sound reinforcement midterm
How may Pre-fader sends and how many post-fader sends is the Midas Venice capable of?
- 2 pre FX sends- 2 post mon - 2 pre/post aux 4 pre 4 post
How many channels of audio does an NL8 carry?
- 4 Channel/8 Conductor
What radio frequency spectrum was recently auctioned off by the FCC?
- 600 MHz band - all wireless operating in 700 MHz frequency range will be illegal in 2020
What are the three controls on a parametric EQ?
- Adjustable Q- Adjustable Frequency- Adjustable Gain
What are two advantages of using an active DI box over a passive DI box?
- An active DI box includes a preamplifier to provide a stronger signal and higher input impedance- Active DIs can be designed to be extremely quiet, hi-fi, and transparent tonally Can handle lower output devices, Clearer signal. An active DI can handle lower-level signals and still sound good, and also can be designed to be more transparent than a passive DI.
What are the three stages of reverberation?
- Direct- Early reflections ( <80ms)- Late [present] reflections (>100ms) Direct Sound, Early Reflections, Decay
What is the likely result of a person cupping a microphone like in the image below?
The Microphone will be much more likely feedback.
Define Diffraction of a sound
The change in direction of travel of the sound waves caused by the interaction with an object, where the waves bend around the object The bending of waves around the corners of an obstacle.
Which of the following attributes of a Permanently installed PA system are false?
The system can easily be expanded.
Define RT60.
- The amount of time it takes the reverberation of a room to decay 60dB below the initial SPL of the direct sound- RT: Reverb Time The time it takes sound to decay to -60dB
Phantom Power is 48 volts of power supplied through the microphone cable on pins...
2 & 3
When phantom power is turned on at the mixer, +48v is supplied to pin(s) ___ of the XLR plug of a microphone.
2 and 3
How many conductors does an NL 2 have in it?
2 conductors
What distance should you keep your unbalanced signal cables under?
20 feet or less
What it the maximum compression ratio recommended by Poff when using a compressor on your main Left/Right in your drive rack?
2:1
If I have a stage monitor directly in front of my musician, what mic pattern is the best choice for me to use?
cardioid
Describe what happens when a musician covers over the porting of a microphone.
causes boost in high-mid frequencies/ feedback/ worse directionality The mic becomes omni-directional
What type of transducer is in the Shure KSM9?
condenser
What is the term given for the amount of dynamic range between the RMS and peak values of a sound signal in my system?
crest factor - difference b/n peak and RMS level of signal (in dB)
the change of direction of travel of sound waves caused by the interaction with an object.
diffraction
when the energy of a sound is propagated in many directions by an irregularly shaped object.
diffusion
What are the most common types of microphones in live sound reinforcement? (Choose all that apply)
dynamic and condenser
A Post-fader aux send is used for:
effect sends They send a signal out from a particular channel to an effects processor, and then it re-enters through an aux return.
What will happen when a wireless microphone's antenna makes contact with skin?
energy is reduced and may cause audible noises known as dropouts
Digital processing is a serial process of several discrete steps where each step takes a small amount of time to complete. This amount of time is known as _____.
latency
What will happen to your audio if you use a line level cable in leu of a speaker cable between your amp and your speaker?
lose all low end The cable will melt. a lot of things can go wrong
What happens to your audio signal when you go from a balanced to unbalanced connection?
lose half the signal The signal will be unbalanced
The sensitivity of a microphone directly relates to its...
mass of the diaphragm.
The sensitivity rating of a microphone is related to the...
mass of the diaphragm.
The location from which the speakers located on the stage for the musicians is mixed.
monitor world
Define Squelch.
mutes receiver when no signal is present Mutes when no signal is present (Gate)
What shape does an omni antenna resemble in a wireless microphone system?
trapezoid
A linear phase filter preserves the time relationship of a complex waveform and, therefore, eliminates the distortion of transients in dynamic music.
true
A room that has too much absorption will sound dead, and a room with too little absorption can make it difficult to hear.
true
I have read and understand the policies listed in the syllabus for this class.
true
Phase is not only a description of where two waveforms are in their cycles but also where they are in time with each other.
true
The frequency range of a microphone describes the highest and lowest frequencies a microphone responds to while a frequency response graph show how sensitive the mic is at different frequencies.
