Microphones - Pro Audio Systems

Transcription

Microphones
Selection & Application…
Ryan Thomas - Audio-Technica
Rthomas@audio-technica.co.uk
© 2007 Audio-Technica
What is a Microphone
Transducer —
Converts one form of energy to another
• Loudspeaker:
Converts electrical energy
to acoustic energy
• Microphone:
Converts acoustic energy
to electrical energy
Decibel
The unit used to measure the intensity of a sound
–
–
–
–
Relationship between two values of power
The two numbers are of greatly different magnitude
Based on the Logarithmic scale
Useful due to the way an ear perceives loudness
Key Decibel facts:
–
–
–
Doubling the power = increase of 3 dB
Halving the power = decrease of 3 dB
Ten times (10 x) the power = increase of 10 dB
Frequency Range
The Human Voice:
–
–
–
Voice range: Approximately 100Hz - 6kHz
80 percent of voice energy: Below 500Hz
“Presence” range: Between 2kHz and 5kHz
Signal, Noise, Feedback
Signal to Noise
Signal is the desired sound source.
Noise is everything else.
Acoustical Feedback
Feedback occurs when SPL of amplified sound at
the microphone is equal to or greater than that of
the original source sound.
Frequency Response
Output measurement showing the accuracy with which a device reproduces
the relative amplitudes of all frequencies presented to its input
-
Wider (low to high) is better
Flatter is better
Some microphones have filters to “roll-off ”
low end response to reduce noise pickup
Proximity Effect
Boost in low frequency response as one moves closer to a microphone
-
More common in Dynamic microphones
More common in directional models
Sound Pressure Levels
45 ACP Colt Pistol (25 Feet)
50 HP Siren (100 Feet)
Threshold of Pain
Typical Studio
Monitors for:
Rock Music (10 Feet)
Loud Gospel Music
Heavy Street Traffic (5 Feet)
Average Conversation (3 Feet)
Average Suburban Home (Night)
Quiet Auditorium
Quiet Recording Studio
Quiet Whisper (5 feet)
Threshold of Hearing
(Youths, 1 kHz to 4 kHz)
Maximum SPL
•
•
•
•
Loudest sound before distortion
Expressed in Decibels (dB)
Larger value is better
Dynamic mics typically handle higher SPL levels
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Dynamic Microphones
–
–
–
–
–
–
–
Rugged construction, robust,
able to take much abuse
Large physical size
Requires no external power
High SPL (Sound Pressure Level) capacity
Miniaturization results in compromises
Response limits due to mechanical aspects
Hand held vocals, paging, communication
Ribbon Microphones
–
–
–
–
–
–
–
–
Classic broadcast mics
Large physical size, heavy
Requires no external power
Warm rich sound, wide response
Can be very fragile
Can not handle wind or blowing
Can be damaged by phantom power
Voice over, vocals
Condenser Microphones
–
–
–
–
–
–
–
May have extended response
Handles transients very well
High sensitivity, lower handling noise
Less weight, easy to miniaturize
Require external power to operate
(battery or “phantom”)
Rugged construction of newer models
Can be sensitive to heat and humidity
Directional Characteristics
0º
–
Omnidirectional microphones pick up
sound equally from all directions
90º
180º
–
Directional microphones favor a specific
direction often associated with mic’s axis
–
–
0º
Favored direction is On-Axis
Other directions are Off-Axis
90º
180
º
Polar Patterns
–
–
Represent direction of sound pickup
On-Axis vs. Off-Axis:
–
–
On-Axis is the 0° position in the pattern
Polar pattern types:
–
–
–
–
–
–
Omni directional
Cardioid
Supercardioid
Hypercardioid
Line Gradient (Shotgun)
Bi-directional (Figure 8)
Microphones – Angles…
Acceptance Angle
–
–
–
A measurement of the optimum angle of coverage
in which a microphone will pickup sounds
Outside the acceptance angle audio level and
performance will drop off steeply
Acceptance angle is determined by the microphones
polar pattern and physical design
Null Angle
–
–
–
A measurement of the point in a directional
pattern microphone where maximum
sound rejection occurs
In relation to the front of the microphone
or on-axis position
This point is key to minimizing the effects
of acoustical feedback when using
microphones with monitor speakers in live situations
Cardioid's Angles
Cardioid Acceptance Angle
–
–
131 degrees for typical cardioid
Classic "heart-shaped" pattern
Cardioid Null Angle
–
–
180 degrees for typical cardioid
Ideal for use with monitor speakers to
control/minimize feedback.
Hypercardioid's Angles
Hypercardioid Acceptance Angle
–
–
105 degrees typical
Small rear lobe pick up
Hypercardioid Null Angle
–
–
110 degrees typical
Do not place monitor speaker
directly behind mic as lobe
can cause feedback
Acoustic Phase Interference
•
•
•
Interaction between two microphones & same sound source
Based on distance between mics and talker
Sometimes called “comb filtering”
• Also can be caused by reflections of sound
from tables and other surfaces or boundaries
• Solution:
- Place microphone closer to sound source
- Move microphone further from reflective source
