Sound Reinforcement Final Exam Actual Questions and
Answers
What is sound reinforcement?
Process of manipulating & amplifying sound over an area that the source, by itself,
would not be capable of covering adequately.
Primary requirements of a sound reinforcement system
Intelligibility, Fidelity, Power, and Monitoring and Controllability
Secondary requirements of a sound reinforcement system
Portability, longevity, and flexibility
Basic sound system model
Input transducers - signal processors - output transducers
What is natural sound?
Unprocessed sound
What is a Transducer?
Device that captures the sound and gets it into a form that the system can process.
What is a Transformer?
A ___ is a static electrical device that transfers electrical energy between two or more
circuits.
Fixed Installation
For venues with regular sound needs
Portable P.A.
Can be taken from one location to another
Personal P.A.
Smallest; can usually fit into a car
Range of 10-20 ft.
Band P.A.
Designed to reinforce small to large venues
Easily scalable
Best for groups of 10-2,000 people
Tour/Stadium P.A.
Extreme end of PA systems
Requires small army of people & trucks
Use same components - just more & bigger versions
Needs more set up time & knowledge
What are three common types of distortions?
1. Overdriven sound
2. Harmonic Distortions
3. Intermodulation
What constitutes "the sound environment"?
The collection of objects, conditions, and circumstances in which the sound system
operates and with which it interacts.
What are the three major conditions that the environment can affect?
,1. Affects how we, as engineers, hear
2. Affects the perceived performance of the system
3. Affects how the audience hears
Sound waves are by nature ___ waves.
longitudinal
We use 2D graphical representation of sound waves known as ___ waves.
Transverse
What is Reflection?
Interactions with solid surfaces and objects in the environment
What is Diffusion?
Reflections from a rough or irregular surface. Reflective energy is propagated in many
directions.
What is Reverberation?
Sounds reflected from various surfaces
Early Reflections
<80ms
Persistent Reflections
≥100ms
RT60
The amount of time it takes the reverberation of a room to decay 60dB below the initial
SPL of the direct sound.
What is Absorption?
___ occurs because the energy carried by the wave, which was previously used to
displace air molecules, is now being used to displace the molecules of that object. It
takes more energy to displace the molecules of the object than of air.
What is the Absorption Coefficient?
Ranges from 0-1, with a "1" being 100% absorptive.
A material has an absorption coefficient of 0.15 at 500Hz. What does that mean?
The material absorbs 15% of the sound at 500Hz.
What is Diffraction?
The change in direction of travel of a wave due to interaction with an object.
What does it mean to "toe in" a set of speakers, and why is this considered "best
practice" in sound reinforcement?
It is how the speakers are angled towards the main listening position. If the speakers
are angled inward >< then that means they are "toe in". That way the sound is directed
towards the listener.
What is inside a Microphone?
Transducer
What is inside a DI Box?
Transformer
What are the two main types of transducers in a sound reinforcement system?
Dynamic and Condenser
What does a balanced connection mean?
A ___ has three conductors in the connector and three wires in the cable: two signals
wires plus a separate ground wire.
___ use two signal wires; both carry a copy of the signal, but the two copies are sent
, with their polarity reversed. If you sum two signals that are identical but are reversed in
polarity, the signals cancel out, leaving you with silence.
What is a unbalanced connection?
An ___ consists of two connectors with two conductors each, connected by two wires
inside the cable—a signal wire and a ground wire.
Typical line level signal in professional audio is ___ dBu.
+4
Typical microphone level signal is between ___ dBV and ___ dBV.
-60 and -40
What is the pinout for an unbalanced 1/4" connector?
Tip-Ring
What is the pinout for a balanced 1/4" connector?
Tip: Left positive
Ring: Right positive
Sleeve: Cable shield
What is the pinout for an XLR connector?
Pin 1: Ground
Pin 2: Positive
Pin 3: Negative
What is the pinout for an RCA jack?
Ring: (Right Channel)
Sleeve: (Ground)
Tip: (Left Channel)
Sleeve: (Ground)
What does a DI Box do?
A ___ converts an unbalanced line or speaker level signal to a balanced microphone
level signal.
It also provides impedance matching functions.
What is an Active DI Box?
An ___ contains active electronic components that require a power source. Power is
provided either in the form of batteries, a wall power adapter, or phantom power from
the mixer.
What is a Passive DI Box?
A ___ does not require any power to operate and consists only of a transformer and
some resistors.
What is phantom power and what is it used for?
___ is used to power a microphone that needs power to operate.
Which pins on an XLR cable provide phantom power?
When phantom power is tuned on at the mixer, +48V is supplied to pins 2 and 3 of the
XLR plug of the microphone. These are the same pins on which the audio signal travels.
Is an insert send/return cable balanced or unbalanced?
The tip is the effects send signal (unbalanced), the ring is the effects return signal
(unbalanced), and the sleeve is the common ground for send and return.
Cables are rated according to use
Current & Voltage
What is Cable Shielding?