true
The inverse square law states: "For every doubling of distance from a sound source, the intensity of a sound is reduced by four times it's strength."
true
When choosing a microphone for any application, you should consider the SPL of the source, distance from the source, coverage area and need for isolation, feedback control, tone, and cost.
true
the equipment in room 201 is not available for students to use and/or borrow for personal projects, recording sessions, and gig's outside of the class.
true
What is natural sound?
unprocessed straight from source
I have used condenser microphones at an outdoor event when I discover that dew has formed on them in the middle of the night. What should I be concerned about?
unwanted noise (hissing, popping, crackling)- change the actual sound of the microphone (frequency response shifts, changes in transient response)complete failure The frequency response of the mic
If I am using a 4th order filter in my drive rack, how many dB per Octave is my filter reducing the signal by?
12 6 x 4 = 24 dB/octave
Name 2 kinds of equipment typically hooked up through a DI box.
- Electronic keyboards- Drum machines- Guitar amps Bass Acoustic guitar
What are the 3 rules to sound?
- Make sound- Continue making sound- Make good sound (Louder is not better → better is better)
3 pin XLR Connector
- Male/Female connectors- audio travels in direction of pins- Balanced connection- Used for microphones at mic level (-60 to -40dBu), as well as line level signals (+4dBu)- audio cable 45 ohms- also used for AES/EBU (AES3) digital connections with a fixed 110ohm cabling
Name 3 reasons for making a system diagram?
- Signal flow - Know where everything is going - Troubleshooting
Which gauge would be the thicker wire, 12 gauge or 16 gauge?
12 gauge- lower number = thicker cable
Name the three types of cable shielding.
- foil - spiral wrapped - braided wrapped
Name 3 things you would see on a stage plot.
- instruments- monitors- amps/ DIs Mic placement, Instrument Placement, Monitors
List 3 of the 5 things you can to do Avoid Drop-outs and interference on a wireless microphone.
- mount antennas high (8-10 ft) and minimum 1/2 wavelength apart- line of sight- transmitter/ receiver apart 10+ ft- place antennas off axis and not touching- turn off cell phones avoid obstacles in the path of the mic
What is diversity and why do we use it as it pertains to wireless microphones?
- utilizes multiple receiver channels/antennae- prevents dropouts Better to use 2 antennae so they can switch between them.Prevents dropouts utilizes multiple receiver channels/antenna, used to prevent dropouts
Typical Consumer signal levels are at:
-10 dBV
Typical line level for an audio device is this level
-10 dBV for consumer audio, +4 dBu for pro audio
What is the pin out of a TRS connector?
-tip, ring, sleeve -balanced connector sleeve = shield tip = hot (+) ring = cold (-)
What are three items listed for each channel on an input list?
1. Microphone 2. Phantom power3. Instrument
What are the different types of distortion in a sound system?
1. Overdriven sound 2. Harmonic Distortions 3.Intermodulation
Give 3 of the Primary functions of a mixer:
1. Setting gain structure2. Combine signal 3. Processing signal (internal/external)4. Route signal Set gain structure, Combine Signal, Process Signal
When using an 31 band graphic EQ, the frequency band filters adjust ____.
1/3 of an octave only when placed at maximum boost.
TRS cable
1/4" TRS -tip, ring, sleeve -balanced connector - +4dBU patch, interconnection between devices, headphone jack, send/return cable connections
Name the 3 most common types of graphic EQ's.
10, 15, 31 Band. ??
How many outputs would I have in a 4 way stereo crossover network?
8
What is Phantom Power and what is it used for?
48V generated from console or a power source to power condenser mics Phantom power is +12-48V that is sent to condenser microphones and active DI boxes
How long do I need to set the delay on my speaker if it is 5 feet away from the sub?
5/1130 = 4.42 ms 4.4ms
In general, a low impedance microphone is less than...
600 Ω
Why is a condenser microphone so much more sensitive than a dynamic microphone?
A condenser mic's diaphragm has very low mass, therefore it can move much faster than a dynamic mic's diaphragm which has much grater mass.
Why is a condenser microphone so much more sensitive than a dynamic microphone?