- Use “boundary type” microphone
Boundary Microphone
• Microphone element is close to surface
• Direct and reflected sound
arrive at same time
• Polar Pattern is hemispherical
• Typically condenser microphones
Eliminating Feedback
Select Best Mic Type
Improve Signal to Noise Ratio
Signal is the desired sound source.
Noise is everything else.
Move mics closer to sound source
Dynamic
Condenser
Take Advantage of the “Angles”
Angles”
Use Inverse Square Law
Test… 1 - 2 - 3
For each doubling of distance
from the sound source, the
SPL will drop 6 dB.
Cardioid
Watch Number of “Open Mics”
Mics”
Use “offoff-axis”
axis” Response
A mic with good off-axis response will
not exhibit any frequency anomalies
that could be susceptible to feedback
Hypercardioid
–
–
–
Keep number of open (on)
microphones to a minimum
Good mixing skills count
Investigate automatic
(SmartMixer) mixers to
automatically control mics
Application – Mics on a Podium
• Talker: Person speaking or reading.
• Speaker: Loudspeaker, part of sound system
• Use only one microphone on a podium.
– Multiple mics can cause phase cancellation
due to varying distance between mics and talker.
– Multiple mics on TV podiums are often feeds to
different locations (Broadcast, recording, etc.)
• Condenser mics are more sensitive and
can be worked at a greater distance
• If more distance is required between mic
and talker,consider using a UniLine
miniature shotgun mic.
Microphones: U857 (Q or A mount series) – Best
Pro 47T or Pro 49Q – Better
Podium Mics and Wireless Users
• Use only one or the other, but not both at same time.
– Live wireless worn by talker can cause phase cancellation with mic on podium.
– Mute podium mic or have wireless user turn off the wireless transmitter
– UniMute remote mute switch can be controlled by wireless user.
• Also applies to communion table, altar, etc.
• Smart Mixer automatic mixer can be
configured so podium mic takes priority.
Application – Mics on Talkers
• Traditional lavalier (clip-on) mic.
– Cardioid pattern: minimizes feedback, but is susceptible to
proximity effect and sound can vary in level if talker moves
their head (animated talker).
– Omnidirectional pattern: more prone to feedback, but is less
susceptible to proximity effect and sound does not vary in
level if talker moves their head.
• Locate microphone on lapel one “thumbs-up” below mouth.
• Use “broadcast loop” to secure cable to minimize cable
noise pickup.
Microphones: AT899 (omnidirectional), AT898 (Cardioid) – Best
AT831 – Better
Pro70 – Good (Rugged dynamic)
• Subminiature headworn mic
– Typically omnidirectional pattern for smoother
response and no proximity effect
– Feedback less of an issue since mic is so close to
the talkers mouth
• Locate microphone capsule near edge of mouth
but not in front of mouth
• Use cable clip provided with the mic to minimize
mic movement when talker moves their head.
Microphones: AT892 Series – Best (wireless terminations)
ATM75 – Better
Pro 8HEx – Good (Rugged dynamic)
Application – Mics on a Choir
•
•
Suspend mics over choir or use movable “studio booms”
for portable applications or situations where the choir location on
platform changes.
Choir mic choices include:
–
–
–
•
•
Traditional miniature hanging
condenser cardioids or hypercardioids.
UniPoint U853R series
ProPoint Pro45 series
Large diaphragm compact live performance
condenser cardioids.
Artist Elite AE5100
Large diaphragm side address
studio condensers
AT4033, AT4050
Keep mics behind loudspeakers “plane” to minimize feedback
Use 3 to 1 rule
-
Space microphones 3 times the distance of a mic to the singers
I.e.: if mics are 3' from singers, they should be 9' apart
Application – Mics on a Choir
Cardioid Microphones – The Angles
–
s th
en
2
tim
e
s “X
”
“X
–
Les
ce
tan
Dis
–
131 degree angle picks up
more of the singers
Good for choirs with several narrow rows
of singers
Can be more susceptible
to acoustical feedback from
nearby speakers
”
131°Angle of
Acceptance
UniLine Microphones – The Angles
–
X”
90°Angle of
Acceptance
then
2 tim
es
“
ce
tan
–
Dis
–
Less
90 degree narrow angle of acceptance
picks up less of unwanted sounds
Good for choirs with several wide rows
of singers
Better choice when choir is using
monitor speakers for track playback
“X”
Hanging Choir Mics
UniPoint – U853 Series
•
Remove cable “factory twist”
–
–
•
Uncoil cable
Pull cable through thumb and finger to
eliminate twist
Use wire hanger to position
–
Turning capsule in hanger will help aim mic
Artist Elite – AE5100
•
•
Use Hanger Slug
Remove cable factory twist
–
–
•
Uncoil cable
Pull cable through thumb and finger to
eliminate twist
Attach cable to Hanger Slug with cable tie
–
Use mic clip to position and angle mic
Application – Mics on Thespians
• Mics on performers – hidden lavaliere
– Best location is at hairline, in center of forehead with
capsule facing downward.
– Omni or unidirectional mics will work.
– Wigs and hats are ideal locations to hide mic and
