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microphone theory
microphone theory
138
Music
Undergraduate 1
08/06/2012

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Term
what does the Greek 'micro' and 'phon' stand for
Definition
"small sound"
Term
who coined the name microphone
Definition
Wheatstone
Term
what are microphones
Definition
transducers
Term
what does a transducer do
Definition
convert acoustic energy into electrical energy
Term
another name for carbon mics
Definition
resistance mics
Term
make-up of a carbon mic
Definition
contain a section filled with carbon granules and the vibration of the diaphragm
Term
packing
Definition
the vibration of the diaphragm of a carbon mic causes teh granules to be compressed over time
Term
what were carbon mics used for
Definition
military applications and telephone handsets
Term
what does piezin stand for
Definition
to compress
Term
who discovered the Piezoelectric effect
Definition
Pierre Curie
Term
how do Ceramic/Crystal miss operate
Definition
the Piezoelectric effect
Term
Piezoelectric materials
Definition
quartz, tourmaline, Rochelle salt, cane sugar, barium titanate
Term
can you apply Phantom Power to a crystal mic
Definition
no
Term
what mics use Piezoelectric materials
Definition
underwater mics
Term
what principle operates Magnetic/dynamic/ribbon mics
Definition
Magnetic Induction
Term
FaraDays Law of Magnetic Induction
Definition
e=Blv
Term
what does the 'e' of e=Blv stand for?
Definition
electromotive force in volts
Term
what does the 'B' of e=Blv stand for?
Definition
magnetic field strength
Term
what does the 'l' of e=Blv stand for?
Definition
length of the conductor
Term
what does the 'v' of e=Blv stand for?
Definition
velocity of the conductor moving through the magnetic field
Term
what is the combination of ribbon and magnets considered
Definition
a motor
Term
what will doubling ribbon length do
Definition
yield a 6dB increase in output, but causes a loss of high frequency
Term
can you use Phantom Power with a Ribbon mic
Definition
NO
Term
how thick is a ribbon in a ribbon mic
Definition
3-6 microns
Term
another name for condenser mics
Definition
Capacitor mics
Term
who developed condencer mics
Definition
E.C. Wente in bell labs
Term
who first mass produced condencer mics
Definition
Neumann
Term
before placing a mic on a stand ensure:
Definition
the boom is extended over a leg
body screwed into boom tightly
Term
how to store mics with magnetic structures
Definition
in their protective felt bags
Term
types of transducers
Definition
carbon
ceramic/crystal
magnetic/dynamic
ribbon
condeser
Term
the size of carbon granules in carbon mics
Definition
approximately 100 microns
Term
how to fix packing problem in carbon mics
Definition
gently rap against a hard surface
Term
what does piezein stand for
Definition
to press
Term
when was the Piezoelectric effect discovered
Definition
1880 in quartz crystals
Term
what is the piezoelectric effect
Definition
an electrical voltage is created when the piezoelectric material is subjected to mechanical stress
Term
how does a crystal mic operate
Definition
sound waves hitting the diaphragm put pressure on the piezoelectric material causing a voltage
Term
type of transducer found in acoustic guitar pickups
Definition
crystal and ceramic mics
Term
Another name Magnetic-Dynamic Microphones
Definition
electrodynamic or electromagnetic mics
Term
how do magnetic-dynamic mics operate
Definition
the principles of magnetic induction
Term
who discovered magnetic induction
Definition
Michael Faraday in 1831
Term
Faraday's Law of Magnetic induction states....
Definition
moving a conductor (coil of wire) through a magnetic field will cause a voltage to be induced across the conductor
Term
amount of voltage induced in magnetic induction is proportional to...