A condenser mic's diaphragm has very low mass, therefore it can move much faster than a dynamic mic's diaphragm which has much greater mass Because of the smaller diaphragm
A typical mono channel input will have all of the following input jacks. (Select all that apply) A. Balanced Microphone Input (XLR) B. Balanced Line Level (TRS) C. Insert Jack (TRS) D. Unbalanced 1/4 jack (TS) E. Channel Output (XLR)
A. Balanced Microphone Input (XLR) B. Balanced Line Level (TRS) C. Insert Jack (TRS)
Select all of the following attributes of a parametric equalizer. A. adjustable Q B. Fixed Q C. Adjustable Frequency D. Fixed Frequency E. Adjustable Gain F. Fixed Gain
A. adjustable Q C. Adjustable Frequency E. Adjustable Gain
Which of the following is/are a primary function of a mixer? (choose all that apply) A. mix audio signals B. route audio signals C. process audio signals
A. mix audio signals B. route audio signals C. process audio signals
Allows the engineer to listen to the audio from a channel with relative mix and panning levels in his/her headphones.
AFL
(blank 1) is used to prevent dropouts caused by radio cancelations at the antennas when using wireless microphones. Additionally, it is best practice to separate the antenna by a minimum of (blank 2) wavelength.
Acceptable answers for BLANK-1 are Diversity, multiple antenna, multiple antennae, multiple antennas, and antennas Acceptable answers for BLANK-2 are one half, 1/2, half, and half a
(blank) is important because it measure the noise created at each channel's preamp. If it is too high the console will have a large amount of noise when adding each channel together at the main outputs.
Acceptable answers for BLANK-1 are EIN and Equivalent Input Noise
A (blank) is a mixer with the speaker's amplifier built into it.
Acceptable answers for BLANK-1 are powered mixer, powered mixers, and powered
What is one of the easiest ways to reduce the effects of early reflections from side walls when placing loudspeakers in a room?
Aim speakers inward Tow your speakers.
The best way to prevent plosives in a microphone is to... A. remove frequencies below 80 hz with a high pass filter. B. move the microphone out of the direct path of the plosive. C. move the mic back by at least 8 cm. D. use an omnidirectional microphone to reduce proximity effect and, therefore, the plosives. E. All of the Above
All of the Above
Describe the difference between a bus and a DCA.
Allows remote control of channel faders but cannot combine signals Bus is for sending individual channels, VCA is for remote control of other faders.
Define Non-destructive solo.
Allows temporary focus on specific elements You solo and the other channels don't cut out.
To place an EQ, compressor, or other external audio device onto a channel on my mixer I need to use a...
An Insert cable consisting of one TRS to two TS connectors
An output that sends various combinations of the input signals to off-board processing equipment.
Auxiliary Sends
Where is a passive crossover placed in the signal flow of a drive rack?
Between the speaker and the amp after the power-amp, inside of the speaker
Name 2 of the jacks given for each input channel on an analog console.
Balanced microphone input (XLR)Balanced line level (TRS)Insert Jack (TRS) Mic input, Line input
What happens when you substitute a smaller cable (signal cable) for use on a speaker? A. You increase the impedance of the cable and, therefore, run the risk of burning out the amp. B. Your sound will lose all tone/definition in the low frequencies. C. Both of the above answers are true. D. None of the provided answers are true
Both of the above answers are true.
Box 5 is located: Box 9 is located: Box 7 is located:
Box 5 is located: Down Stage Box 9 is located: Stage Right Wing Box 7 is located: Thrust
A shared electrical conductor for multiple audio signals to be mixed together, then accessed and processed from a single channel.
Busses or Subgroups
What mic(s) best rejects sound from the back?
Cardioid
What mic(s) take advantage of a "port" to create their polar pattern?
Cardioid, Super cardioid
What Mic(s) are subject to proximity effect?
Cardioid, Super cardioid, Bidirectional
If I say to place the microphone up-stage center, where am I asking you to put it?
Center of stage / nearest back of stage Back of the stage in the center
Splitting a signal into two copies and inverting one copy while being transmitted through a cable in an effort to prevent signal interference describes:
Common mode rejection
Sense vocal ensembles are spread out over a larger area it is typically best to use two _____ microphones because of their sensitivity.
Condenser
Which microphone type requires a small built-in amplifier to amplify the voltage fluctuations from a sound source before it is sent to the mixer?
Condenser
List the 4 major components of a drive-rack in the most common signal flow they are placed into.