wireless body packs.
• Mics on performers – headworn mic
– Ideal for softer talkers
– Easy to move from performer to performer
(shared mics).
– Available in several colors (black, theatre beige,
cocoa).
– Clip cable to performer’s costume for security.
– Use “sweat bead” on mic boom to prevent perspiration
from getting into capsule.
• Spot Mics – in set pieces or hidden
– Use small shotgun mics to isolate performance areas.
– Wireless body pack can be mounted to set piece.
• Area Mics
– Use boundary mics across the front of
platform for general sound pickup.
– Remember 3-1 rule.
– Shotgun mics in fly space can be used to
cover upstage areas.
Microphones: AT4073, 4071 Shotguns - Best
AT897 Shotgun - Better
U853 UniLine – Alternative small shotgun
Application – Mics on the Piano
Grand Piano – Lid Open (full stick)
–
2 mics (Stereo pair, X-Y configuration) or spaced pair 12” above
strings about 6-8” from hammers.
• Gives wide expansive sound with less pickup of ambience
• Remember 3-1 rule for spacing
• Position closer to hammers for more “attack”
–
Single mic over sound board “sweet-spot”
–
Pair of mics aimed into sound holes
• Listen with one ear covered to find sweet spot
• Good isolation, but sound is thin and dull
• Use mid range and high Eq on channel for more natural sound.
Grand Piano – Lid Partially Open (short stick)
–
2 mics (Stereo pair, X-Y configuration) or spaced pair 6” above strings about 6-8” from hammers.
• Improved isolation, but sound may be muddy or boomy and lack attack.
• Remember 3-1 rule for spacing
• Use channel Eq to roll off bass and increase highs for more natural sound
–
Boundary mic mounted on underside of lid over lower treble strings.
• Closer to hammers provides brighter sound
Grand Piano – Lid Closed
–
2 boundary mics mounted to closed lid (at keyboard edge) Space about 2/3 distance from
middle “A” to each end of keyboard.
• Provides excellent isolation and bright well balanced sound
• Alternate is to mount mics on “Gaff tape bridge” on piano frame.
–
Single boundary mic mounted vertically on inside of frame at curved wall apex
• Full natural sound and excellent isolation. Can minimize hammer and damper noise.
Note: mic placed under piano aimed up at soundboard is unobtrusive, but sound can be
boomy bassy or dull sounding compared to other mic placement techniques.
Microphones: AE5100 or AT4051 – Best
ATM350 clip-on or ATM450 – Better
Pro37 – Good
AE2500 or ATM250 DE – Interesting
Boundary Microphones: U851R – Best (AT849 alternative)
Pro44 - Better
Application – Mics on the Piano
Upright Piano
–
1 mic 6” over open top placed above treble strings.
•
•
•
•
Gives a natural sound, but lacks bass.
Can pick up hammer attack.
Good placement for single mic.
Add second mic 6” over open top above bass strings
for slightly fuller sound
• Remember 3-1 rule.
–
Pair of mics aimed at the soundboard (6-8”)
•
•
•
•
•
–
Remember 3-1 rule
Will not pick up hammer attack.
Bass side: full sound but slightly tubby
Treble side: thin sound
Alternative is to use single mic on hard surface
(floor, or carpet plate) 12-15” from center of
sound board for a more natural sound. (Note: soundboard should be
facing into room and not against a wall.)
Boundary mic attached to inside of closed piano lid.
• Unobtrusive mic position
• Experiment with placement to balance between low and high strings.
ATM450 - Better
ATM350 clip-on – Better
Pro37 – Good
Boundary Microphones: U851R – Best (AT849 alternative)
Pro44 - Better
Electronic Keyboard
–
Use DI (Direct Injection Box) on output of keyboard or amplifier
• Keyboard’s amp is for player’s monitor.
–
If player desires amp to be miked…
Microphones: AE3000 – Best
ATM450 - Better
Application – Mics on the Guitar
Acoustic Guitar
–
As mic is moved around in front of the guitar, it captures
different balances between the various resonating parts
of the instrument.
• Often player will use this to affect his sound.
• Closer mic placement can yield an “unbalanced sound”
–
Single mic near sound hole (4-6”)
• Closer to hole gives a more boomy or bassy sound
(use Eq to correct).
• Closer to sound hole provides more isolation.
• Susceptible to pick and string noise
–
Single mic 4-6” from bridge
• Reduces pick and string noise
• Gives a warmer “woody” sound, lacks detail.
–
Single mic near neck (12’th fret)
• Captures more mellow tone
• Can pick up finger on string sounds.
–
Clip-on mic (use miniature lav style)
• Allow for freedom of movement by player without affecting
overall sound (can be connected to wireless system).
• Clipped outside of sound hole: provides natural well balanced
sound (slightly bright with detail).
• Clipped inside of sound hole: provides more bassy sound, but
less string noise.
Note: AT831R miniature unidirectional condenser microphone includes an AT8444 instrument
mount designed to attach the mic to an acoustic guitar.
ATM450 or AT3031 – Better
Pro37 – Good
Clip-on Microphone: U831R
Application – Mics on the Guitar