Answers
What is sound reinforcement?
Process of manipulating & amplifying sound over an area that the source, by itself,
would not be capable of covering adequately.
Primary requirements of a sound reinforcement system
Intelligibility, Fidelity, Power, and Monitoring and Controllability
Secondary requirements of a sound reinforcement system
Portability, longevity, and flexibility
Basic sound system model
Input transducers - signal processors - output transducers
What is natural sound?
Unprocessed sound
What is a Transducer?
Device that captures the sound and gets it into a form that the system can process.
What is a Transformer?
A ___ is a static electrical device that transfers electrical energy between two or more
circuits.
Fixed Installation
For venues with regular sound needs
Portable P.A.
Can be taken from one location to another
Personal P.A.
Smallest; can usually fit into a car
Range of 10-20 ft.
Band P.A.
Designed to reinforce small to large venues
Easily scalable
Best for groups of 10-2,000 people
Tour/Stadium P.A.
Extreme end of PA systems
Requires small army of people & trucks
Use same components - just more & bigger versions
Needs more set up time & knowledge
What are three common types of distortions?
1. Overdriven sound
2. Harmonic Distortions
3. Intermodulation
What constitutes "the sound environment"?
The collection of objects, conditions, and circumstances in which the sound system
operates and with which it interacts.
What are the three major conditions that the environment can affect?
,1. Affects how we, as engineers, hear
2. Affects the perceived performance of the system
3. Affects how the audience hears
Sound waves are by nature ___ waves.
longitudinal
We use 2D graphical representation of sound waves known as ___ waves.
Transverse
What is Reflection?
Interactions with solid surfaces and objects in the environment
What is Diffusion?
Reflections from a rough or irregular surface. Reflective energy is propagated in many
directions.
What is Reverberation?
Sounds reflected from various surfaces
Early Reflections
<80ms
Persistent Reflections
≥100ms
RT60
The amount of time it takes the reverberation of a room to decay 60dB below the initial
SPL of the direct sound.
What is Absorption?
___ occurs because the energy carried by the wave, which was previously used to
displace air molecules, is now being used to displace the molecules of that object. It
takes more energy to displace the molecules of the object than of air.
What is the Absorption Coefficient?
Ranges from 0-1, with a "1" being 100% absorptive.
A material has an absorption coefficient of 0.15 at 500Hz. What does that mean?
The material absorbs 15% of the sound at 500Hz.
What is Diffraction?
The change in direction of travel of a wave due to interaction with an object.
What does it mean to "toe in" a set of speakers, and why is this considered "best
practice" in sound reinforcement?
It is how the speakers are angled towards the main listening position. If the speakers
are angled inward >< then that means they are "toe in". That way the sound is directed
towards the listener.
What is inside a Microphone?
Transducer
What is inside a DI Box?
Transformer
What are the two main types of transducers in a sound reinforcement system?
Dynamic and Condenser
What does a balanced connection mean?
A ___ has three conductors in the connector and three wires in the cable: two signals
wires plus a separate ground wire.
___ use two signal wires; both carry a copy of the signal, but the two copies are sent
, with their polarity reversed. If you sum two signals that are identical but are reversed in
polarity, the signals cancel out, leaving you with silence.
What is a unbalanced connection?
An ___ consists of two connectors with two conductors each, connected by two wires
inside the cable—a signal wire and a ground wire.
Typical line level signal in professional audio is ___ dBu.
+4
Typical microphone level signal is between ___ dBV and ___ dBV.
-60 and -40
What is the pinout for an unbalanced 1/4" connector?
Tip-Ring
What is the pinout for a balanced 1/4" connector?
Tip: Left positive
Ring: Right positive
Sleeve: Cable shield
What is the pinout for an XLR connector?
Pin 1: Ground
Pin 2: Positive
Pin 3: Negative
What is the pinout for an RCA jack?
Ring: (Right Channel)
Sleeve: (Ground)
Tip: (Left Channel)
Sleeve: (Ground)
What does a DI Box do?
A ___ converts an unbalanced line or speaker level signal to a balanced microphone
level signal.
It also provides impedance matching functions.
What is an Active DI Box?
An ___ contains active electronic components that require a power source. Power is
provided either in the form of batteries, a wall power adapter, or phantom power from
the mixer.
What is a Passive DI Box?
A ___ does not require any power to operate and consists only of a transformer and
some resistors.
What is phantom power and what is it used for?
___ is used to power a microphone that needs power to operate.
Which pins on an XLR cable provide phantom power?
When phantom power is tuned on at the mixer, +48V is supplied to pins 2 and 3 of the
XLR plug of the microphone. These are the same pins on which the audio signal travels.
Is an insert send/return cable balanced or unbalanced?
The tip is the effects send signal (unbalanced), the ring is the effects return signal
(unbalanced), and the sleeve is the common ground for send and return.
Cables are rated according to use
Current & Voltage
What is Cable Shielding?