Console - EQ - Compressor - Active Crossover - Delay
___ is a graphic EQ where the bandwidth of each filter does not change when the slider is moved.
Constant-Q
When would you use a DI box and what does a DI box do?
Converts an unbalanced line or speaker level signal to a balanced microphone level signal/ provides impedance matching functions Converts unbalanced signal to balanced.
When an audio signal induces current into a cable lying next to it.
Cross talk
When miking a sound source near a reflective surface, such as miking a person at a podium, the sound can reflect off of the surface an create phase interference known as comb filtering. An approach to solve this problem is... A. to move the microphone as close to the sound source as practically possible. B. to use two microphones to eliminate the comb filtering. C. to replace the microphone with a boundary microphone. D. options a. and c.
D. ) options A and C
What effect does the audience have on the perception of sound in a space? A.) people absorb high frequency energy B.) the type of clothing people wear will affect how much sound is absorbed C.) the sound in a room can change based on the audience members sitting or standing D.) all of the above E.) none of the above
D.) all of the above
Interference created by electrical signals or fields.
EMI
What is the term given to the lead engineer on a show?
FOH
______ is the term used to refer to the equipment or resources whose primary function is to provide audio coverage to the main audience area.
Front of House (FOH)
What does the term FOH refer to?
Front of house / live engineer for the audience
Name and define one of the three common types of distortion.
Harmonic Distortion - Adding overtones that are whole number multiples of the fundamental. Harmonic: new frequencies added to the output that were not present in the input signal
The margin of dB you have between the average working signal level and the maximum signal level the system can handle is called:
Headroom
Energy absorbed by acoustic panels is released as...
Heat
impedance is the total opposition that an electronic device gives to alternating current.
Impedance
What are the 5 types of sound systems covered in class?
Installed PA, Portable PA, Personal, Band PA, Touring/Stadium PA
What are the 4 primary requirements of sound reinforcement?
Intelligibility, Fidelity, Power, Monitoring/Controllability - fidelity - intelligibility - power- controllability
The required reading for this class is...
Introduction to Live Sound Reinforcement by Teddy Boyce
Finish this statement: Early is on time, on time is...
Late
Digital processing is a serial process of several discrete steps where each step takes a small
Latency
List 3 advantages of a permanently installed sound system.
Less wear and tear, Easier to operate, Don't have to move it.
Describe the difference between a bus and a matrix send.
Matrix : For additional routing Bus : Combine Channels / Routing to outputs / Duplicate Signals Buses are for individual channel. Matrix is for outputs (bus matrix)
Select the answer below that places the following items in order to complete a basic signal flow for a sound reinforcement system.
Microphone, Mixer/Console, Effects Processors, Power Amplifier, Speaker
A line level, and typically pre-fader output used to feed headphones and/or a speaker on the stage for the band.
Monitor Outputs
Why do we prefer to use parametric EQ's rather than Graphic EQ's in our drive-rack?
More phase coherence
Describe how to change the routing of a channel from the stereo bus to bus 3 on the Midas Venice:
Press bus 3-4 switch and pan Left on channel Deselect a master send on a channel, then select 3-4 send on channel, then pan to left.
What Mic(s) will equally respond to sound from all directions?
Omni directional
How could you split or copy a signal on the Midas Venice?
Only put the TRS cable in halfway
Match the pins on an XLR to their correct wiring. Pin 1 pin 2 pin 3
Pin 1- Shield/Ground pin 2- Hot (+) pin 3- Cold (-)
What is the Pin Out of an XLR Connector?
Pin 1- Shield/Ground pin 2- Hot (+) pin 3- Cold (-) 1 - chassis ground (cable shield) 2 - hot (+); positive polarity terminal for balanced audio circuits 3 - cold (-); negative polarity terminal for balanced audio circuits
Which of the following items are not a primary requirement for a sound system?
Portability
What control is typically found at the top of a channel strip on a mixer?
Preamp / gain Trim
An increase in the low frequency response of a microphone as a user moves very close to the diaphragm is the definition of...
Proximity Effect
Interference created by radio signals.
RFI
What does it mean when I say I am using a split snake?
Sending it to different outputs
What is the advantage to setting up your Subs on an Aux send?
So you can control which instruments are sent to the subs.
What does a powered mixer have built into it that a non-powered mixer does not?
