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WHAT ARE THE 3 PRIMARY FACTORS DETERMINING POWER LOSS IN
SPEAKER CABLE RUNS?
- cable length
- cable gauge
NAME 3 ELEMENTS THAT HAVE THE GREATEST EFFECT ON SYSTEM DESIGN?
NAME 3 TYPES OF SPEECH INELIGIBILITY MEASUREMENTS?
- SPEECH TRANSMISSION INDEX
- CLARITY RATIO
WHAT IS THE NAME USED TO DECRIBE UNITS OF ABSORBTION?
DEFINE CRITICAL DISTANCE.
the distance from the source where the reverberant and direct sound fileds are equal in level
HOW DOES A TEMPERATURE LAPSE AFFECT SOUND?
during the day the air temp is warm close to ground. this temp decreases as you increase height. the sound bends toward the sky
HOW DOES A TEMPERATURE INVERSION AFFECT SOUND?
during night air temp is lower close to ground and increases with height. the sound bends toward the ground
WHAT IS PURPOSE OF “A WEIGHTING” ON AN SPL METER?
this contour is designed to approximate the ear at the 40 phon level. this weighting is used to measure ambient sound levels
WHAT IS PURPOSE OF “C WEIGHTING” ON AN SPL METER?
- this contour approximates the ears response at very high sound levels.
- often used to measure traffic noise
WHAT IS THE RECOMMENDED SPL METER WEIGHTING? WHY?
- A weighted slow.
- it focuses attention on the frequencies that sound the loudest and are vital for communication.
NAME SOME COMMONLY USED SPEAKER CABLE CONNECTORS USED BY
PROFESSIONAL SOUND COMPANIES (MANUFACTURER AND MODEL).
USING A STANDARD WIRE TABLE WE DETERMINE THAT FOR EACH
300METERS/1000FT OF 10 GAUGE WIRE, WE HAVE 1Ω OF RESISTANCE. HOW
MUCH RESISTANCE WOULD AN 80METER RUN OF SPEAKER CABLE HAVE?
____________ * UNIT Ω = TOTAL Ω
- _______ * 1Ω = 0.53Ω
WHAT DOES THE 5% RULE STATE?
cable resistance should never exceed 5% of load resistance
WHAT IS “DAMPING FACTOR”?
a numerical indication of how well an amp can "control" a loudspeakers cone motion
WHAT WOULD BE THE ELECTRICAL DAMPING FACTOR OF A LOUDSPEAKER
WITH A DC VOICE COIL RESISTANCE OF 8Ω, AN AMPLIFIER OUTPUT
IMPEDANCE OF .001Ω, AND A TOTAL CABLE RESISTANCE OF .53Ω?
R (VOICE COIL)
Z (AMP OUT) + R (CABLE)
- .001Ω + .53Ω
LIVE AUDIO SYSTEMS ARE OPTIMIZED FOR _____________ ________________.
PROGRAM SOURCES VARY IN ______________, _________________ AND ________________.
NAME THE 3 TYPES OF PROGRAM SOURCES.
WHAT IS A MIXER’S MAIN JOB WITH REGARD TO PROGRAM SOURCES?
scales mic level to line level
WHAT ARE 3 MAIN TYPES OF SIGNAL PROCESSING?
POST MIXER PROCESSING IS MAINLY _____________________ IN NATURE.
technical (as opposed to artistic)
WHERE DO WE USE “MATCHED” OR “TERMINATED” INTERFACE?
- wireless antenna systems
- video systems
- long transmission lines
IN A ___________ AUDIO CIRCUIT, IT IS BENEFICIAL TO HAVE THE LOAD IMPEDANCE ____ TIMES THE SOURCE IMPEDANCE TO INSURE EFFICIENT ________TRANSFER FROM DEVICE TO DEVICE.
WHY CAN’T WE “Y” 2 OUTPUTS TO AN INPUT?
- outputs will both try to drive each other causing low impedance causing high current to develop
- outputs are low impedance and meant to drive the higher impedance of the input
LOUDNESS AND POWER RELATE TO THE ________ OF THE SIGNAL.
CLIPPING CAUSES ____________ _________________. WHICH CAUSES THE SIGNAL TO SOUND
WHY IS MONITORING THE PEAKS OF SIGNAL IMPORTANT?
monitoring peaks can help us avoid distortion
WHY IS MONITORING THE RMS OF SIGNAL IMPORTANT?
monitoring RMS can help us aviod loudspeaker damage
WHAT IS THE DIFFERENCE BETWEEN A “QUASI‐PPM AND A TPPM?
- A quasi-PPM has a 5-10ms integration timeA quasi-PPM will often read 8-10 dB lower than a TPPM
- A true PPM (TPPM) has instant ballistics that read out any short term peaks.
WHAT IS THE MAIN DRAWBACK OF USING A PPM?
- a PPM cannot monitor loudness or RMS
- Loudness & RMS affect hearing saftey and Potential loudspeaker damage
0 DBFS CAN BE REFERENCED TO A __________ OR A ___________ WAVE.
WHEN WOULD A TRUE PEAK PROGRAM METER BE USEFUL?
when recording to avoid short term peaks that would cause
WHAT IS THE RESPONSE OR INTEGRATION TIME OF A VU METER?
HOW MANY VOLTS DOES 0VU EQUAL?
WHAT IS CREST FACTOR?
The difference between peak and average signal Crest factor in dB=10log(peak/average)
WHAT IS THE CREST FACTOR OF A SINE WAVE?