Electric Guitar (amplifier)
–
Close mic speaker cone.
• Traditionally done with dynamic directional mic.
• New condensers are capable of handling the high SPL
generated by the speaker.
–
Three main considerations:
• Distance: amount of space between the microphone and
the speaker (often the grille cloth)
• Position: where mic is located in relation to the circle
of the speaker cone
• Angle: direction the microphone is facing in relation
to the speaker cone
–
Distance
• 2” – 8” is typical
• Provides maximum sonic isolation from other instruments
and room sound
–
Position:
• Center provides brighter tone, susceptible to more amp hiss.
• Off –center, fuller sound (less bright) and less hiss
• Can pick up finger on string sounds.
–
Angle:
• Directly facing speaker (on-axis), brighter tone, more hiss
• As mic is angled more off-axis, the midrange tones increase
• Sometimes for quick setup, the mic is draped by it’s cable over the
amplifier cabinet and hangs 90 degrees off axis from the speaker.
Microphones: AE3000 – Best
ATM650 – Better
ATM250DE – Better (if 2 inputs available)
Pro 63 – Good
Alternate used by touring companies: AT4033
Application – Mics on Drums
Kick Drum
–
Right balance of: beater, head, shell resonance
• Closer to head – more beater, accentuates sharp attack
• Closer to center – accentuate lower frequencies
• Closer to sides – more harmonics
–
–
–
Inside drum, off center
Listen for sweet spot
Use tow mics or AE2500 (Dynamic for beater attack,
condenser for shell tone)
Drum with no hole – place mic close to head, listen for sweet
spot.
–
Microphones: AE2500 – Best (requires 2 input channels)
ATM250DE – Better (requires 2 input channels)
ATM250 – Better
Pro25 - Good (MB 6k Kick)
Snare Drum
–
Right balance of: stick, head, shell parts, snares
• Common approach – dynamic mic, 1/2 “ inside rim, 1” above head
• Use polar pattern “angles” to keep bleed out from hihat
• Keep out of way of drummer
–
–
–
–
AE3000 series condenser can handle transients and SPL as
alternative to dynamic mic
ATM650 for classic “57” sound
ATM350 miniature condenser (clip-on)
Second mic on bottom (pick up snares), out of phase
with top mic.
650_drums_2
Microphones: AE3000 – Best (if condenser sound is desired )
ATM650 – Better (Best for classic “57” sound)
Pro63 - Good (MB 6k Snare/Tom)
High Hat
–
–
Right balance of: sharp attack and high frequency
Small diaphragm condenser
ATM450_drum...
• 4-6” above outside edge furthest from snare, face mic straight down –
balanced tone
• Closer to top cymbal – more bell like sound
• Horizontally outside edge of top cymbal – watch for rush of air when
hat closes
–
Use polar patterns and “angles” to minimize bleed from snare
Microphones: ATM450 – Best (Side address for ease in positioning)
AE5100, AT4041, AT3031 – Better
Pro37R - Good (MB 4k)
Toms
–
Primarily looking for tone
• Common approach – dynamic mic, 1/2 “ inside rim, close to top head
• Closer mic is to head, more proximity effect (low freq)
• Use one mic to pick up two neighboring rack toms, several inches
above top head, half way between rims.
• Watch for interaction between mics
–
–
–
AE3000 series condenser can handle transients and SPL as
alternative to dynamic mic
ATM35 miniature condenser (clip-on)
AE2500 or ATM25 for floor toms
• Alternate mic them from bottom up inside shell if there is no bottom
head.
Microphones: AE3000 – Best (if condenser sound is desired )
ATM250 – Better (ATM350 clip-on)
Pro35ax - Good (MB 6k Snare/Tom)
Floor Toms: AE2500 – Best (requires 2 input channels)
ATM250 – Better
Pro25 – Good (MB 6k Kick)
650_dru...
Overhead (Cymbals)
–
–
Overall balance of all cymbals
Small diaphragm condensers
• 15-18” above cymbols
• Watch 3-1 spacing rule
• Alternate is stereo pair in X-Y configuration
–
These mics will pick up bleed from other drums
Microphones: AT4050 – Classic for major tours…
AE5100, ATM450 – Best
AT4041, AT3031 – Better
Pro37R - Good (MB 4k)
Other Percussion (Latin congas, etc)
–
Primarily looking for tone
• Condenser mic 1-3 feet from instrument
• When using multiple mics watch 3-1 spacing rule
• ATM35 Clip-on mics on individual instruments.
Microphones: AE5100 – Best (AT4053 – narrower pattern)
ATM450 – Better (ATM350 clip-on)
Pro35ax - Good (MB 4k)
Down & Dirty – Good Drum Sound
–
4 Mic setup
• Kick
• Snare
• Overhead
Best
Better
Good
AE2500
AE3000
AE5100(2)
ATM250
ATM650
ATM4501(2)
Pro25
Pro63
Pro37(2)
The overhead mics will pick up cymbals and toms,
snare mic can pick up hi-hat. Easy to balance, fewer
mixer channels
Application – Mics on Other Stuff
• Orchestral Instruments _ Bell Choir
–
–
–
–
Locate 1-2’ above players
Spaced pair.
Remember 3-1 rule.
AE5100, AT4051 – Best
Pro 37 – Good
• Orchestral Instruments _ Strings
–
–
–
–
Locate 1-2’ above players
1 mic per two players
Use UniMix combiners to gain more
mixer input channels.
AE5100, AT4051 – Best
ATM450, AT4041 – Better
AT3031, Pro 37 – Good
• Orchestral Instruments _ Violin (mounted)
