Signal Theory quiz

Question 1

LAW: The phase of the wave inverts

Answer 1

Reflection

Question 2

LAW: Transfer of wave energy into another substance that does not vibrate

Answer 2

Absorption

Question 3

LAW: Wave splits into more waves when it hits convex or concave surfaces

Answer 3

Diffusion

Question 4

LAW: Waves sound differently as they travel through different mediums

Answer 4

Refraction

Question 5

LAW: Waves can bend around corners

Answer 5

Diffraction

Question 6

Complex pattern of reflections created by sound in an enclosed space

Answer 6

Interference Pattern

Question 7

What make up the Interference Pattern?

Answer 7

Nodes (wave crests) and anti-nodes (wave troughs)

Question 8

Time relationship created when sound arrives at your ears

Answer 8

Phase

Question 9

Speed of sound (1127 ft/sec) divided by frequency (cycles/sec) =

Answer 9

Wavelength (in feet)

Question 10

When two or more mics are employed to pick up the same signal, but because of placement, the same signal arrives out of phase/time. When two identical sound waves are present and one waveform is 180 degrees

Answer 10

Phase cancellation

Question 11

Sound envelope

Answer 11

Attack, decay, sustain, release, or silence.

Note: Complex envelopes may have several instances of Attack and Decay

Question 12

Frequency response

Answer 12

Sensitivity to frequency or bandwidth

Question 13

Dynamic range

Answer 13

Sound pressure level measured subjectively in decibels/SPL from soft to loud

Question 14

Addition or subtraction of gain (amplitude) for small selected bands of frequencies to obtain desired results

Answer 14

Equalization

Question 15

Pitch

Answer 15

Musical term for frequency (cycles per second)

Question 16

Compression/Rarefaction

Answer 16

Increase over the norm in pressure/decrease below the normal pressure

Question 17

To weaken or rarefy a signal, normally accomplished by increasing impedance

Answer 17

Attenuate

Question 18

Transmission of power from one form of energy to another

Answer 18

Transducer

Question 19

Transient

Answer 19

Sudden and abrupt, normally undesirable signal or voltage/trigger voltage/spike in attack of square wave

Question 20

Sibilance

Answer 20

Portion of speech that requires high frequency bandwidth; hiss

Question 21

Noise

Answer 21

All frequencies, at equal levels, averaged over time (Aperiodic Motion)

Question 22

Equal Loudness Theorem

Answer 22

Human hearing does NOT exhibit flat frequency response

Question 23

Nyquist Theorem

Answer 23

In order to recover all four components of a periodic waveform, it is necessary to sample more than twice as fast as the highest waveform frequency

Question 24

Nyquist frequency (or Nyquist limit)

Answer 24

The highest frequency that can be coded at a given sampling rate, in order to be able to fully reconstruct the signal

Question 25

Unbalanced signal

Answer 25

Two conductor wiring RCA phono or Tip-Sleeve (TS) connectivity: program(+) and ground shield(-); can only extend about 30-40 ft before signal deterioration

Question 26

Consumer Line Level Signal

Answer 26

An unbalanced, high impedance signal employing RCA phono or Tip-Sleeve (TS) connectivity

Question 27

Noise canceling method of signal transmission employing XLR or Tip-Ring-Sleeve (TRS) connector using three-conductor wiring, shield, or ground

Answer 27

Balanced signal

Question 28

Professional mic/line level; Consumer line level; Speaker level

Answer 28

+4dB. 1.23 volts @ 600 ohms. 3 wire conductors. -10dB. .77 volts @ 10,000 ohms. 2 wire conductors. 2 -100 volts possible. 2 -32 ohms. 2 conductors.

Question 29

An increase in low frequency response when a mic is very close to the sound source

Answer 29

Proximity Effect

Question 30

What's the threshold of hearing?

Answer 30

0 dB SPL of a young and undamaged ear

Question 31

What's the threshold of pain?

Answer 31

Between 120 and 130 (phons or dB SPL) measured at 1 Khz

Question 32

DSP stands for

Answer 32

Digital Signal Processing

Question 33

Gain-based DSP

Answer 33

Equalization, gating, compression/limiting, normalizing, filtering

Question 34

Time-based DSP

Answer 34

Reverb, delay, chorusing, flanging, phasing, doppler

Question 35

Inverse Square Law

Answer 35

The intensity of the sound (dB SPL) varies with the distance; for each doubling of distance (in m) from the source, the SPL will drop by 6 dB

Question 36

Impedance measured in ohms

Answer 36

Resistance. | Note: Adding resistance/impedance attenuates a signal

Question 37

Phenomenon: This occurs as electrons gravitate toward the "empty wire" or lowest energy state

Answer 37

Inductance

Question 38

The ability to retain or store an electrical charge (measured in farads); the basic working principle of a condenser mic

Answer 38

Capacitance

Question 39

Form of interference caused by presence of several sounds with similar frequency content, in the same space

Answer 39

Masking

Question 40

Modulation types

Answer 40

Amplitude modulation (AM); Frequency modulation (FM); Ring modulation (RM)

Question 41

Polar field patterns

Answer 41

Case of speaker: Patterns of radiation. Case of mic: Patterns of sensitivity. - Omnidirectional, uni-directional, cardioid, hyper-cardioid, super cardioid, bi-directional, and ellipsoidal

Question 42

Piezo Element

Answer 42

Basic, high impedance, signal inducing transducer. Bi-directional

Question 43

Ceramic mic

Answer 43

Older mic elements used in early telephone technology and phonograph pickups

Question 44

Dynamic mic

Answer 44

Uses inductance as a vehicle to pick up waves of compression/rarefaction

Question 45

Condenser mic

Answer 45

Uses capacitance to bias the backplate/diaphragm, producing wide range and high freq sensitivity

Question 46

Ribbon mic

Answer 46

Light, thin, corrugated piece of metal foil is used to produce a warm, rich, and full freq response

Question 47

PZM and PCC mics

Answer 47

Pressure Zone Mic (PZM) is omnidirectional that looks down at boundary, while Phase Coherent Cardioid (PCC) mic has supercardioid capsule and looks across the boundary

Question 48

The human ear can hear

Answer 48

20-20,000 Hz

Question 49

Periodic motion vs. Aperiodic motion

Answer 49

Periodic - 4 natural harmonic waveforms (sine, triangle, sawtooth, square) - timbre - perceived intellectually Aperiodic - noise - all frequencies have equal volumes - perceived inwardly

Question 50

Four natural harmonic waveforms

Answer 50

Sine: very few harmonics Triangle: odd harmonics Sawtooth: odd/even harmonics Square: even harmonics