what does the Greek ‘micro’ and ‘phon’ stand for
“small sound”
who coined the name microphone
what are microphones
what does a transducer do
convert acoustic energy into electrical energy
another name for carbon mics
resistance mics
make-up of a carbon mic
contain a section filled with carbon granules and the vibration of the diaphragm
the vibration of the diaphragm of a carbon mic causes teh granules to be compressed over time
what were carbon mics used for
military applications and telephone handsets
what does piezin stand for
to compress
who discovered the Piezoelectric effect
Pierre Curie
how do Ceramic/Crystal miss operate
the Piezoelectric effect
Piezoelectric materials
quartz, tourmaline, Rochelle salt, cane sugar, barium titanate
can you apply Phantom Power to a crystal mic
what mics use Piezoelectric materials
underwater mics
what principle operates Magnetic/dynamic/ribbon mics
Magnetic Induction
FaraDays Law of Magnetic Induction
what does the ‘e’ of e=Blv stand for?
electromotive force in volts
what does the ‘B’ of e=Blv stand for?
magnetic field strength
what does the ‘l’ of e=Blv stand for?
length of the conductor
what does the ‘v’ of e=Blv stand for?
velocity of the conductor moving through the magnetic field
what is the combination of ribbon and magnets considered
a motor
what will doubling ribbon length do
yield a 6dB increase in output, but causes a loss of high frequency
can you use Phantom Power with a Ribbon mic
how thick is a ribbon in a ribbon mic
3-6 microns
another name for condenser mics
Capacitor mics
who developed condencer mics
E.C. Wente in bell labs
who first mass produced condencer mics
before placing a mic on a stand ensure:
the boom is extended over a leg
body screwed into boom tightly
how to store mics with magnetic structures
in their protective felt bags
types of transducers
the size of carbon granules in carbon mics
approximately 100 microns
how to fix packing problem in carbon mics
gently rap against a hard surface
what does piezein stand for
to press
when was the Piezoelectric effect discovered
1880 in quartz crystals
what is the piezoelectric effect
an electrical voltage is created when the piezoelectric material is subjected to mechanical stress
how does a crystal mic operate
sound waves hitting the diaphragm put pressure on the piezoelectric material causing a voltage
type of transducer found in acoustic guitar pickups
crystal and ceramic mics
Another name Magnetic-Dynamic Microphones
electrodynamic or electromagnetic mics
how do magnetic-dynamic mics operate
the principles of magnetic induction
who discovered magnetic induction
Michael Faraday in 1831
Faraday’s Law of Magnetic induction states….
moving a conductor (coil of wire) through a magnetic field will cause a voltage to be induced across the conductor
amount of voltage induced in magnetic induction is proportional to…
magnetic field strength
length of the conductor
velocity of conductor moving through the magnetic field
shape of modern dynamic mics
dome shaped
what are dynamic mic diaphragms usually made of
plastic or coated with aluminum
what is a voice coil
coil of wire wrapped around the dome
sensitivity of dynamic mics
less responsive to transient frequencies due to the size of the diaphragm
SPL spec of the AKG D112
outside measurement range
size of the ribbon in ribbon mics
3-6 microns
sensitivity of the ribbon mic determined by:
ribbon thickness
corrugations per inch
where is the ribbon of a ribbon mic suspended
between the poles of a strong magnet
output of a ribbon mic dependent on:
conductor length
movement of the conductor in the magnetic field
magnetic field strength
only practical means of increasing output voltage of a ribbon mic
increasing magnetic field strength
transient response of a ribbon mic
weight of the RCA 44BX
8.5lbs (due to size of magnet)
a nano-enabled material or acoustic nano-film that makes the ribbon extremely strong
who developed Roswellite
Soundwave Research Laboratories
how does a condenser mic operate
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
what are the two metal plates of a condenser mic
the diaphragm and the backplate
what is the diaphragm in a condenser mic made of
thin piece of metal or plastic, such as Mylar, coated with gold or nickel
thickness of the diaphragm in a condenser mic
.5-10 microns
how is the backplate of a condenser mic constructed
usually made of milled brass with a number of holes drilled into it
what are the holes in the diaphragm of a condenser mic for
provide damping, acting as a spring of sorts
what does a condenser mic require
a preamplifier
what can the preamp of a condenser mic be
a tube or solid state
how does an electret condenser mic make capacitance