– Use Velcro mic mount for maximum
isolation or on performer
that moves around.
– Mount on strings below bridge.
– Gives a bright sound
ATM350 – Best
• Orchestral Instruments – Cello, Bass
– Upright bass and cello have two “f” holes,
one on either side of strings.
– Mic can be clipped to “f” hole
– Place mic 6” from “f” hole for good balance
of instruments key tones
– Closer to “f” hole, more low frequency
– Place mic closer to bridge for extra treble
ATM350 – Best (Clip-on)
AE5100, ATM650 – Better
Pro 35ax – Good
• Orchestral Instruments _ Flute
– Sound comes out of mouthpiece (breath) and
tone holes
– Locate mic between mouthpiece and middle
keys, 8-12” away form instrument.
– Further away results in more balanced tone
AE5100, AT4051 – Best
Pro 37 – Good
Application – Mics on Other Stuff
• Woodwinds - Saxophone
– Sound is distributed between
finger holes and horn’s bell
– Mic aimed into bell – bright sound
– Mic clipped to bell will give punchier
sound and can be wireless
ATM350 – Best (Clip-on)
AE3000, ATM610 – Better
Pro 35ax – Good
• Woodwinds - Clarinet
– Sound is distributed along length of
instrument (bell & finger holes)
– Three distinct tones – bell, middle third,
top third of instrument
– Mic perpendicular, aimed away from bell
for more even tone and less high freq.
• Orchestral Instruments _ Brass
– Large diaphragm condenser handheld
type mics 1 - 2’ from horn bell.
– For tubas, sousaphones and baritone
horns, mic at 3’ from bell
– Two or three players can share a mic
– Use clip-on mic for maximum isolation
and brighter sound
AE5100, AT4051 – Best
ATM450 – Better
Pro37 - Good
AE5400, AE3300 – Best
AE6100, ATM610 - Better
ATM350 Clip-on – Better
Pro 63 – Good
• Orchestral Instruments – French Horn
– French horn bell faces rear of player
– Place mic behind player aimed toward bell
for natural sound
– Reflective surface behind player helps
even out sound
AE5400, AE3300 – Best
ATM250 – Better
Pro 63 - Good
• Room Ambiance for Ear Monitors
– Provides performers with room sound in
isolated ear monitors
– Use shotgun mics to minimize front of
house PA sound from in the ears
– Can also be used for recording/video
AT4071, AT4073 – Best
AT897 – Better
Microphone Terminology
•
•
•
•
•
•
•
•
•
•
•
•
•
Adapter Mount: Term used to describe gooseneck microphones with a 5/8"-27 threaded rotating
collar which screws into the 5/8"-27 threads of a mic stand, mounting stud, etc.
Attenuate: To reduce the amount of energy contained in an electrical or radio frequency signal.
Also, to reduce the intensity or level of sound waves.
Balanced Circuit: A signal-carrying circuit with two active electrical conductors of equal
impedance on which equal, but oppositely-phased signal components may exist. Usually both
conductors are enclosed within an overall metallic shield, which does not carry the signal. Widely
used to reduce the pickup of hum and noise in audio system cabling. Also referred to as a
balanced line.
Bi-directional: Operating primarily in two directions, 180 degrees apart. See Figure-8.
Boundary Microphone: A type of microphone that detects sound pressure level changes at a
boundary of the acoustic space in order to reduce interference between direct and reflected
sound.
Capsule: The portion of a microphone that converts acoustic energy to electrical energy. Often
includes shock mounts, acoustic isolators, protective covers and electronic circuitry in addition to
the basic transducer. Also called an element.
Cardioid: Describes the pickup pattern of one type of directional microphone, which is roughly in
the shape of a heart. Such microphones are several dB less sensitive to sound arriving from
sources at angles 90 degrees or greater away from its front.
Clipping: In audio equipment, severe distortion caused by a signal whose peak level exceeds the
capabilities of the device processing the signal. Results in the flattening of the signal peaks as if
they had been "clipped" off.
Condenser Microphone: A type of microphone in which the diaphragm is one plate of a capacitor
(condenser) containing an electrical charge. An electrical output signal is generated by detecting
the variations in the charge present in the capacitor resulting from movement of the diaphragm by
sound waves. Some are called capacitor microphones.
Diaphragm: The portion of a microphone which is mechanically moved by incident sound, thereby
allowing conversion of sound energy to electrical energy.
Directivity: The property of transmitting or receiving energy more strongly in some directions than
in others.
Dynamic Microphone: A type of microphone consisting of a diaphragm mechanically attached to
a coil operating in a magnetic field. Sound pressure variations cause movement of the coil within
the magnetic field, producing a small voltage across the coil terminals.
Dynamic Range: The range in dB between the noise floor of a device and its defined maximum
output level. The term applies to both audio devices and RF equipment, but the maximum output
