disadvantage of a condenser microphone is
that it needs to be powered.
• It is unsuitable for use in live sound reinforcement due to
its overly sensitive response picks up leakage from
across the stage.
• limits its usage to a controlled acoustic environment such
as a studio is its excellent sensitivity to even small
pressure variations allowing it to capture the ambience
as well as other tiny details of sound in a musical
performance.

6. Dynamic microphone
• The dynamic microphone is one of the most widely used
types. It is also referred to as the moving coil
microphone.
• the dynamic pickup system operates by electromagnetic
induction in order to generate an output signal.
• When an electrically conductive metal is made to cut
across the flux lines of a magnetic field, a current of
specific magnitude and direction is generated withing
that metal.

7. • The motion of the coil in the fixed magnetic field in the
gap causes the wires of the voice coil to cut across the
flux in the gap. This in turn produces an induced current
across the coil that is analogous to the pressure
acting on the diaphragm.
• The output would be an electrical equivalent of the
acoustic sound wave hitting the diaphragm.
• The signal from the dynamic element can be used
directly, without the need for additional circuitry. This
design is extremely rugged, has good sensitivity when
close to the sound source and can handle the loudest
possible sound pressure levels without distortion

8. Peizo Electric Microphones
• Piezo means pressure, and hence piezo electric
translated means pressure electric.
• If pressure is applied to some crystalline substances
such as Rochelle salts, quartz, and man-made ceramics
like Barium Titanate, a voltage potential appears across
the faces of the crystal or ceramic.
• When the wafer or crystal is bent or twisted at an audio
frequency rate, the wave shape of the voltage generated
across the faces of the crystal will be the same as that of
the audio signal.

10. Ribbon Microphones
• In contrast to the moving-coil design, some dynamic
microphones use a metallic membrane, which functions
as both the diaphragm and as the moving conductor.
• Electrically conductive ribbon placed between the poles
of a magnet to produce a voltage by electromagnetic
induction.
• Extremely low mass of a ribbon diaphragm does offer a
potentially excellent transient response.

11. Microphone Polar Patterns
• An important
characteristic of a
microphone is its
response to sound
arriving from different
directions. This is also
called polar pattern.

12. • Omni directional Mics : The omni directional microphone
has equal response at all angles. Its “coverage” or pickup angle
is a full 360 degrees. This type of microphone can be used if
more room ambience is desired. For example, when using an
“omni”, the balance of direct and ambient sound depends on the
distance of the microphone from the instrument, and can be
adjusted to the desired effect.

13. Carbon Granule Microphones
• Carbon granules are loosely packed in contact with the
diaphragm in such a way that when the diaphragm
moves it moves the granules.
• This movement of the granules causes the closely
packed and less closely packed which affects the
resistance of the granules and therefore a DC current
flowing through he granules will be modulated.

14. Pressure Gradient Operation
• Bidirectional Microphones
• Unidirectional Type Microphone

15. • Cardioid : This has full sensitivity at 0 degrees (on-
axis) and is least sensitive at 180 degrees (off-axis).
• Supercardioid : front pickup angle115 and is least
sensitive direction is at 125 degrees.
• Hypercardioid : front pickup angle 105 and is least
sensitive direction is at 110 degrees.

16. • Microphone Placement is broken down into 2 broad
categories:
1. Mono miking
2. Stereo miking

17. In the study of acoustics there are three basic ways in
which sound is altered by its environment.
1. Reflection
2. Refraction
3. Diffraction
Reflection :
• Echo
• Reverberation
• Standing waves

18. Mono Microphone Techniques
• Distant Microphone Placement
• Close Microphone Placement
• Accent Miking
• Ambient Miking

19. • “3 ft or more” away from source. (often further)
• Captures direct and reflected sound
• Pro’s
– Useful for picking up an ensemble
– Natural tonal balance (at distance roughly equal to
size of sound source)
– Capture’s room acoustics naturally.
• Con’s
– Room acoustics must be good
– Phase cancellation can be a problem
Distant Microphone Placement

20. Close Microphone PlacementClose Microphone Placement
• 1 inch to 3 feet
• “present” sound quality
• Excludes acoustic environment (isolation)
• Tonal balance can be a problem
– Instruments don’t radiate all frequencies in all
directions
• Leakage should be avoided
– Physical distance between sources
– Directional microphones
– Gobo (acoustic barrier)

21. Accent MikingAccent Miking
• A not too close miking technique used to highlight an
instrument in an ensemble which is being picked by
distant mikes.
• The accent mike will add more volume and presence to
the highlighted instrument when mixed together with the
main mic.

22. Ambient Microphone PlacementAmbient Microphone Placement
• Large distance from source - reverberant signal more
prominent than direct.
• Control over natural reverb level in stereo or surround
applications
• Audience reaction
• Natural room acoustics

23. Stereo Miking TechniquesStereo Miking Techniques
• The use of two (or more) microphones to obtain a
coherent stereo image.
• Five main techniques:
– Spaced Pair
– X/Y
– ORTF
– M/S
– Decca tree

24. AB or Spaced PairAB or Spaced Pair
• Two mic’s (same make and model), placed in front of an
instrument/ensemble.
• Spacing ranges from a couple of feet to over 30 feet.
• Typically, omni pickup pattern is used.
• Interaural time and interaural amplitude cues create stereo
image.
• Potential for phase problems, especially when mixed to mono.
• In placing AB mics use the 3:1 Rule : the distance between the
to mics should be at least 3 times the distance between the mics
and the source.

25. X/YX/Y
• Two directional microphones (same make and model)
placed as close together as possible without touching.
(coincident technique)
• Generally at angle of 90° to 135°.
• Midpoint faces towards middle of source.
• Directionally comes entirely from amplitude differences.
• No phase problems.
• Cardiod or bi-directional
• Bidirectional gives the “Blumlein” pattern, which can yield
excellent ambient results.

26. ORTF
(Office for Radio and TV of France)
• Near coincident technique.
• Two directional microphones (same…), symmetrically
angled outwards at 110°, about 17 cm apart.
– simulates physical ear placement
• Combines directional amplitude differences and
interaural arrival time differences.
• Best when used at a distance from ensemble.
• Named after French National Broadcasting Organization.
(Office of Radiodiffusion—Television Française)

27. NOS stereo
• Two directional microphones (same…), symmetrically
angled outwards at 110°, about 17 cm apart.
• The NOS stereo technique is more useful at shorter
distances, for example on piano, small ensembles or
used for creating stereo on a instrument section in a
classical orchestra.

28. Mid-side technique
• Mid-side technique, using a cardiod pattern pointed at the sound
source, and a bi-directional microphone oriented towards the
sides (90° and 270°)
• The mid pickup captures the source, while the side pickup
captures ambience.
• Offers excellent control of source-to-ambient balance, even after
recording.
• Excellent source pickup for chamber music.
• No phase problems when mixed to mono. (coincident)
• Requires a decoder/transformer matrix:
– Software decoder, or
– The side pickup is sent to two channels, with the phase
reversed on one channel.
– M + S = X ; M - S = Y