Definition
magnetic field strength
length of the conductor
velocity of conductor moving through the magnetic field
Term
shape of modern dynamic mics
Definition
dome shaped
Term
what are dynamic mic diaphragms usually made of
Definition
plastic or coated with aluminum
Term
what is a voice coil
Definition
coil of wire wrapped around the dome
Term
sensitivity of dynamic mics
Definition
less responsive to transient frequencies due to the size of the diaphragm
Term
SPL spec of the AKG D112
Definition
outside measurement range
Term
size of the ribbon in ribbon mics
Definition
3-6 microns
Term
sensitivity of the ribbon mic determined by:
Definition
ribbon thickness
corrugations per inch
tensioning
Term
where is the ribbon of a ribbon mic suspended
Definition
between the poles of a strong magnet
Term
output of a ribbon mic dependent on:
Definition
conductor length
movement of the conductor in the magnetic field
magnetic field strength
Term
only practical means of increasing output voltage of a ribbon mic
Definition
increasing magnetic field strength
Term
transient response of a ribbon mic
Definition
excellent
Term
weight of the RCA 44BX
Definition
8.5lbs (due to size of magnet)
Term
Roswellite
Definition
a nano-enabled material or acoustic nano-film that makes the ribbon extremely strong
Term
who developed Roswellite
Definition
Soundwave Research Laboratories
Term
how does a condenser mic operate
Definition
two parallel metal plates, each holding an opposing charge, creates a capacitor
sound hits the diaphragm changing the distance causing change in capacitance
sent to a circuit taht translates this change into an electrical signal that is analoguous to the sound wave
Term
what are the two metal plates of a condenser mic
Definition
the diaphragm and the backplate
Term
what is the diaphragm in a condenser mic made of
Definition
thin piece of metal or plastic, such as Mylar, coated with gold or nickel
Term
thickness of the diaphragm in a condenser mic
Definition
.5-10 microns
Term
how is the backplate of a condenser mic constructed
Definition
usually made of milled brass with a number of holes drilled into it
Term
what are the holes in the diaphragm of a condenser mic for
Definition
provide damping, acting as a spring of sorts
Term
what does a condenser mic require
Definition
a preamplifier
Term
what can the preamp of a condenser mic be
Definition
a tube or solid state
Term
how does an electret condenser mic make capacitance
Definition
permanent static electric charge
Term
what is power from battery or phantom used for in an electret condenser mic
Definition
power the mics internal pre-amp
Term
what is used to power a condenser mic
Definition
external power supply unit (PSU)
phantom power
battery
Term
what are the 3 voltages for phantom power
Definition
12
24
48
Term
what does the basket of a condenser mic do
Definition
protect the capsule from physical damage
protect from stray RFI
Term
microphone polar pattern
Definition
a plot that describes the sensitivity of a mic to sounds arriving from any direction over a 360 degree range
Term
on-axis
Definition
sounds that arrive at the 0 degree position relative to the mic capsule
Term
two types of addresses
Definition
end and side
Term
off axis
Definition
sound that arrive from angels other than the 0 degree position relative to the mic capsule
Term
omnidirectional
Definition
equal sensitivity to sounds from all directions
Term
bidirectional
Definition
sensitive to sounds arriving from the front and rear
Term
pure polar patterns
Definition
pressure microphone: omni
pressure gradient: bidirectional
Term
pressure microphone
Definition
omnidirectional
Term
pressure gradient
Definition
bidirectional
Term
Altec/Western Electric 639
Definition
has both a ribbon and a diaphragm
Term
types of polar patterns
Definition
figure 8 (bi)
Super-Cardioid
Hyper-Cardioid
Cardioid
Sub-Cardioid
Omnidirectional
Term
how polar patterns are created electrically in condensers
Definition
a pair of cardioid capsules are mounted back-to-back
(outputs are combined to create other polar patterns)
Term
creating omni pattern electrically
Definition
equal amount + from each cardioid capsule
Term
creating bidirectional pattern electrically
Definition
equal amount + from one and - from the other
Term
creating cardioid electrically
Definition
+ from only one
Term
