Signal Processing

Question 1

Three Types of Basic Signal Processing Equipment

Answer 1

Frequency Domain
Dynamic Processors
Time Based (Enhancers)

Question 2

Cut-Off Frequency

Answer 2

Point where signal has dropped -3dB

Question 3

Slope Order Rate

Answer 3

Slope is at a constant rate
✤ First order: 6 dB/8va
✤ Second order: 12 dB/8va
✤ Third order: 18 dB/8va

Question 4

Notch Filters

Answer 4

✤ Very narrow band - normally to attenuate problems
✤ 60 Hz hum
✤ Usually covers the 2nd harmonic (octave) as well

Question 5

Shelving Equalizer

Answer 5

The response rises or falls then levels out
Identified by the Turnover Frequency
This is the point levels out
3 dB before the maximum amount of boost or attenuation

Question 6

Peaking Equalization

Answer 6

Stated by it’s center frequency
✤ Bandwidth
✤ Expressed as Q (quality factor)

Question 7

Parametric Equalization

Answer 7

Frequency selection is variable
over a wide band
✤ Variable amplitude
✤ Variable Q
✤ Sometimes switch selectable

Question 8

Graphic Equalizers

Answer 8

✤ Gives a Graphic display
✤ Each band is peaking type EQ
✤ Bandwidth is not adjustable
✤ Narrow bandwidth
Based on International Standards Organization 
Octaves to 1/6 octaves

Question 9

Passive EQ

Answer 9

does not amplify
Passive elements attenuate the signal around the audio band to be boosted
Phase shift due to the use of inductors and capacitors
Fixed gain raised the entire audio band

Question 10

Active EQ

Answer 10

Amplifier

Question 11

Gain Riding

Answer 11

Manual Compression

Question 12

Electronic Gain Riding

Answer 12

An electronic circuit whose gain varies automatically as a function of the input signal

Question 13

Compressor

Answer 13

A variable gain amplifer in which the dynamic range of the output signal is less than that of the applied input signal

Question 14

CompressionAttack time

Answer 14

The time it takes for compression to begin

Question 15

Compression Release Time

Answer 15

The time it takes the out put to restore itself

to unity gain

Question 16

Breathing or Pumping

Answer 16

A great fluctuation around the threshold will cause a rise and fall of background noise

A fast release time can be a problem with
pumping and breathing

Question 17

Limiter

Answer 17

A compressor with a ratio of 8:1 or greater

Question 18

Expanders

Answer 18

A variable gain amplifer in which the dynamic range of the output signal is greater than that of the applied input signal

Question 19

Noise Gate

Answer 19

An expander whose parameters are set to sharply attenuate an input channel

Question 20

Key Input

Answer 20

Allows an external source to trigger the output of an compressor/ limiter or expander/gate through a side chain

Question 21

De-Esser

Answer 21

Am equalizer is inserted into the CV side chain of a compressor

Question 22

Soundfield

Answer 22

A complex combination of direct and reflected energy that exists in a living environment
✤ Time delay
    Direct to reflected energy ratio
✤ Sound level (placement)
✤ Frequency response
✤ Visual cues

Question 23

Direct sound

Answer 23

The sound wave travels in a straight path to the listener

✤ no way to simulate this

Question 24

Echo

Answer 24

✤ A single repetition that arrives some time after the direct sound
✤ Delay is the time it takes for a discrete echo

Question 25

Decay

Answer 25

The attenuation of sound field over time

Question 26

Early Reflections

Answer 26

✤ A few closely spaced echoes that arrive shortly after the direct sound

Question 27

Reverberation

Answer 27

✤ As time goes on more and more echoes arrive

✤ The echoes are so close it is impossible to distinguish them from one another

Question 28

Reverberation Time

Answer 28

✤ The time it takes for the reverberation to decrease 60 dB

Question 29

Time Delay systems

Answer 29

✤ A system that can store a signal and reproduce it after a suitable time

Question 30

Haas Effect (1949)

Answer 30

✤ 0 - 10 ms: Image shift (The delayed speaker will have to be raised
about 10 dB)
✤ 10 - 30 ms: Sound from the primary source, sense the delay but not
the direction
✤ 30 - 50 ms: Become aware of the delay
✤ 50 ms and up: Primary source and discrete echo
✤ These are all approximate and vary with the sound and application

Question 31

Tape Delay

Answer 31

t sec = d in/s in/sec

Question 32

Analog Shift Register (Bucket Brigade)

Answer 32

✤ Transfers a charge from one capacitor (register) to the next
✤ Problems
✤ Residual loss
✤ transfer loss
✤ thermal semi-conductor charge loss

Question 33

Spring Reverberation

Answer 33

Developed by the Hammond Organ Co.

Question 34

Plate Reverberation

Answer 34

✤ Dr. Walter Kuhl (1957) Institute
of Broadcasting Technology,
Hamburg
✤ Excite a steel plate with a
transducer
✤ 1/64” thick and 6’ X 3’
✤ Two pickups
✤ 3:1 rule

Question 35

Digital Reverberation

Answer 35

Simulates all aspects in the digital domain

Question 36

Pitch Change

Answer 36

✤ Signal is sampled at one rate and then played back at another
rate
✤ To keep the original length …
✤ … samples must be removed to lower the pitch
✤ … samples need to be added to raise the pitch

Question 37

Flanging

Answer 37

✤ With a delayed replica some frequencies are reinforced while others are canceled as a result of time shifts.
✤ Time shift varies resulting in a sweep up and down the frequency spectrum

Question 38

Phasing

Answer 38

An attempt to duplicate the effect of flanging using a phase shift network
Move a notch filter with a high ‘Q’
Depth= how for the center frequency, oves
Speed= how quick the movement is
Phasing is not as apparent as flanging

Question 39

Aural Exciters

Answer 39

Excites even order harmonics

Newer units allow control of both even and odd harmonics

Question 40

Time Compression/Expansion

Answer 40

✤ Lengthens or shortens the duration of a signal with no change in pitch