level is defined differently.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Electret Condenser Microphone A type of condenser microphone whose transducer contains
an electret material that permanently retains an electrical charge, and does not require the
external voltage source required by other types
of condenser transducers to polarize the diaphragm.
Feedback In acoustics, the undesirable leakage of audio from loudspeakers back into a
microphone, resulting in a loud squeal or howling sound, or in less severe cases, a hollow ringing
sound quality or whistles.
FET Field-effect transistor, typically used as an impedance converter at the element in a
condenser microphone.
Figure-8 or Figure-of-8 A bi-directional microphone pattern, with two equal lobes 180 degrees
apart. Also describes some antenna patterns, such as that of a dipole.
Gain Before Feedback The amount of total gain that can be achieved in an audio system, from
microphone to speakers, before the onset of acoustic feedback.
Ground Lift Switch or Ground Lifter A switch to disconnect the shield of a balanced audio
cable from the
local equipment ground. In certain situations, can eliminate ground loop and hum problems.
Ground Loop A condition where the local grounds at each end of a length of cable are at a
different AC potential.
This sometimes causes hum and noise problems and may require the use of corrective
measures such as a ground lift switch on the equipment.
Harmonic Distortion: Undesired signal harmonics at the output of a device which were not
present at the input.
Hi-Z: (High impedance) A loosely-defined audio term used to describe devices whose input or
output impedance is greater than approximately 5,000 ohms. High-impedance mics typically are
20,000+ ohms.
Hum: A continuous undesired audio component at the frequency of the incoming AC power line,
or a harmonic.
Hypercardioid: Describes the pickup pattern of one type of directional microphone. Its front lobe
is somewhat narrower than that of the cardioid microphone, and it possesses a small rear lobe in
which the sound pickup is out-of-phase with that of the front lobe.
Hz: An abbreviation for Hertz, the number of cycles per second of a signal.
Impedance: The opposition to the flow of an AC signal offered by a circuit or device.
kHz: Kilohertz, 1,000 Hertz, or one thousand cycles per second.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Lavalier Microphone A type of miniature microphone that is usually worn fastened to clothing
somewhere near the user's mouth. Also referred to as a clip-on or lapel microphone.
Line Level: Audio signals whose maximum average levels can exceed approximately 0.5 volts,
or a circuit which can output or accept such signals.
Lo-Z: (Low impedance) A loosely-defined audio term used to describe devices whose input
or output impedance is less that approximately 5,000 ohms. In microphones, Lo-Z commonly is
50 - 1,000 ohms.
MHz: Megahertz, one million Hertz, or one million cycles per second.
Mic Level: Audio signals whose level is similar to those of microphones, that is, generally
ranging from roughly 0.001 volts (1 mV) to 5 volts.
Mini-plug: A miniature phone plug, available in both "mono" and "stereo" versions. The most
common size for audio use is 3.5 mm.
M/S Stereo Microphone: Mid-side or mono-stereo microphone. A type of stereo microphone
with both a cardioid transducer facing forward and a "figure-8" transducer which is mounted
such that its maximum sensitivies are pointed "sideways." An electronic circuit is required to
develop the two stereo channels from the two transducer outputs. With this technique, it is
possible to combine the transducer outputs in such a manner as to vary the stereo image.
Multi-pattern Microphone: A type of microphone with a switch to allow selection between
more than one polar pattern.
Mute: To turn off or silence an audio signal.
Neodymium: A rare metallic element that can be made into particularly strong magnets.
Superior to the magnetic materials more commonly used in dynamic microphones.
Omnidirectional: Describes a device such as a microphone or antenna that operates equally
well in all directions.
Overload: A condition where the signal levels present exceed the capabilities of a device,
causing an undesirable consequence.
Pad: An attenuator, typically used to reduce mic output to avoid equipment input overload.
Passive: Lacking any active devices or active circuitry.
Phantom Power: A specific configuration for remotely powering a microphone containing
active circuitry, especially a condenser microphone, by means of its audio cable. DC voltage is
superimposed upon both conductors of a balanced line with respect to ground such that
dynamic and other "non-phantom" microphones are not adversely affected. It should not be
confused with other methods, especially those often used with wireless transmitters, that do not