creating super/hyper cardioid patterns electrically
Definition
more + from one and less - from the other
Term
creating sub cardioid electrically
Definition
more + from one and less + from the other
Term
Proximity effect
Definition
as the distance from the source decreases, microphones with directional polar patterns will exhibit an increase in low frequency response
Term
amount of dB increase in Shure 57 at 100 Hz when placed 1/4" from the sound source
Definition
6-10dB
Term
Omni directional
Definition
has extended low frequency pickup
less proximity effect than directional mics
Term
bidirectional
Definition
pattern usually very even except at highest freqs
more proximity effect than cardioid or hyper-cardioid
Term
cardioid
Definition
most sensitive to sounds arriving from the front while rejecting sounds from the rear
Term
super-cardioid
Definition
sensitive in a slightly narrower pattern in the front than a cardioid and has a small lobe at the rear
Term
hyper-cardioid
Definition
sensitive in a narrower pattern in the front than a cardioid and has a prominent lobe at rear
Term
shotgun
Definition
extremely narrow area of sensitivity in front with extended "reach" also has multiple lobes which vary in position with frequency
Term
how is the shotgun pattern created
Definition
using an interference tube
Term
coverage angle of omni
Definition
360 degrees
Term
coverage angle of cardioid
Definition
131 degrees
Term
coverage angle of supercardioid
Definition
115 degrees
Term
coverage angle of hypercardioid
Definition
105 degrees
Term
coverage angle of bidirectional
Definition
90 degrees
Term
angle of max rejection in cardioid
Definition
180 deg
Term
angle of max rejection in supercardioid
Definition
126 deg
Term
angle of max rejection in hypercardioid
Definition
110 deg
Term
angle of max rejection in bidirectional
Definition
90 deg
Term
rear sensitivity (relative to front) of onmi
Definition
0
Term
rear sensitivity (relative to front) of supercardioid
Definition
12dB
Term
rear sensitivity (relative to front) of hypercardioid
Definition
6dB
Term
rear sensitivity (relative to front) of bidirectional
Definition
0
Term
ambient sound sensitivity of omni
Definition
100%
Term
ambient sound sensitivity of cardioid
Definition
33%
Term
ambient sound sensitivity of supercardioid
Definition
27%
Term
ambient sound sensitivity of hypercardioid
Definition
25%
Term
ambient sound sensitivity of bidirectional
Definition
33%
Term
distance factor of omni
Definition
1
Term
distance factor of cardioid
Definition
1.7
Term
distance factor of supercardioid
Definition
1.9
Term
distance factor of hypercardioid
Definition
2
Term
distance factor of bidirectional
Definition
1.7
Term
distance factor of sub-cardioid
Definition
1.3
Term
mic specs
noise
Definition
level of self-noise
Term
mic specs
max SPL
Definition
max level possible with a certain amount of measured distortion
Term
mic specs
dynamic range
Definition
total dynamic range of the mics internal pre-amp
Term
mic specs
sensitivity
Definition
measured in millivolts per Pascal
Term
sound pressure
Definition
pressure and pressure variations are expressed in Pascals (Pa) or N/m2
Term
Newton
Definition
equal to about .2248lbs
Term
Sound Pressure Levels
Definition
comparing sound pressure levels in decibels to pascals
Term
SPL devices
Definition
Real Time Analyzers
FFT analyzers
Term
FFT Analyzers
Definition
SIA SMAART
Meyer SIM
Term
Handheld SPL meter
Definition
used to maintain safe working conditions
used to prevent violation of sound level and noise pollution laws
Term
calibration devices
Definition
Pistonphone calibrator
Term
what is generated commonly by calibration devices
Definition
94 dB SPL @ 1Khz
Term
what is less commonly generated by calibration devices
Definition
124 dB SPL @ 250 hz
Term
Phase Ports
Definition
allow sound to reach the rear of the capsule/diaphragm, to create cardioid, super cardioid, and hyper cardioid patterns
Term
what is a Pascal
Definition
equal to 94 dB SPL
Term
A-weighting
Definition
measurement similar to how our hearing works
Term
C-weighting
Definition
measurement close to overall sound level
Term
measurement mics
Definition
small diaphragm electret condensers, extremely flat frequency response omnidirectional pattern
Term
used to calibrate sound pressure measurement devices
Definition
Pistonphone
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