WHAT IS THE DIFFERENCE BETWEEN AES PINK NOISE AND TRADITIONAL PINK NOISE?
AES pink is filtered so that it has 6dBCF and traditional pink noise has a crest factor of 10dB
WHAT IS THE CREST FACTOR OF TYPICAL MUSIC?
what is dynamic range
peak level - noise floor
what is thermal noise
- the result of atoms bumping into each other
- electronic noise
WHY ARE WE FORCED TO DEAL WITH SYSTEM GAIN STRUCTURE?
- there is no standard noise floor level
- there is no standard peak input / output level
HOW MANY VOLTS DOES 0 dBU EQUAL?
- .775 v
- dervived from old telephone specs based on 600Ω & .001 watt (0dbm)
WHAT DEVICES ARE USED TO ADJUST ATTENUATION WHEN SETTING A SYSTEM’S GAIN STRUCTURE?
- external pads
- onboard input / output controls provided they are "BEFORE" the pre-amp
WHAT IS THE PURPOSE OF A SYSTEM LIMITER?
to act as an early waring device that allows YOU to take measures to protect the system.
WHAT RATIO SETTING IS BEST FOR A SYSTEM LIMITER?
8:1 or greater
WHAT 3 METHODS ARE USED TO DETERMINE CLIP POINTS IN A SYSTEM?
- piezo magic
- onboard indicators
BEFORE PHYSICALLY SETTING GAIN STRUCTURE, WHY DO YOU FIRST RUN SIGNAL THROUGH THE SYSTEM?
- to check the integrity of the system
- you must fix grounding / power / driver issues before attempting to cal a systems gain structure
WHY WOULD WE ZERO OUT AN EQ BEFORE ATTEMPTING TO SET GAIN STRUCTURE?
- any cuts or boosts will affect the EQ output during cal
- log existing curve before zeroing to prevent possible hurt feelings
CALCULATE THE VOLTAGE SEEN AT AN OUTPUT WITH A METER READING OF 12dBu.
10___ * ref = volts
WHAT IS AMPLIFIER INPUT SENSITIVITY?
the amount of voltage req at an amps input to produce full rated output
What are the two components that make up a radio wave?
- Magnetic ("H" feild)
- and electrical ("E" fields)
What is a carrier wave?
Base unmodulated frequency the TX and RX remain locked to
Name 2 types of modulation
What type of modulation is used for wireless microphone and in-ear monitor systems? Why?
Frequency modulation has a wider frequency response (50-16k) and better dynamic range. (90+ db)
What 2 types of audio signal processing are used in transmitting and receiving? why?
- Pre/post emphasis EQ
What does true diversity mean?
The ability to sample the radio field from 2 or more locations and/or the ability to select/combine the resulting signal.
What diversity design is most common?
Receiver switching diversity
What is the minimum size for a transmitting or receiving antenna?
1/4 the size of the wavelength you are transmitting or receiving
What is the best way to maintain maximum efficiency between a transmitting and receiving antenna?
Line of sight between TX and RX
(T) Name 4 types of commonly used antenna designs
- Ground plane
- logarithmic periodic dipole array (LPDA)
- circularly polarized
(T) What are the 2 types of antenna distribution and when would we use them?
- Passive (up to 2)
- Active (more than 2)
What causes "drop out", "noise up" and "hits"?
- Dead or dying batteries (alkaline)
- Multi-path effects
What is the purpose of the Squelch Circuit?
To mute the audio output of the receiver when RF signal level falls below a set threshold.
Which frequency band has its transmitter power limiter to 50mW?
- VHF (Very High Frequency)
- 30 to 300mhz
Which frequency band has its transmitter power limiter to 250mW?
- UHF (Ultra High Frequency)
- 300 to 3Ghz
Which frequency band is illegal to use as of June 2010?
UHF 700 to 805 MHZ
Two channels have been allocated in every major city market for wireless use. Where are they located?
UHF-TV Channel 37
Name some unique benefits ear monitor systems provide
- Safer on ears
- Less stage volume
- Less chance for feedback
- Better sounding mix
- Quick setup and teardown
- Less bulk on truck
Give some application examples for an in ear monitor system.
- Live performance
- Studio monitoring
A basic wireless in ear monitor system consist of:
- Multiband peak limiter/processor
- Ear molds
Why is it important to drive an in ear monitor system transmitter properly?
- If the input is too low, you will have to operate the receiver volume at too high a level leading to excessive noise.
- If the input is too high, you will cause overmodulation distortion. There
- is also a danger of bleed into adjacent radio channels.
Why is a peak limiter necessary at the transmitter input?
- To prevent hearing damage due to level spike or feedback loop.
- To enhance the mix.
What band positions typically use a hardwired in ear mix as opposed to a wireless one?
What is the first thing you need to do to obtain custom ear molds?
Go to a hearing aid center or an audiologist and have impressions taken of your ears.
How does an ambient microphone fed into a musician's in ear monitor mix help the musician?
- it helps the musicians hear crowd response
- Helps with localization when using isolating molds
- Allows communication on stage
Explain why a monitor wedge would be used in combination with an in-ear mix.
Low end supplement
What is multi-band limiting?
Multi-band limiters allow separate limiter control over multiple frequency bands.
Name some techniques used to enhance the low end of an in ear mix.
- Bass "shaker"
- Side fill subs
what is "balanced"
equal impedance (Z) compared to ground