utilize a balanced line. These other techniques are usually referred to simply as "bias voltage."
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Phase: ("In-phase/Out-of-phase") Actually refers to the polarity of an electrical or acoustic signal.
If two or more signals or devices are "out-of-phase" with respect to each other, cancellation or
other disturbance of the combined output can result. Some examples of operating phase
(polarity) definitions: "Positive sound pressure causes positive output" (microphones) or "positive
input causes positive acoustic output" (speakers).
Phase Cancellation (Interference): Undesirable dips and peaks in frequency response caused
by mixing the outputs of two microphones which are picking up the same sound but with different
arrival times. For example, this can occur when two microphones are placed near each other, but
still with space between them; or when wireless microphone users stand next to each other. Also
referred to as acoustic phase interference. See also "3:1 Rule".
Phone Plug Connector: A type of plug-in audio connector with a 1/4-inch (6.3 mm) diameter
metal contact sleeve, and either one or two signal contacts. Widely used in the telephone
industry, particularly in the past, hence the name.
Polarized: In condenser microphones, the source of the charge contained in the microphone
capsule. Transducers may be of the internally polarized (electret) type, or may require an outside
source of polarizing voltage (externally-polarized).
Polar Pattern: A plot of a device's sensitivity or efficiency as a function of the angle around the
device. Widely used to characterize the performance of microphones and loudspeakers.
Pop: An undesirable short duration microphone output, often caused by explosive exhalation of
air during the formation of certain vocal sounds.
Pop Filter: A material, usually some form of acoustically-transparent foam and/or mesh, used on
or in microphones to reduce the effects of breath blasts and air currents.
Preamplifier: A type of amplifier specifically designed to amplify low-level signals.
Proximity Effect: The exaggeration of low-frequency sounds in a directional microphone when it
is very near the sound source.
Quick Mount: Term used to describe gooseneck microphones with an integral output connector
which plugs into a matching jack.
RFI: Abbreviation for Radio Frequency Interference.
Sensitivity: In wired microphones, phono cartridges, etc., the amount of output for a given input.
Shock Mount: In microphones, a mechanical device, usually incorporating some type of shockabsorbing elastic material, designed to acoustically isolate the transducer from shock, vibration
and handling noise.
Both internal and external shock mounts are commonly used.
Shotgun Microphone: A type of highly-directive microphone having a very narrow elliptical
pattern and extremely reduced pickup from the sides and rear.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Signal-to-noise Ratio or SNR: The ratio, normally expressed in dB, between the level of the
desired signal and the level of unwanted noise.
Sound Pressure: Fluctuations in air pressure due to the presence of a sound.
This sound pressure is expressed in units such as Pascals, microbars, or dynes/cm2.
Sound Pressure Level or SPL: A standard measurement of the amplitude of sound,
expressed as the ratio in decibels between the measured sound pressure and standard
reference of 0 dB SPL = 20 microPascals = 0.0002 dynes/cm2.
Subcardioid: Describes the pickup pattern of one type of directional microphone, which is only
modestly directional but retains some degree of rejection of sounds arriving from the sides and
rear. Provides a somewhat broader and less well-defined pattern than does a standard cardioid
microphone.
Suspension: The mounting for a microphone capsule, generally designed to provide some
degree of mechanical isolation between the capsule or transducer and the microphone body in
order to reduce handling noise.
T.H.D.: Abbreviation for Total Harmonic Distortion. The sum total of all undesired harmonic
energy present in an output signal, usually expressed as a percentage of the total output signal.
"3:1 Rule“: ("3-to-1 Rule") Rule-of-thumb ratio for the minimum distance mics should be
spaced apart ("3 times X"), compared to their distance from the sound source ("X").
Transducer: In audio, a device to convert sound to electrical energy or vice versa.
Microphones and loudspeakers are two type of transducers. Also refers to the portion of a
microphone that is directly involved with conversion of sound energy to electrical energy.
Transformerless: An electronic circuit capable of outputting or receiving a balanced audio
signal without the use of a magnetic transformer. Transformerless circuits generally have wider
frequency response and lower distortion than circuits using transformers.
Unbalanced: Refers to a signal-carrying circuit with one electrical conductor and an overall
