Audio Effects II

Andrés Cabrera

MAT 200B

Types of effects

• Spectral effects
• Dynamic range effects
• Time delay effects and Reverb
• Others

Time delay

Tape Delay

Tape Delay

Tape Delay

Time delay

• Parameters
• Delay time
• Feedback
• Multi-tap delays offer multiple delay times
• Can be used with long delays
• Clear echos, sometimes synchronized to tempo
• Or very short delays
• "slap-back" effect
  

Digital time delay

Digital time delay

• "Perfect"
• Tape delay has:
• distortion
• wow
• flutter
• high noise floor
• (which can be emulated digitally)
  

Reverb

Sound propagation

Sound field

Impulse Response

Frequency and reverb

"Acoustic" reverb

Artificial Reverb

• Close microphones and small rooms produce the necessity for artificial reverb.

Reverb chamber

Plate reverb

Spring reverb

Mechanical reverbs

Digital reverbs

• Reverbs can be modeled as many delays
• Adding feedback can lead to economic digital models
• Schroeder proposed the first digital reverb in the 1960s.

Schroeder reverb

Digital reverb

• Many digital reverbs related to the Schroeder reverb have been developed in the past decades
• Famous ones include the Alesis QuadraVerb and the Lexicon reverbs

Digital reverb

Reverb parameters

Modulating delays

Flanger/Chorus

Convolution reverb

An impulse response can be "applied"

to a signal through convolution

Convolution is a mathematical process

that makes the source sound

as if it had been played where the IR

was taken

(Assuming linearity and time-invariance)

http://www.kvraudio.com/forum/viewtopic.php?t=107337

Convolution Reverb

http://www.youtube.com/watch?v=SN8XUrObX0c

Other effects

• Auto-tune
• Melodyne
• Time stretching
  

http://www.youtube.com/watch?v=9OUgXFZ_WeY