permanent static electric charge
what is power from battery or phantom used for in an electret condenser mic
power the mics internal pre-amp
what is used to power a condenser mic
external power supply unit (PSU)
phantom power
what are the 3 voltages for phantom power
what does the basket of a condenser mic do
protect the capsule from physical damage
protect from stray RFI
microphone polar pattern
a plot that describes the sensitivity of a mic to sounds arriving from any direction over a 360 degree range
sounds that arrive at the 0 degree position relative to the mic capsule
two types of addresses
end and side
off axis
sound that arrive from angels other than the 0 degree position relative to the mic capsule
equal sensitivity to sounds from all directions
sensitive to sounds arriving from the front and rear
pure polar patterns
pressure microphone: omni
pressure gradient: bidirectional
pressure microphone
pressure gradient
Altec/Western Electric 639
has both a ribbon and a diaphragm
types of polar patterns
figure 8 (bi)
how polar patterns are created electrically in condensers
a pair of cardioid capsules are mounted back-to-back
(outputs are combined to create other polar patterns)
creating omni pattern electrically
equal amount + from each cardioid capsule
creating bidirectional pattern electrically
equal amount + from one and – from the other
creating cardioid electrically
+ from only one
creating super/hyper cardioid patterns electrically
more + from one and less – from the other
creating sub cardioid electrically
more + from one and less + from the other
Proximity effect
as the distance from the source decreases, microphones with directional polar patterns will exhibit an increase in low frequency response
amount of dB increase in Shure 57 at 100 Hz when placed 1/4″ from the sound source
Omni directional
has extended low frequency pickup
less proximity effect than directional mics
pattern usually very even except at highest freqs
more proximity effect than cardioid or hyper-cardioid
most sensitive to sounds arriving from the front while rejecting sounds from the rear
sensitive in a slightly narrower pattern in the front than a cardioid and has a small lobe at the rear
sensitive in a narrower pattern in the front than a cardioid and has a prominent lobe at rear
extremely narrow area of sensitivity in front with extended “reach” also has multiple lobes which vary in position with frequency
how is the shotgun pattern created
using an interference tube
coverage angle of omni
360 degrees
coverage angle of cardioid
131 degrees
coverage angle of supercardioid
115 degrees
coverage angle of hypercardioid
105 degrees
coverage angle of bidirectional
90 degrees
angle of max rejection in cardioid
180 deg
angle of max rejection in supercardioid
126 deg
angle of max rejection in hypercardioid
110 deg
angle of max rejection in bidirectional
90 deg
rear sensitivity (relative to front) of onmi
rear sensitivity (relative to front) of supercardioid
rear sensitivity (relative to front) of hypercardioid
rear sensitivity (relative to front) of bidirectional
ambient sound sensitivity of omni
ambient sound sensitivity of cardioid
ambient sound sensitivity of supercardioid
ambient sound sensitivity of hypercardioid
ambient sound sensitivity of bidirectional
distance factor of omni
distance factor of cardioid
distance factor of supercardioid
distance factor of hypercardioid
distance factor of bidirectional
distance factor of sub-cardioid
mic specs
level of self-noise
mic specs
max SPL
max level possible with a certain amount of measured distortion
mic specs
dynamic range
total dynamic range of the mics internal pre-amp
mic specs
measured in millivolts per Pascal
sound pressure
pressure and pressure variations are expressed in Pascals (Pa) or N/m2
equal to about .2248lbs
Sound Pressure Levels
comparing sound pressure levels in decibels to pascals
SPL devices
Real Time Analyzers
FFT analyzers
FFT Analyzers
Meyer SIM
Handheld SPL meter
used to maintain safe working conditions
used to prevent violation of sound level and noise pollution laws
calibration devices
Pistonphone calibrator
what is generated commonly by calibration devices
94 dB SPL @ 1Khz
what is less commonly generated by calibration devices
124 dB SPL @ 250 hz
Phase Ports
allow sound to reach the rear of the capsule/diaphragm, to create cardioid, super cardioid, and hyper cardioid patterns
what is a Pascal
equal to 94 dB SPL
measurement similar to how our hearing works
measurement close to overall sound level
measurement mics
small diaphragm electret condensers, extremely flat frequency response omnidirectional pattern
used to calibrate sound pressure measurement devices