Speaker Amplifier/ power amplifier
Two mono channels that typically only accept line level inputs, and are managed by one set of controls.
Stereo Channel
What are the two main types of transducer in a sound system?
The input and output transducers Microphones and Speakers
Which description below describes the Power Alley the best?
The line between two speakers where both are in phase.
What do you hear in your headphones when soloing in AFL mode:
The mix that is sent to the mains Relative mix of the faders and panning
What is the definition of sound reinforcement?
The process of manipulating and amplifying sound for the purpose of allowing a small source to be heard and understood in and over an area that the source, by itself, would be incapable of covering adequately
Feedback is a result of:
The sound emitted from the loudspeaker entering the microphone, progressing through the electronic processors, and out the speaker again
When using an insert cable, the Tip and the Ring on the TRS connector are used do what?
Tip = send Ring - receive signal
What is the purpose of a limiter in the signal flow of a drive rack?
To prevent damage to the speakers. To protect your equipment
Name one of the three uses for an EQ in the Drive Rack:
To prevent feedback.
A line array is more commonly used in which type of PA system?
Touring P.A.
What component of a microphone splitter prevents phantom power from traveling back down the line to other mixers?
Transformer
What is the typical symbol for an amplifier?
Triangle
ORTF is a stereo near coincident technique using two cardioid microphones placed at a 110 degree angle.
True
Speaker wire has two conductors but no shielding is needed.
True
When referring to reverberation, early reflections are sounds that arrive within the first 80ms of the direct sound and add to the perceived loudness of the sound.
True
A fader that controls signal levels at multiple channels with a voltage, but never actually combines the audio onto one shared electrical conductor.
VCA
What is a distributed system?
a PA that reaches/ can connect to multiple spaces and rooms Playback throughout an entire building in multiple rooms.
What does it mean if I have an absorption coefficient of 0.04 at 2kHz?
a sound wave of 2kHz hits a material and 4% of that sound is being absorbed
What is one of the easiest ways to reduce the effects of early reflections from side walls when placing loudspeakers in a room?
aim the speakers inward (a.k.a. Toe-In)
Which of the following are connections and/or switches found on a DI box? A. Parallel output/Amplifier output B. Balanced XLR Output C. Pad Switch D. Ground Lift E. All of the above F. None of the above
all of the above
A ___ is an EQ that leaves all frequencies in tact but allows us to manipulate the phase of our audio signal.
all-pass filter
A chorus effect needs to do two crucial things, delay a copy of the signal and add a flanging effect into that copy.
false
A good way to quickly assess the early reflective properties of a room is to excite the acoustics of the room by whistling.
false
A stage plot shows the location of the Main PA's Left and Right speakers.
false
An Unbalanced cable uses three conductors while a balanced cable only uses two conductors.
false
In order to split an audio signal to two mixers, a passive or Y splitter is used to prevent noise from increasing on our microphone signal.
false
It is easier to absorb low frequency sounds than it is to absorb high frequency sounds.
false
Post Fader sends are always used for monitors and Pre Fader sends are always used for effects.
false
When a compressor has a high ratio and long release time you may hear the level of the audio rise and fall. This effect is called breathing.
false
Which type of cable shielding is used for permanent installations?
foil
In general when frequency ________, wave length ________.
goes up, decreases
What happens to the energy absorbed by an acoustic Panel?
he energy absorbed is dissipated as heat It turns into heat
The ____ of a room gives us information about the intensity of reflections, or reverberation, inside the space.
impulse response
What does 0 on a VU meter represent?
nominal operating level- (+4)dBu- when signals are averaging around the 0VU point there is about 20dB of headroom Nominal level, +4 dBU
What type of noise signal, that is equal energy per octave, is most commonly used to assess speaker performance?
pink noise
the striking of a sound against a large flat object that propagates the energy at an angle equal to the angle of incidence.
reflection
What is the polar pattern of the Shure Beta 57?
supercardioid
Define the ripple effect as it pertains to microphones.
the left over momentum of the diaphragm after the transient Leftover movement after original transient
The Terms NL2, NL4, NL8 refer to...
the number of conductors you have inside a speakon connector and cable.
A sound system is more likely to have reflection issues when...
the room has a lot of hard materials in it such as wood or stone
A compressor set to have "brick wall" limiting will have a ratio of...
∞:1
