HW 2: Sound Reproduction Systems

An RCA cable is capable of eliminating interference in an analog signal via principles of balanced audio.

false

The signal produced by a microphone is a balanced audio signal.

true

Rank the following signal level standardizations based on their relative voltage level. 1 is lowest, 4 is highest.

• instrument level

• mic level

• line level

• speaker level

mic level, instrument level, line level, speaker level

Which of the following statements about AC and DC are true? Check all that apply.

A) AC and DC are freely interchangeable.

B) A DAC is used to convert AC to DC.

C) DC is faster and more accurate than AC.

D) AC is used to represent analog audio signals.

E) AC periodically reverses flow direction.

D, E

A ribbon microphone is a type of capacitor microphone.

false

What does ADC stand for? ______________________

analog-to-Digital Converter

Imagine that you see the label “+4 dBu” on the main output jacks of an analog mixer. What does this label signify?

A) The output signal voltage is 4 dB greater than typical line level.

B) The output signal voltage is at consumer line level.

C) The output signal voltage is at professional line level.

D) The mixer's output signal will be unbalanced.

E) The output signal of the mixer has a high impedance.

C

A variable gain mixer can be used to adjust an instrument level signal so that it is roughly equal to line level.

true

Which of the following statements are NOT true about direct injection boxes? Check all that apply.

A) They convert monophonic signals to stereophonic signals.

B) They convert low impedance signals to high impedance signals.

C) They convert high impedance signals to low impedance signals.

D) They convert instrument level to line level.

E) They convert instrument level to mic level.

A, B, D

Passive loudspeakers expect line level input.

false

What is the purpose of a preamplifier?

A) To amplify a sound before it encounters a microphone's diaphragm.

B) To prevent accidental damage to analog equipment.

C) To prevent an unbalanced signal from picking up unwanted interference.

D) To raise a mic level signal to line level.

E) To raise a line level signal to speaker level.

D

Imagine you are looking straight into a female XLR connector, oriented so that the holes are at 3, 6, and 9 o'clock (imagine the connector is a clock face). Which hole corresponds to ground?

A) cannot be determined

B) the pin at 3 o'clock

C) the pin at 9 o'clock

D) the pin at 6 o'clock

B

Despite having physical faders/knobs and often having the appearance of a mixer, a ____________ does not route or process audio signals; instead, it sends MIDI data to software running on a computer, which is where signal routing and processing actually takes place.

control surface

The voice coil, magnet, and diaphragm inside of a dynamic microphone are collectively called the microphone's ____________.

capsule

The voice coil, magnet, and cone within a loudspeaker are collectively called the loudspeaker's ____________.

driver

Condenser microphones are also called _________________ microphones.

A) capacitor

B) cardioid

C) electret

D) dynamic

E) ribbon

A

Generally speaking, moving-coil dynamic microphones are robust; they can handle fairly loud sound sources and tolerate some physical abuse.

true

Which of the following microphone sensitivity patterns indicate equal sensitivity to sound sources directly in front AND directly behind the microphone? Select all that apply.

A) hypercardioid

B) bidirectional

C) cardioid

D) omnidirectional

B, D

The ___________________ is an increase in low frequency level that occurs when a sound source is very close to a microphone (within about 2 feet). This effect only occurs with directional microphones and increases in severity as microphone directionality increases.

Correct answer:

proximity effect

Loudspeaker circuitry that divides a full-spectrum audio signal into multiple, discrete frequency bands is called a ______________.

crossover

Which of the following are commonly found on an analog mixer input channel strip? Select all that apply.

A) auxiliary send knob

B) DI box

C) pan knob

D) reverb/delay effects

E) TOSLINK jack

F) equalizer controls

A, C, F

In the context of professional audio applications, an external digital audio interface is usually necessary because most modern computers do not have built-in analog-to-digital and digital-to-analog converters.

false

Which of the following are you most likely to see on an AC volt meter when measuring the output level of a full-volume tone coming out of your laptop?

A) 150 V

B) 0.15 mV

C) 1.5 V

D) 15 V

E) 1.5 mV

F) 15 mV

C

A ____________ converts energy from one form to another.

transducer

Condenser microphones can operate with or without an external DC power supply.

false

The word "analog" is used to describe analog audio signals because the voltage patterns in electrical signals used to represent sound waves are directly analogous to corresponding pressure patterns in the air.

true

Why is the voltage of a microphone signal so relatively low?

A) the energy in sound waves is only powerful enough to move a microphone diaphragm a tiny bit, resulting in a low-voltage signal.

B) it would create undesirable interference patterns between the signal and the phantom power supply.

C) the impedance of a preamplifier counteracts the microphone transduction process.

D) the proximity effect prevents microphones from outputting high-level signals.

A

How does balanced circuitry allow devices to reject unwanted signal interference?

A) devices send multiple redundant copies of a signal and pass the one that has the least amount of interference contamination.

B) devices perform a spectrum analysis and apply spectral filtering to identify and remove unwanted interference.

C) devices sum a signal with an inverted copy in order to nullify interference picked up along each wire.

D) devices transmit signals at an extremely high level to improve signal-to-noise ratio, rendering low-level interference negligible.

C

A stereo signal transmitted to headphones via a single TRS connection consists of two balanced monophonic signals.

false

Why do most loudspeakers have multiple drivers?

A) multiple drivers provide a more realistic stereo image.

B) a single driver/cone cannot radiate all audible frequencies with equal efficiency; multiple drivers of different sizes provide a more complete representation of the audible spectrum.

C) multiple drivers provide redundant copies in case one driver fails.

D) multiple drivers vibrate in phase with each other, improving the structural integrity of the loudspeaker housing.

E) multiple drivers look more impressive than a single-driver loudspeaker.

B