metallic shield. Also referred to as an unbalanced line.
Unidirectional: Describes a device which radiates or receives energy more efficiently from
a single direction than from all other directions.
X/Y Stereo Microphone: A type of stereo microphone where two directional transducers are
mounted such that their patterns are pointed outward at angles of approximately plus and
minus 45-to-60 degrees from the front of the microphone.
XLR Connector: Designation for a type of connector commonly used in professional audio. For
balanced audio cables, particularly for microphones, the 3-pin versions, male and female, are
most often used.
Z: Symbol for impedance.
Sound Quality Terms Glossary
•
•
•
•
•
Airy: Spacious. Instruments sound like they are surrounded by large reflective space. Some leakage
between mics, some reverb (pleasant amount), extended high frequency response (15 – 20 kHz).
Bassy: Emphasized low frequencies (below 200Hz).
Boomy: too much bass or low frequency sound around 125 Hz.
(Often due to poorly damped low frequencies or low frequency resonances.).
Boxy: Sounds if music is enclosed in a box. (Sometimes and emphasis in 250 – 500 Hz range.)
•
Breathy: Audible breath sounds on vocals, flute, sax or other wind instruments.
Good or emphasized high frequency response.
Bright: Strong in treble range or high frequency emphasis.
•
•
•
Brittle: Slightly distorted or harsh high frequencies.
Clean: Sounds that are free of noise, distortion or leakage.
Colored: Sounds that have timbres not true to life. Non-flat response, peaks or dips in response.
•
Crisp: Extended high-frequency response often referring to cymbals.
(Think of bacon frying or crispy chips.)
Dark: Opposite of bright (often dull sound with weak high frequencies).
•
•
•
•
•
•
•
•
•
Detailed: Articulate, easy to hear tiny details in music. Good high frequency response.
Dry: Sound without any effects or processing.
Edgy: Too much high frequency, almost distorted highs or having unwanted harmonics, raspiness.
Fat: Full and warm sound, good low frequency response (100-300 Hz), strong fundamentals
related to harmonics.
Gentle: Opposite of edgy, Upper harmonics (highs and mids) weak or not exaggerated.
Grungy: Lots of harmonic distortion, sounds dirty.
Harsh or Hard: Too much upper midrange (around 3 kHz) or peaks in upper midrange (2 – 6 kHz).
Hollow: Too much reverberation or a mid frequency dip (500 – 700 Hz).
•
•
•
Mellow: Reduced high frequencies, not edgy, but not hollow.
Muddy: Not clear. Weak harmonics, IM distortion, too much reverb or leakage at low frequencies.
Nasal: Vocalist sound like they are singing with their nose closed. (Think of a head cold.)
•
•
Piercing: Strident, hard on the ears. Sounds having sharp narrow peaks in response (3 kHz – 10 kHz).
Presence: Emphasized response (5 kHz). Sounds have some edge, punch, detail closeness and
clarity. Vocals stand out in front of other sounds in mix.
Punchy: Good dynamics reproduction, good transient response. Sometimes a bump around 200 Hz.
•
Sound Quality Terms Glossary
•
Presence: Emphasized response (5 kHz). Sounds have some edge, punch, detail closeness and
clarity. Vocals stand out in front of other sounds in mix.
•
•
•
Raspy: Harsh sounds, peaks in 6 kHz region, makes vocals sound to sibilant or piercing.
Round: High frequency roll-off or dip, not edgy. Sometimes equated with full.
Sibilant: Exaggerated “s” and “sh” sounds in vocals. Rise in response around 5 – 10 kHz.
•
•
•
Sizzly: Too much highs on cymbals. Sounds like water on hot metal.
Smeared: Lacks detail, as if sounds were jumbled up. Poorly focused images.
Smooth: Easy on the ears and not harsh. Flat frequency response (especially in midrange).
Lack of peaks and dips in response.
•
•
•
Squashed: Too much compression.
Thin: Fundamentals are weak relative to harmonics.
Tight: Good low frequency transient response and detail.
Absence of ringing or resonance (kick drum).
Tinny: Narrow frequency response (sounds like a telephone), weak lows, peaky midrange.
Transparent: Easy to hear into music, detailed and clear, not muddy.
Wide flat frequency response, very low distortion and noise..
Tubby: Excessive low frequency resonances. Sounds like singing in a bathtub.
Excessive mid bass (250 Hz).
•
•
•
•
Warm: Good bass, adequate low frequencies. Not thin, adequate fundamentals relative to
harmonics.
Remember… It’s all about the listening!
Where to Find Out More…
Interactive web site
WWW.audio-technica.com
– Guide to A-T products
– Microphone fundamentals
– Wireless microphone applications
– Frequency selection tools

Microphones - Pro Audio Systems

Transcription

Similar documents

PR 20-22out - Heil Sound

Superlux Condenser Microphones

M606 Characteristics

Multi-Sync BTH-300 to Radio and/or Mobile

Professional Audio Analyzer PAA3X

Spec Sheet - Performance Audio

Sony C-37A microphone manual

SCX25A - Audix

soundelux e47 - RecordingHacks

A History of Audio-Technica Microphones